Journal articles: 'Nitrates – Reactivity'

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González-Sánchez, Juan Miguel, Nicolas Brun, Junteng Wu, Julien Morin, Brice Temime-Roussel, Sylvain Ravier, Camille Mouchel-Vallon, Jean-Louis Clément, and Anne Monod. "On the importance of atmospheric loss of organic nitrates by aqueous-phase ●OH oxidation." Atmospheric Chemistry and Physics 21, no. 6 (March 30, 2021): 4915–37. http://dx.doi.org/10.5194/acp-21-4915-2021.

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Abstract. Organic nitrates are secondary species in the atmosphere. Their fate is related to the chemical transport of pollutants from polluted areas to more distant zones. While their gas-phase chemistry has been studied, their reactivity in condensed phases is far from being understood. However, these compounds represent an important fraction of organic matter in condensed phases. In particular, their partition to the aqueous phase may be especially important for oxidized organic nitrates for which water solubility increases with functionalization. This work has studied for the first time the aqueous-phase ⚫OH-oxidation kinetics of four alkyl nitrates (isopropyl nitrate, isobutyl nitrate, 1-pentyl nitrate, and isopentyl nitrate) and three functionalized organic nitrates (α-nitrooxyacetone, 1-nitrooxy-2-propanol, and isosorbide 5-mononitrate) by developing a novel and accurate competition kinetic method. Low reactivity was observed, with kOH ranging from 8×107 to 3.1×109 L mol−1 s−1 at 296±2 K. Using these results, a previously developed aqueous-phase structure–activity relationship (SAR) was extended, and the resulting parameters confirmed the extreme deactivating effect of the nitrate group, up to two adjacent carbon atoms. The achieved extended SAR was then used to determine the ⚫OH-oxidation rate constants of 49 organic nitrates, including hydroxy nitrates, ketonitrates, aldehyde nitrates, nitrooxy carboxylic acids, and more functionalized organic nitrates such as isoprene and terpene nitrates. Their multiphase atmospheric lifetimes towards ⚫OH oxidation were calculated using these rate constants, and they were compared to their gas-phase lifetimes. Large differences were observed, especially for polyfunctional organic nitrates: for 50 % of the proposed organic nitrates for which the ⚫OH reaction occurs mainly in the aqueous phase (more than 50 % of the overall removal), their ⚫OH-oxidation lifetimes increased by 20 % to 155 % under cloud/fog conditions (liquid water content LWC = 0.35 g m−3). In particular, for 83 % of the proposed terpene nitrates, the reactivity towards ⚫OH occurred mostly (>98 %) in the aqueous phase, while for 60 % of these terpene nitrates, their lifetimes increased by 25 % to 140 % compared to their gas-phase reactivity. We demonstrate that these effects are of importance under cloud/fog conditions but also under wet aerosol conditions, especially for the terpene nitrates. These results suggest that considering aqueous-phase ⚫OH-oxidation reactivity of biogenic nitrates is necessary to improve the predictions of their atmospheric fate.

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Rindelaub, Joel D., Carlos H. Borca, Matthew A. Hostetler, Jonathan H. Slade, Mark A. Lipton, Lyudmila V. Slipchenko, and Paul B. Shepson. "The acid-catalyzed hydrolysis of an α-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact." Atmospheric Chemistry and Physics 16, no. 23 (December 13, 2016): 15425–32. http://dx.doi.org/10.5194/acp-16-15425-2016.

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Abstract. The production of atmospheric organic nitrates (RONO2) has a large impact on air quality and climate due to their contribution to secondary organic aerosol and influence on tropospheric ozone concentrations. Since organic nitrates control the fate of gas phase NOx (NO + NO2), a byproduct of anthropogenic combustion processes, their atmospheric production and reactivity is of great interest. While the atmospheric reactivity of many relevant organic nitrates is still uncertain, one significant reactive pathway, condensed phase hydrolysis, has recently been identified as a potential sink for organic nitrate species. The partitioning of gas phase organic nitrates to aerosol particles and subsequent hydrolysis likely removes the oxidized nitrogen from further atmospheric processing, due to large organic nitrate uptake to aerosols and proposed hydrolysis lifetimes, which may impact long-range transport of NOx, a tropospheric ozone precursor. Despite the atmospheric importance, the hydrolysis rates and reaction mechanisms for atmospherically derived organic nitrates are almost completely unknown, including those derived from α-pinene, a biogenic volatile organic compound (BVOC) that is one of the most significant precursors to biogenic secondary organic aerosol (BSOA). To better understand the chemistry that governs the fate of particle phase organic nitrates, the hydrolysis mechanism and rate constants were elucidated for several organic nitrates, including an α-pinene-derived organic nitrate (APN). A positive trend in hydrolysis rate constants was observed with increasing solution acidity for all organic nitrates studied, with the tertiary APN lifetime ranging from 8.3 min at acidic pH (0.25) to 8.8 h at neutral pH (6.9). Since ambient fine aerosol pH values are observed to be acidic, the reported lifetimes, which are much shorter than that of atmospheric fine aerosol, provide important insight into the fate of particle phase organic nitrates. Along with rate constant data, product identification confirms that a unimolecular specific acid-catalyzed mechanism is responsible for organic nitrate hydrolysis under acidic conditions. The free energies and enthalpies of the isobutyl nitrate hydrolysis intermediates and products were calculated using a hybrid density functional (ωB97X-V) to support the proposed mechanisms. These findings provide valuable information regarding the organic nitrate hydrolysis mechanism and its contribution to the fate of atmospheric NOx, aerosol phase processing, and BSOA composition.

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Bew, Sean P., Glyn D. Hiatt-Gipson, Graham P. Mills, and Claire E. Reeves. "Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate." Beilstein Journal of Organic Chemistry 12 (May 27, 2016): 1081–95. http://dx.doi.org/10.3762/bjoc.12.103.

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Here we report the chemoselective synthesis of several important, climate relevant isoprene nitrates using silver nitrate to mediate a ’halide for nitrate’ substitution. Employing readily available starting materials, reagents and Horner–Wadsworth–Emmons chemistry the synthesis of easily separable, synthetically versatile ‘key building blocks’ (E)- and (Z)-3-methyl-4-chlorobut-2-en-1-ol as well as (E)- and (Z)-1-((2-methyl-4-bromobut-2-enyloxy)methyl)-4-methoxybenzene has been achieved using cheap, ’off the shelf’ materials. Exploiting their reactivity we have studied their ability to undergo an ‘allylic halide for allylic nitrate’ substitution reaction which we demonstrate generates (E)- and (Z)-3-methyl-4-hydroxybut-2-enyl nitrate, and (E)- and (Z)-2-methyl-4-hydroxybut-2-enyl nitrates (‘isoprene nitrates’) in 66–80% overall yields. Using NOESY experiments the elucidation of the carbon–carbon double bond configuration within the purified isoprene nitrates has been established. Further exemplifying our ‘halide for nitrate’ substitution chemistry we outline the straightforward transformation of (1R,2S)-(−)-myrtenol bromide into the previously unknown monoterpene nitrate (1R,2S)-(−)-myrtenol nitrate.

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Romanova, Svetlana M., and Liliya A. Fatykhova. "INVESTIGATION OF REACTIONS OF INTERACTION OF CELLULOSE NITRIC ESTERS WITH CARBOXYLIC ACID CHLORIDES." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, no. 5 (May 13, 2021): 30–34. http://dx.doi.org/10.6060/ivkkt.20216405.6313.

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The chemical interaction of high-nitrogen cellulose ether with acetic, propionic, butyric and isobutyric acids has been studied. The general laws and features of the electrophilic substitution of functional groups of cellulose nitroesters are revealed. The preferred directions of the chemical interaction of cellulose nitrate with carboxylic acid chlorides are established: O-acylation of nitrate and hydroxyl groups; O-acylation of the glucopyranose ring; O-acylation of the ether bond with depolymerization of the chain of an SC molecule; hydrolysis of nitrate groups; destruction of the chain of a macromolecule of nitric acid ester with the formation of water-soluble organic compounds. The structure, properties and possibilities of using synthesized mixed cellulose ethers were studied. Effective methods have been developed for the chemical modification of cellulose nitrates with carboxylic acid chlorides. The probable directions of the reaction of the interaction of cellulose nitrates with electrophilic reagents are predicted based on quantum-chemical calculations of point charges on the atoms of the reacting molecules. The reactivity of highly substituted cellulose nitrates in reactions with carboxylic acid chlorides has been established. The optimal conditions for the interaction of cellulose nitrates with carboxylic acid chlorides have been identified and a mathematical model of the reaction kinetics has been constructed. The possibility of a directed change in the composition of chemically modified cellulose nitrates depending on the synthesis conditions has been established. As a result of the combined use of physicochemical research methods, the chemical composition was determined and the structure of the synthesized compounds was determined: cellulose acetyl nitrates, cellulose propionyl nitrates, cellulose butyryl nitrates, and cellulose isobutyryl nitrates. Using gel chromatography, it was found that the molecular weight characteristics of the synthesized samples are directly dependent on the conditions of their synthesis. It was found that electrophilic substitution of the functional groups of cellulose nitrate proceeds more intensively in the pyridine medium.

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Liebmann, Jonathan, Nicolas Sobanski, Jan Schuladen, Einar Karu, Heidi Hellén, Hannele Hakola, Qiaozhi Zha, et al. "Alkyl nitrates in the boreal forest: formation via the NO3-, OH- and O3-induced oxidation of biogenic volatile organic compounds and ambient lifetimes." Atmospheric Chemistry and Physics 19, no. 15 (August 15, 2019): 10391–403. http://dx.doi.org/10.5194/acp-19-10391-2019.

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Abstract. The formation of alkyl nitrates in various oxidation processes taking place throughout the diel cycle can represent an important sink of reactive nitrogen and mechanism for chain termination in atmospheric photo-oxidation cycles. The low-volatility alkyl nitrates (ANs) formed from biogenic volatile organic compounds (BVOCs), especially terpenoids, enhance rates of production and growth of secondary organic aerosol. Measurements of the NO3 reactivity and the mixing ratio of total alkyl nitrates (ΣANs) in the Finnish boreal forest enabled assessment of the relative importance of NO3-, O3- and OH-initiated formation of alkyl nitrates from BVOCs in this environment. The high reactivity of the forest air towards NO3 resulted in reactions of the nitrate radical, with terpenes contributing substantially to formation of ANs not only during the night but also during daytime. Overall, night-time reactions of NO3 accounted for 49 % of the local production rate of ANs, with contributions of 21 %, 18 % and 12 % for NO3, OH and O3 during the day. The lifetimes of the gas-phase ANs formed in this environment were on the order of 2 h due to efficient uptake to aerosol (and dry deposition), resulting in the transfer of reactive nitrogen from anthropogenic sources to the forest ecosystem.

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Lockwood, A. L., P. B. Shepson, M. N. Fiddler, and M. Alaghmand. "Isoprene nitrates: preparation, separation, identification, yields, and atmospheric chemistry." Atmospheric Chemistry and Physics 10, no. 13 (July 8, 2010): 6169–78. http://dx.doi.org/10.5194/acp-10-6169-2010.

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Abstract. Isoprene is an important atmospheric volatile organic compound involved in ozone production and NOx (NO+NO2) sequestration and transport. Isoprene reaction with OH in the presence of NO can form either isoprene hydroxy nitrates ("isoprene nitrates") or convert NO to NO2 which can photolyze to form ozone. While it has been shown that isoprene nitrate production can represent an important sink for NOx in forest impacted environments, there is little experimental knowledge of the relative importance of the individual isoprene nitrate isomers, each of which has a different fate and reactivity. In this work, we have identified the 8 individual isomers and determined their total and individual production yields. The overall yield of isoprene nitrates at atmospheric pressure and 295 K was found to be 0.070(+0.025/−0.015). Three isomers, representing nitrates resulting from OH addition to a terminal carbon, represent 90% of the total IN yield. We also determined the ozone rate constants for three of the isomers, and have calculated their atmospheric lifetimes, which range from ~1–2 h, making their oxidation products likely more important as atmospheric organic nitrates and sinks for nitrogen.

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Ren, Qiang, Xiu Lan Wu, and Xuan Meng He. "Effects of Adding Form of Additives on the Structure and Properties of High-Purity Alumina Ceramics." Key Engineering Materials 336-338 (April 2007): 1130–32. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.1130.

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High-purity alumina ceramics was prepared using high-purity α-Al2O3 powder as raw material, nitrates or oxides of magnesium, chromium and copper as additives by a wet ball milling with a later dry pressing forming and normal pressure sintering process. The influence of additives on the sintering temperature, microstructure and bending strength of the prepared alumina ceramics was studies. The results showed that the additive doped with nitrate can be dispersed uniformly in the body with molecule scale, and the oxides obtained by decomposing of nitrates have the higher reactivity. Thus, the nitrate additives have better capacity than oxide additives in reducing the sintering temperature and inhibiting the abnormal grain growth, and the alumina ceramics prepared by adding of nitrate additives have higher density and bending strength.

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Perring, A. E., T. H. Bertram, P. J. Wooldridge, A. Fried, B. G. Heikes, J. Dibb, J. D. Crounse, et al. "Airborne observations of total RONO2: new constraints on the yield and lifetime of isoprene nitrates." Atmospheric Chemistry and Physics Discussions 8, no. 3 (June 24, 2008): 12313–41. http://dx.doi.org/10.5194/acpd-8-12313-2008.

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Abstract. Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments indicate that formation rates of isoprene nitrates are uncertain to a factor of 2–3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunction nitrates (ΣANs), NO2, total peroxy nitrates (ΣPNs), HNO3, H2CO, isoprene and other VOC were obtained from the NASA DC-8 aircraft during summer 2004 over the continental US during the INTEX-NA campaign. These observations represent the first characterization of ΣANs over a wide range of land surface types and in the free troposphere. ΣANs were a significant, 12–20%, fraction of NOy throughout the experimental domain and ΣANs were more abundant when isoprene was high. We use the observed VOC to calculate the relative contributions of ΣAN precursors to their production. These calculations indicate that isoprene represents at least 76% of the ΣAN source in the summertime continental boundary layer of the US. An observed correlation between ΣANs and CH2O is used to place constraints on nitrate yields from isoprene oxidation, atmospheric lifetimes of the resulting nitrates and recycling efficiencies of nitrates during subsequent oxidation. We recommend sets of production rates, lifetimes and recycling efficiencies of INs as follows [4.4%, 5 h, 92%], [8%, 2.5 h, 84%] and [12%, 90 min, 74%]. The analysis indicates that the lifetime of ΣANs as a pool of compounds is considerably longer than the lifetime of the individual isoprene nitrates to reaction with OH, implying that the organic nitrate functionality is at least partially maintained through a second oxidation cycle.

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Lockwood, A. L., P. B. Shepson, M. N. Fiddler, and M. Alaghmand. "Isoprene nitrates: preparation, separation, identification, yields, and atmospheric chemistry." Atmospheric Chemistry and Physics Discussions 10, no. 4 (April 22, 2010): 10625–51. http://dx.doi.org/10.5194/acpd-10-10625-2010.

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Abstract. Isoprene is an important atmospheric volatile organic compound involved in ozone production and NOx (NO+NO2) sequestration and transport. Isoprene reaction with OH in the presence of NO can form either isoprene nitrates or convert NO to NO2 which can photolyze to form ozone. While it has been shown that isoprene nitrate production can represent an important sink for NOx in forest impacted environments, there is little experimental knowledge of the relative importance of the individual isoprene nitrate isomers, each of which has a different fate and reactivity. In this work, we have identified the 8 individual isomers and determined their total and individual production yields. The overall yield of isoprene nitrates at atmospheric pressure and 295 K was found to be 0.070(+0.025/–0.015). Three isomers, the (4,3)-IN, (1,2)-IN and Z-(4,1)-IN represent 90% of the total IN yield. We also determined the ozone rate constants for three of the isomers, and have calculated their atmospheric lifetimes, which range from ~1–2 h, making their oxidation products likely more important as atmospheric organic nitrates and sinks for nitrogen.

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Perring, A. E., T. H. Bertram, P. J. Wooldridge, A. Fried, B. G. Heikes, J. Dibb, J. D. Crounse, et al. "Airborne observations of total RONO2: new constraints on the yield and lifetime of isoprene nitrates." Atmospheric Chemistry and Physics 9, no. 4 (February 23, 2009): 1451–63. http://dx.doi.org/10.5194/acp-9-1451-2009.

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Abstract. Formation of isoprene nitrates (INs) is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. Isoprene nitrates also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Current assessments indicate that formation rates of isoprene nitrates are uncertain to a factor of 2–3 and the subsequent fate of isoprene nitrates remains largely unconstrained by laboratory, field or modeling studies. Measurements of total alkyl and multifunctional nitrates (ΣANs), NO2, total peroxy nitrates (ΣPNs), HNO3, CH2O, isoprene and other VOC were obtained from the NASA DC-8 aircraft during summer 2004 over the continental US during the INTEX-NA campaign. These observations represent the first characterization of ΣANs over a wide range of land surface types and in the lower free troposphere. ΣANs were a significant, 12–20%, fraction of NOy throughout the experimental domain and ΣANs were more abundant when isoprene was high. We use the observed hydrocarbon species to calculate the relative contributions of ΣAN precursors to their production. These calculations indicate that isoprene represents at least three quarters of the ΣAN source in the summertime continental boundary layer of the US. An observed correlation between ΣANs and CH2O is used to place constraints on nitrate yields from isoprene oxidation, atmospheric lifetimes of the resulting nitrates and recycling efficiencies of nitrates during subsequent oxidation. We find reasonable fits to the data using sets of production rates, lifetimes and recycling efficiencies of INs as follows (4.4%, 16 h, 97%), (8%, 2.5 h, 79%) and (12%, 95 min, 67%). The analysis indicates that the lifetime of ΣANs as a pool of compounds is considerably longer than the lifetime of the individual isoprene nitrates to reaction with OH, implying that the organic nitrate functionality is at least partially maintained through a second oxidation cycle.

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Budaeva, Vera V., Yulia A. Gismatulina, Galina F. Mironova, Ekaterina A. Skiba, Evgenia K. Gladysheva, Ekaterina I. Kashcheyeva, Olga V. Baibakova, et al. "Bacterial Nanocellulose Nitrates." Nanomaterials 9, no. 12 (November 27, 2019): 1694. http://dx.doi.org/10.3390/nano9121694.

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Bacterial nanocellulose (BNC) whose biosynthesis fully conforms to green chemistry principles arouses much interest of specialists in technical chemistry and materials science because of its specific properties, such as nanostructure, purity, thermal stability, reactivity, high crystallinity, etc. The functionalization of the BNC surface remains a priority research area of polymers. The present study was aimed at scaled production of an enlarged BNC sample and at synthesizing cellulose nitrate (CN) therefrom. Cyclic biosynthesis of BNC was run in a semisynthetic glucose medium of 10−72 L in volume by using the Medusomyces gisevii Sa-12 symbiont. The most representative BNC sample weighing 6800 g and having an α-cellulose content of 99% and a polymerization degree of 4000 was nitrated. The nitration of freeze-dried BNC was performed with sulfuric-nitric mixed acid. BNC was examined by scanning electron microscopy (SEM) and infrared spectroscopy (IR), and CN was explored to a fuller extent by SEM, IR, thermogravimetric analysis/differential scanning analysis (TGA/DTA) and 13C nuclear magnetic resonance (NMR) spectroscopy. The three-cycle biosynthesis of BNC with an increasing volume of the nutrient medium from 10 to 72 L was successfully scaled up in nonsterile conditions to afford 9432 g of BNC gel-films. CNs with a nitrogen content of 10.96% and a viscosity of 916 cP were synthesized. It was found by the SEM technique that the CN preserved the 3D reticulate structure of initial BNC fibers a marginal thickening of the nanofibers themselves. Different analytical techniques reliably proved the resultant nitration product to be CN. When dissolved in acetone, the CN was found to form a clear high-viscosity organogel whose further studies will broaden application fields of the modified BNC.

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Fouqueau, Axel, Manuela Cirtog, Mathieu Cazaunau, Edouard Pangui, Jean-François Doussin, and Bénédicte Picquet-Varrault. "A comparative and experimental study of the reactivity with nitrate radical of two terpenes: α-terpinene and γ-terpinene." Atmospheric Chemistry and Physics 20, no. 23 (December 8, 2020): 15167–89. http://dx.doi.org/10.5194/acp-20-15167-2020.

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Abstract. Biogenic volatile organic compounds (BVOCs) are intensely emitted by forests and crops into the atmosphere. During the night, they react very rapidly with the nitrate radical (NO3), leading to the formation of a variety of functionalized products including organic nitrates and to large amounts of secondary organic aerosols (SOAs). Organic nitrates (ONs) have been shown not only to play a key role in the transport of reactive nitrogen and consequently in the ozone budget but also to be important components of the total organic-aerosol mass, while SOAs are known to play a direct and indirect role in the climate. However, the reactivity of BVOCs with NO3 remains poorly studied. The aim of this work is to provide new kinetic and mechanistic data for two monoterpenes (C10H16), α- and γ-terpinene, through experiments in simulation chambers. These two compounds, which have very similar chemical structures, have been chosen in order not only to overcome the lack of experimental data but also to highlight the influence of the chemical structure on the reactivity. Rate constants have been measured using both relative and absolute methods. They were found to be (1.2±0.5)×10-10 and (2.9±1.1)×10-11 cm3 molecule−1 s−1 for α- and γ-terpinene respectively. Mechanistic studies have also been conducted in order to identify and quantify the main reaction products. Total organic nitrate and SOA yields have been determined. While organic nitrate formation yields appear to be similar, SOA yields exhibit large differences with γ-terpinene being a much more efficient precursor of aerosols. In order to provide explanations for this difference, chemical analysis of the gas-phase products was performed at the molecular scale. Detected products allowed for proposing chemical mechanisms and providing explanations through peroxy and alkoxy reaction pathways.

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Xiong, Fulizi, Carlos H. Borca, Lyudmila V. Slipchenko, and Paul B. Shepson. "Photochemical degradation of isoprene-derived 4,1-nitrooxy enal." Atmospheric Chemistry and Physics 16, no. 9 (May 4, 2016): 5595–610. http://dx.doi.org/10.5194/acp-16-5595-2016.

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Abstract. In isoprene-impacted environments, carbonyl nitrates are produced from NO3-initiated isoprene oxidation, which constitutes a potentially important NOx reservoir. To better understand the fate of isoprene carbonyl nitrates, we synthesized a model compound, trans-2-methyl-4-nitrooxy-2-buten-1-al (4,1-isoprene carbonyl nitrate, or 4,1-isoprene nitrooxy enal), and investigated its photochemical degradation process. The measured OH and O3 oxidation rate constants (298 K) for this nitrooxy enal are 4.1(±0.7) × 10−11 cm3 molecules−1 s−1 and 4.4(±0.3) × 10−18 cm3 molecules−1 s−1, respectively. Its UV absorption spectrum was determined, and the result is consistent with TDDFT calculations. Based on its UV absorption cross section and photolysis frequency in a reaction chamber, we estimate that the ambient photolysis frequency for this compound is 3.1(±0.8) × 10−4 s−1 for a solar zenith angle of 45°. The fast photolysis rate and high reactivity toward OH lead to a lifetime of less than 1 h for the isoprene nitrooxy enal, with photolysis being a dominant daytime sink. The nitrate products derived from the OH oxidation and the photolysis of the nitrooxy enal were identified with an iodide-based chemical ionization mass spectrometer. For the OH oxidation reaction, we quantified the yields of two nitrate products, methyl vinyl ketone nitrate and ethanal nitrate, which together contributed to 36(±5) % of the first-generation products.

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Jurišová, Jana, Pavel Fellner, and Ladislav Pach. "Characteristics of Sorel cement prepared from impure materials." Acta Chimica Slovaca 8, no. 2 (October 1, 2015): 87–90. http://dx.doi.org/10.1515/acs-2015-0015.

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Abstract Production of potassium nitrate from potassium chloride and magnesium nitrate is related with the production of by-product, which is water solution of MgCl2 having concentration (24-30) mass %. Along with magnesium chloride this solution contains also nitrates and potassium and calcium cations. This solution can be used as defrosting agent or as a component for the production of building material based on Sorel cement. Sorel cement is material originating from the reaction of MgCl2 solution with solid MgO of suitable reactivity which depends on the temperature of calcinations of MgCO3 and size of MgO particles. Sorel cement paste is prepared by mixing MgO and MgCl2 in molar ratio 9 : 1 with the addition of water in appropriate amount. This cement settles in 2 hours and it can be treated within 24 hours, depending on the reactivity of MgO. This paper deals with the preparation and properties| of Sorel cement made of by-product (MgCl2) from the production of fertilizer KNO3 and MgO prepared from Slovak magnesite (Jelsava) with high content of impurities. We will show that properties of this material are suitable for application in building industry.

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Perring, A. E., T. H. Bertram, D. K. Farmer, P. J. Wooldridge, J. Dibb, N. J. Blake, D. R. Blake, et al. "The production and persistence of ΣRONO2 in the Mexico City plume." Atmospheric Chemistry and Physics 10, no. 15 (August 6, 2010): 7215–29. http://dx.doi.org/10.5194/acp-10-7215-2010.

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Abstract. Alkyl and multifunctional nitrates (RONO2, ΣANs) have been observed to be a significant fraction of NOy in a number of different chemical regimes. Their formation is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. ΣANs also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Numerous studies have investigated the role of nitrate formation from biogenic compounds and in the remote atmosphere. Less attention has been paid to the role ΣANs may play in the complex mixtures of hydrocarbons typical of urban settings. Measurements of total alkyl and multifunctional nitrates, NO2, total peroxy nitrates (ΣPNs), HNO3 and a representative suite of hydrocarbons were obtained from the NASA DC-8 aircraft during spring of 2006 in and around Mexico City and the Gulf of Mexico. ΣANs were observed to be 10–20% of NOy in the Mexico City plume and to increase in importance with increased photochemical age. We describe three conclusions: (1) Correlations of ΣANs with odd-oxygen (Ox) indicate a stronger role for ΣANs in the photochemistry of Mexico City than is expected based on currently accepted photochemical mechanisms, (2) ΣAN formation suppresses peak ozone production rates by as much as 40% in the near-field of Mexico City and (3) ΣANs play a significant role in the export of NOy from Mexico City to the Gulf Region.

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Farmer, D. K., A. E. Perring, P. J. Wooldridge, D. R. Blake, A. Baker, S. Meinardi, L. G. Huey, D. Tanner, O. Vargas, and R. C. Cohen. "Impact of organic nitrates on urban ozone production." Atmospheric Chemistry and Physics 11, no. 9 (May 4, 2011): 4085–94. http://dx.doi.org/10.5194/acp-11-4085-2011.

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Abstract. Urban O3 is produced by photochemical chain reactions that amplify background O3 in mixtures of gaseous nitrogen oxides (NOx) and organic molecules. Current thinking treats NOx and organics as independent variables that limit O3 production depending on the NOx to organic ratio; in this paradigm, reducing organics either has no effect or reduces O3. We describe a theoretical counterexample where NOx and organics are strongly coupled and reducing organics increases O3 production, and illustrate the example with observations from Mexico City. This effect arises from chain termination in the HOx and NOx cycles via organic nitrate production. We show that reductions in VOC reactivity that inadvertently reduce organic nitrate production rates will be counterproductive without concurrent reductions in NOx or other organics.

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Kumar, Amit. "Dissolving pulp production: Cellulases and xylanases for the enhancement of cellulose accessibility and reactivity." Physical Sciences Reviews 6, no. 5 (April 30, 2021): 111–29. http://dx.doi.org/10.1515/psr-2019-0047.

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Abstract Dissolving pulps are high-grade cellulose pulps that have minimum amount of non-cellulosic impurities. Dissolving pulps are the basic source for the manufacturing of several cellulosic products such as viscose, lyocell, cellulose acetates, cellulose nitrates, carboxymethyl-cellulose, etc. Dissolving pulps are mainly manufactured by pre-hydrolysis kraft and acid sulphite pulping. A high reactivity of dissolving pulps is desirable for its eco-friendly utilization for several purposes. Several approaches including mechanical, chemical, ultrasonic, and enzymatic treatments have been employed for the improvement of pulp reactivity. This review mainly focussed on pulp reactivity improvement through enzymatic approaches. Cellulases and xylanase have been proved effective for the improvement of pulp reactivity of dissolving pulp from different sources. The different combinations of cellulase, xylanase, and mechanical refining have been tested and found more effective rather than the single one.

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Slade, Jonathan H., Chloé de Perre, Linda Lee, and Paul B. Shepson. "Nitrate radical oxidation of γ-terpinene: hydroxy nitrate, total organic nitrate, and secondary organic aerosol yields." Atmospheric Chemistry and Physics 17, no. 14 (July 17, 2017): 8635–50. http://dx.doi.org/10.5194/acp-17-8635-2017.

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Abstract. Polyolefinic monoterpenes represent a potentially important but understudied source of organic nitrates (ONs) and secondary organic aerosol (SOA) following oxidation due to their high reactivity and propensity for multi-stage chemistry. Recent modeling work suggests that the oxidation of polyolefinic γ-terpinene can be the dominant source of nighttime ON in a mixed forest environment. However, the ON yields, aerosol partitioning behavior, and SOA yields from γ-terpinene oxidation by the nitrate radical (NO3), an important nighttime oxidant, have not been determined experimentally. In this work, we present a comprehensive experimental investigation of the total (gas + particle) ON, hydroxy nitrate, and SOA yields following γ-terpinene oxidation by NO3. Under dry conditions, the hydroxy nitrate yield = 4(+1/−3) %, total ON yield = 14(+3/−2) %, and SOA yield ≤ 10 % under atmospherically relevant particle mass loadings, similar to those for α-pinene + NO3. Using a chemical box model, we show that the measured concentrations of NO2 and γ-terpinene hydroxy nitrates can be reliably simulated from α-pinene + NO3 chemistry. This suggests that NO3 addition to either of the two internal double bonds of γ-terpinene primarily decomposes forming a relatively volatile keto-aldehyde, reconciling the small SOA yield observed here and for other internal olefinic terpenes. Based on aerosol partitioning analysis and identification of speciated particle-phase ON applying high-resolution liquid chromatography–mass spectrometry, we estimate that a significant fraction of the particle-phase ON has the hydroxy nitrate moiety. This work greatly contributes to our understanding of ON and SOA formation from polyolefin monoterpene oxidation, which could be important in the northern continental US and the Midwest, where polyolefinic monoterpene emissions are greatest.

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Shiu, Kom-Bei, Luh-Tin Yang, Shih-Wei Jean, Chien-Hsing Li, Ru-Rong Wu, Ju-Chun Wang, Lin-Shu Liou, and Michael Y. Chiang. "Syntheses, Structures, and Reactivity of Diruthenium Phosphine Carbonyl Complexes of Nitrites and Nitrates." Inorganic Chemistry 35, no. 26 (January 1996): 7845–49. http://dx.doi.org/10.1021/ic960530p.

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Chen, Hai-Ying, Zhehao Wei, Marton Kollar, Feng Gao, Yilin Wang, Janos Szanyi, and Charles H. F. Peden. "NO oxidation on zeolite supported Cu catalysts: Formation and reactivity of surface nitrates." Catalysis Today 267 (June 2016): 17–27. http://dx.doi.org/10.1016/j.cattod.2015.11.039.

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21

Wenzel, P., U. Hink, M. Oelze, A. Seeling, T. Isse, K. Bruns, L. Steinhoff, et al. "Number of nitrate groups determines reactivity and potency of organic nitrates: a proof of concept study in ALDH-2−/− mice." British Journal of Pharmacology 150, no. 4 (February 2007): 526–33. http://dx.doi.org/10.1038/sj.bjp.0707116.

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22

Békássy, S., T. Cseri, G. Kenessey, G. Pokol, K. Tomor, and G. Liptay. "Correlation between the reactivity and the structural and thermal properties of supported metal nitrates." Journal of Thermal Analysis 40, no. 3 (September 1993): 1285–92. http://dx.doi.org/10.1007/bf02546892.

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23

Pérez, I. M., B. W. LaFranchi, and R. C. Cohen. "Nitrogen oxide chemistry in an urban plume: investigation of the chemistry of peroxy and multifunctional organic nitrates with a Lagrangian model." Atmospheric Chemistry and Physics Discussions 9, no. 6 (December 16, 2009): 27099–165. http://dx.doi.org/10.5194/acpd-9-27099-2009.

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Abstract. Air quality in the outflow from urban centers affects millions of people, as well as, natural and managed ecosystems downwind. In locations where there are large sources of biogenic VOCs downwind of urban centers, the outflow is characterized by a high VOC reactivity due to biogenic emissions and low NOx. However most field and chamber studies have focused on limiting cases of high NOx or of near zero NOx. Recent measurements of a wide suite of VOCs, O3 and meteorological parameters at several locations within the Sacramento urban plume have provided a detailed benchmark for testing our understanding of chemistry in a plume transitioning from high NOx to low NOx and high VOC reactivity. As an additional simplification, the strong mountain valley circulation in the region makes this urban plume a physical realization of a nearly idealized Lagrangian plume. Here, we describe a model of this plume. We use a Lagrangian model representing chemistry based on the Master Chemical Mechanism (MCM) v3.1 along with mixing and deposition. We discuss the effects of entrainment of background air, the branching ratio for the production of isoprene nitrates and the effects of soil NOx emissions on the composition of the evolving plume. The model predicts that after 2–3 h of chemical processing only 45% of the peroxynitrates (ΣPNs) are PAN and that most (69%) RONO2 are secondary alkyl nitrate products of the reaction of OH with RONO2. We find the model is more consistent with the observations if: a) the yield of ΣPNs from large and multi-functional aldehydes is close to zero; and b) the reaction between OH and RONO2 produces multifunctional nitrates as opposed to either HNO3 or NO2 as is typical in most currently adopted reaction mechanisms. Model results also show that adding NOx emissions throughout the transect increases the available NOx in the downwind regions, but modeled ozone concentrations were little affected by the increased NOx.

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Perring, A. E., T. H. Bertram, D. K. Farmer, P. J. Wooldridge, J. Dibb, N. J. Blake, D. R. Blake, et al. "Alkyl nitrate production and persistence in the Mexico City Plume." Atmospheric Chemistry and Physics Discussions 9, no. 6 (November 11, 2009): 23755–90. http://dx.doi.org/10.5194/acpd-9-23755-2009.

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Abstract. Alkyl and multifunctional nitrates (ΣANs) have been observed to be a significant fraction of NOy in a number of different chemical regimes. Their formation is an important free radical chain termination step ending production of ozone and possibly affecting formation of secondary organic aerosol. ΣANs also represent a potentially large, unmeasured contribution to OH reactivity and are a major pathway for the removal of nitrogen oxides from the atmosphere. Numerous studies have investigated the role of nitrate formation from biogenic compounds. Less attention has been paid to the role ΣANs may play in the complex mixtures of hydrocarbons typical of urban settings. Measurements of ΣANs, NO2, total peroxy nitrates (ΣPNs), HNO3 and a wide suite of hydrocarbons were obtained from the NASA DC-8 aircraft during spring of 2006 in and around Mexico City and the Gulf of Mexico. ΣANs were observed to be 10–20% of NOy in the Mexico City plume and to increase in importance with increased photochemical age. We describe three conclusions: 1) Correlations of ΣANs with odd-oxygen (Ox) indicate a stronger role for ΣANs in the photochemistry of Mexico City than is expected based on currently accepted photochemical mechanisms, 2) ΣAN formation suppresses peak ozone production rates by as much as 30% in the near-field of Mexico City and 3) ΣANs play a comparable role to ΣPNs in the export of NOy to the Gulf Region.

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Kosenko, Nadezhda F., Natalya V. Filatova, and Anastasia A. Egorova. "MAGNESIOCHROMITE (MgCr2O4) SYNTHESIS: EFFECT OF MECHANICAL AND MICROWAVE PRETREATMENT." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, no. 8 (June 24, 2020): 96–102. http://dx.doi.org/10.6060/ivkkt.20206308.6214.

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Magnesiochromite spinel synthesis based on oxides, hydroxides and nitrates of magnesium and chromium was investigated. The precursors reactivity was compared by means of effective rate constants calculated by Ginstling-Brounshtein equation. The possibility of use of this equation was confirmed by the dependences linearity with high linear approximation coefficients. The reactivity of MgO various forms (soft-burned, or caustic magnesite, and dead-burned, or periclase) in the spinel formation was compared. Oxide precursors (especially with the periclase participation) reacted with the substantially less rate in comparison with hydroxides and salts. The influence of a preliminary mechanical activation by impact-and-attrition (planetary mill) and attrition (ball-ring mill) action as well as a microwave treatment (2.45 GHz) was analyzed. The most positive effect of a mechanical treatment in a planetary mill that was associated with an activation of Mg and Cr compounds became apparent in the field of relatively low temperatures (700-1100 °С). For example, MgCr2O4 yield at 1000 °С and the joint impact treatment of oxides was twice as much than under the simple mixing. The subsequent temperature rising lead to some decrease of a pretreatment effect so long as diffusion coefficients in these conditions grew, so the reaction run rapidly even without a preliminary mechanical treatment. It was noticed that an appreciable reduction of MgO reactivity in the spinel formation after a certain attrition in a ball-ring mill linked to the plane sliding in cubic crystals and resulted in the removing of the most disordered and defective layer from grains and the plane surface uncovering. The combined method consisting of a mechanical treatment of magnesium and chromium nitrates mixture in a planetary mill and the subsequent burning in a thermal kiln (1000 °С) was considered as the most effective as it resulted in practically single product. The microwave treatment took up an intermediate position by the effectiveness.

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Liebmann, Jonathan M., Jennifer B. A. Muller, Dagmar Kubistin, Anja Claude, Robert Holla, Christian Plass-Dülmer, Jos Lelieveld, and John N. Crowley. "Direct measurements of NO3 reactivity in and above the boundary layer of a mountaintop site: identification of reactive trace gases and comparison with OH reactivity." Atmospheric Chemistry and Physics 18, no. 16 (August 22, 2018): 12045–59. http://dx.doi.org/10.5194/acp-18-12045-2018.

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Abstract. We present direct measurements of the summertime total reactivity of NO3 towards organic trace gases, kOTGNO3, at a rural mountain site (988 m a.s.l.) in southern Germany in 2017. The diel cycle of kOTGNO3 was strongly influenced by local meteorology with high reactivity observed during the day (values of up to 0.3 s−1) and values close to the detection limit (0.005 s−1) at night when the measurement site was in the residual layer and free troposphere. Daytime values of kOTGNO3 were sufficiently large that the loss of NO3 due to reaction with organic trace gases competed with its photolysis and reaction with NO. Within experimental uncertainty, monoterpenes and isoprene accounted for all of the measured NO3 reactivity. Averaged over the daylight hours, more than 25 % of NO3 was removed via reaction with biogenic volatile organic compounds (BVOCs), implying a significant daytime loss of NOx and the formation of organic nitrates due to NO3 chemistry. Ambient NO3 concentrations were measured on one night and were comparable to those derived from a stationary-state calculation using measured values of kOTGNO3. We present and compare the first simultaneous, direct reactivity measurements for the NO3 and OH radicals. The decoupling of the measurement site from ground-level emissions resulted in lower reactivity at night for both radicals, though the correlation between OH and NO3 reactivity was weak as would be anticipated given their divergent trends in rate constants with many organic trace gases.

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Bahadori, Elnaz, Francesco Conte, Antonio Tripodi, Gianguido Ramis, and Ilenia Rossetti. "Photocatalytic Selective Oxidation of Ammonia in a Semi-Batch Reactor: Unravelling the Effect of Reaction Conditions and Metal Co-Catalysts." Catalysts 11, no. 2 (February 5, 2021): 209. http://dx.doi.org/10.3390/catal11020209.

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Photocatalysis has been used for the oxidation of ammonia/ammonium in water. A semibatch photoreactor was developed for this purpose, and nanostructured TiO2-based materials, either commercial P25 or prepared by flame spray pyrolysis (FSP), were used as catalysts. In the present work, we investigated the effect of (i) metal co-catalysts, (ii) pH, and (iii) ammonia concentration on the efficiency of oxidation and on the selectivity to the undesired overoxidation byproduct, i.e., nitrites and nitrates. Several metals were added to both titania samples, and the physicochemical properties of every sample were studied by XRD, BET, and UV-Vis spectroscopy. The pH, which was investigated in the range of 2.5–11.5, was the most important parameter. The optimum pH values, resulted as 11.5 and 4.8 for P25 and FSP respectively, matching the best compromise between an acceptable conversion and a limited selectivity toward nitrite and nitrate formation. For both titania samples (P25 and FSP), ammonia conversion vs. nitrite and nitrate formation were highly dependent on the pH. At pH ≥ 9, the initial rate of photooxidation was high, with selective formation of overoxidized byproducts, whereas, at a more acidic pH, the conversion was lower, but the selectivity toward nitrogen formation was higher. P25 samples added with noble metal co-catalysts (0.1 mol% Ag, Au, Pd, Pt) at pH = 11.5 remarkably increased the selectivity to nitrite and nitrate, while, in the case of FSP samples (pH = 4.8), the co-catalysts increased the selectivity toward N2 with respect to the unpromoted catalyst and also the conversion in the case of Au and Pt. Reactivity was discussed, leading to the proposing of a mechanism that correlates the activity with either surface adsorption (depending of the surface charge of the catalyst and on pH) or the homogeneous reactivity of oxidizing species.

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Guillaume, D., J. Morvan, and G. Martin. "Influence of light on phenol compound reactivity in the presence of nitrates in abiotic solution." Environmental Technology Letters 10, no. 5 (May 1989): 491–500. http://dx.doi.org/10.1080/09593338909384765.

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Sadokhina, N. A., D. E. Doronkin, G. N. Baeva, S. Dahl, and A. Yu Stakheev. "Reactivity of Surface Nitrates in H2-Assisted SCR of NO x Over Ag/Al2O3 Catalyst." Topics in Catalysis 56, no. 9-10 (April 19, 2013): 737–44. http://dx.doi.org/10.1007/s11244-013-0033-2.

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Guo, Hao, Clare M. Flynn, Michael J. Prather, Sarah A. Strode, Stephen D. Steenrod, Louisa Emmons, Forrest Lacey, et al. "Heterogeneity and chemical reactivity of the remote troposphere defined by aircraft measurements." Atmospheric Chemistry and Physics 21, no. 18 (September 16, 2021): 13729–46. http://dx.doi.org/10.5194/acp-21-13729-2021.

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Abstract. The NASA Atmospheric Tomography (ATom) mission built a photochemical climatology of air parcels based on in situ measurements with the NASA DC-8 aircraft along objectively planned profiling transects through the middle of the Pacific and Atlantic oceans. In this paper we present and analyze a data set of 10 s (2 km) merged and gap-filled observations of the key reactive species driving the chemical budgets of O3 and CH4 (O3, CH4, CO, H2O, HCHO, H2O2, CH3OOH, C2H6, higher alkanes, alkenes, aromatics, NOx, HNO3, HNO4, peroxyacetyl nitrate, other organic nitrates), consisting of 146 494 distinct air parcels from ATom deployments 1 through 4. Six models calculated the O3 and CH4 photochemical tendencies from this modeling data stream for ATom 1. We find that 80 %–90 % of the total reactivity lies in the top 50 % of the parcels and 25 %–35 % in the top 10 %, supporting previous model-only studies that tropospheric chemistry is driven by a fraction of all the air. In other words, accurate simulation of the least reactive 50 % of the troposphere is unimportant for global budgets. Surprisingly, the probability densities of species and reactivities averaged on a model scale (100 km) differ only slightly from the 2 km ATom data, indicating that much of the heterogeneity in tropospheric chemistry can be captured with current global chemistry models. Comparing the ATom reactivities over the tropical oceans with climatological statistics from six global chemistry models, we find excellent agreement with the loss of O3 and CH4 but sharp disagreement with production of O3. The models sharply underestimate O3 production below 4 km in both Pacific and Atlantic basins, and this can be traced to lower NOx levels than observed. Attaching photochemical reactivities to measurements of chemical species allows for a richer, yet more constrained-to-what-matters, set of metrics for model evaluation.

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Marote, P., C. Matei, C. Sigala, and J. P. Deloume. "Influence of spectator ions on the reactivity of divalent metal salts in molten alkali metal nitrates." Materials Research Bulletin 40, no. 1 (January 2005): 1–11. http://dx.doi.org/10.1016/j.materresbull.2004.10.001.

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32

Savost'yanov, V. S., V. N. Vasilets, O. V. Ermakov, E. A. Sokolov, A. D. Pomogailo, D. A. Kritskaya, and A. N. Ponomarev. "Preparation and reactivity of metal-containing monomers. 21. Spontaneous polymerization of acrylamide coordinated to metal nitrates." Bulletin of the Russian Academy of Sciences Division of Chemical Science 41, no. 9 (September 1992): 1615–20. http://dx.doi.org/10.1007/bf00863582.

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33

Picquet-Varrault, Bénédicte, Ricardo Suarez-Bertoa, Marius Duncianu, Mathieu Cazaunau, Edouard Pangui, Marc David, and Jean-François Doussin. "Photolysis and oxidation by OH radicals of two carbonyl nitrates: 4-nitrooxy-2-butanone and 5-nitrooxy-2-pentanone." Atmospheric Chemistry and Physics 20, no. 1 (January 14, 2020): 487–98. http://dx.doi.org/10.5194/acp-20-487-2020.

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Abstract. Multifunctional organic nitrates, including carbonyl nitrates, are important species formed in NOx-rich atmospheres by the degradation of volatile organic compounds (VOCs). These compounds have been shown to play a key role in the transport of reactive nitrogen and, consequently, in the ozone budget; they are also known to be important components of the total organic aerosol. However, very little is known about their reactivity in both the gas and condensed phases. Following a previous study that we published on the gas-phase reactivity of α-nitrooxy ketones, the photolysis and reaction with OH radicals of 4-nitrooxy-2-butanone and 5-nitrooxy-2-pentanone (which are a β-nitrooxy ketone and γ-nitrooxy ketone, respectively) were investigated for the first time in simulation chambers. The photolysis frequencies were directly measured in the CESAM chamber, which is equipped with a very realistic irradiation system. The jnitrate/jNO2 ratios were found to be (5.9±0.9)×10-3 for 4-nitrooxy-2-butanone and (3.2±0.9)×10-3 for 5-nitrooxy-2-pentanone under our experimental conditions. From these results, it was estimated that ambient photolysis frequencies calculated for typical tropospheric irradiation conditions corresponding to the 1 July at noon at 40∘ N (overhead ozone column of 300 and albedo of 0.1) are (6.1±0.9)×10-5 s−1 and (3.3±0.9)×10-5 s−1 for 4-nitrooxy-2-butanone and 5-nitrooxy-2-pentanone, respectively. These results demonstrate that photolysis is a very efficient sink for these compounds with atmospheric lifetimes of few hours. They also suggest that, similarly to α-nitrooxy ketones, β-nitrooxy ketones have enhanced UV absorption cross sections and quantum yields equal to or close to unity and that γ-nitrooxy ketones have a lower enhancement of cross sections, which can easily be explained by the larger distance between the two chromophore groups. Thanks to a product study, the branching ratio between the two possible photodissociation pathways is also proposed. Rate constants for the reaction with OH radicals were found to be (2.9±1.0)×10-12 and (3.3±0.9)×10-12 cm3 molecule−1 s−1, respectively. These experimental data are in good agreement with rate constants estimated by the structure–activity relationship (SAR) of Kwok and Atkinson (1995) when using the parametrization proposed by Suarez-Bertoa et al. (2012) for carbonyl nitrates. Comparison with photolysis rates suggests that the OH-initiated oxidation of carbonyl nitrates is a less efficient sink than photodissociation but is not negligible in polluted areas.

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Pérez-Torres, Israel, Mohammed El Hafidi, Oscar Infante, and Guadalupe Baños. "Effects of sex hormone levels on aortic vascular reactivity and variables associated with the metabolic syndrome in sucrose-fed female rats." Canadian Journal of Physiology and Pharmacology 86, no. 1-2 (January 2008): 25–35. http://dx.doi.org/10.1139/y07-113.

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We studied the effect of varying levels of sex hormones, induced by ovariectomy and administration of testosterone or estradiol, on aortic reactivity in female rats with metabolic syndrome (MS) induced by a sucrose diet. Vasoreactivity of aortic rings, blood pressure, intra-abdominal fat, serum triglycerides, nitrates and nitrites, and TBARS were evaluated. Intact MS and ovariectomized MS had higher BP than intact control (C) and ovariectomized C, respectively; estradiol administration decreased BP in ovariectomized MS but not in ovariectomized C. Triglycerides and fat were both higher in MS. Triglycerides were not modified by surgery or hormone treatment, but ovariectomy increased fat. When ovariectomy was combined with hormones, however, fat was reduced to the level of intact rats. Ovariectomy decreased, but hormones increased, serum nitrates and nitrites. Vasoconstriction was larger in intact MS and ovariectomized MS + testosterone aortas than in intact C and ovariectomized C + testosterone, respectively. Vasodilation was reduced in intact MS and ovariectomized MS + testosterone compared with intact C, ovariectomized C + testosterone, ovariectomized MS, and ovariectomized MS + estradiol. The results suggest endothelial dysfunction in intact MS and ovariectomized MS + testosterone, but protection by ovariectomy + estradiol in MS due to hormones. Indomethacin reduced all contractions, but the effect was greater in estradiol-treated rats. l-NAME increased contractility, more in the ovariectomized C and MS groups and less in the estradiol-treated groups.

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Whitehouse, L. E., A. S. Tomlin, and M. J. Pilling. "Systematic reduction of complex tropospheric chemical mechanisms, Part II: Lumping using a time-scale based approach." Atmospheric Chemistry and Physics 4, no. 7 (October 5, 2004): 2057–81. http://dx.doi.org/10.5194/acp-4-2057-2004.

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Abstract. This paper presents a formal method of species lumping that can be applied automatically to intermediate compounds within detailed and complex tropospheric chemical reaction schemes. The method is based on grouping species with reference to their chemical lifetimes and reactivity structures. A method for determining the forward and reverse transformations between individual and lumped compounds is developed. Preliminary application to the Leeds Master Chemical Mechanism (MCMv2.0) has led to the removal of 734 species and 1777 reactions from the scheme, with minimal degradation of accuracy across a wide range of test trajectories relevant to polluted tropospheric conditions. The lumped groups are seen to relate to groups of peroxy acyl nitrates, nitrates, carbonates, oxepins, substituted phenols, oxeacids and peracids with similar lifetimes and reaction rates with OH. In combination with other reduction techniques, such as sensitivity analysis and the application of the quasi-steady state approximation (QSSA), a reduced mechanism has been developed that contains 35% of the number of species and 40% of the number of reactions compared to the full mechanism. This has led to a speed up of a factor of 8 in terms of computer calculation time within box model simulations.

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Whitehouse, L. E., A. S. Tomlin, and M. J. Pilling. "Systematic lumping of complex tropospheric chemical mechanisms using a time-scale based approach." Atmospheric Chemistry and Physics Discussions 4, no. 4 (July 8, 2004): 3785–834. http://dx.doi.org/10.5194/acpd-4-3785-2004.

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Abstract. This paper presents a formal method of species lumping that can be applied automatically to intermediate compounds within detailed and complex tropospheric chemical reaction schemes. The method is based on grouping species with reference to their chemical lifetimes and reactivity structures. A method for determining the forward and reverse transformations between individual and lumped compounds is developed. Preliminary application to the Leeds Master Chemical Mechanism (MCMv2.0) has led to the removal of 734 species and 1777 reactions from the scheme, with minimal degradation of accuracy across a wide range of test trajectories relevant to polluted tropospheric conditions. The lumped groups are seen to relate to groups of peroxy acyl nitrates, nitrates, carbonates, oxepins, substituted phenols, oxeacids and peracids with similar lifetimes and reaction rates with OH. In combination with other reduction techniques, such as sensitivity analysis and the application of the quasi-steady state approximation (QSSA), a reduced mechanism has been developed that contains 35% of the number of species and 40% of the number of reactions compared to the full mechanism. This has led to a speed up of a factor of 8 in terms of computer calculation time within box model simulations.

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Theologides, C. P., G. G. Olympiou, P. G. Savva, N. A. Pantelidou, B. K. Constantinou, V. K. Chatziiona, L. Y. Valanidou, C. T. Piskopianou, and C. N. Costa. "Novel catalytic and mechanistic studies on wastewater denitrification with hydrogen." Water Science and Technology 69, no. 3 (December 4, 2013): 680–86. http://dx.doi.org/10.2166/wst.2013.781.

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The present work reports up-to-date information regarding the reaction mechanism of the catalytic hydrogenation of nitrates in water media. In the present mechanistic study, an attempt is made, for the first time, to elucidate the crucial role of several catalysts and reaction parameters in the mechanism of the NO3−/H2 reaction. Steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with ex situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed on supported Pd-Cu catalysts for the NO3−/H2 and NO3−/H2/O2 reactions. The latter experiments revealed that the formation and surface coverage of various adsorbed active intermediate N-species on the support or Pd/Cu metal surface is significantly favored in the presence of TiO2 in the support mixture and in the presence of oxygen in the reaction's gaseous feed stream. The differences in the reactivity of these adsorbed N-species, found in the present work, adequately explain the large effect of the chemical composition of the support and the gas feed composition on catalyst behaviour (activity and selectivity). The present study leads to solid mechanistic evidence concerning the presence of a hydrogen spillover process from the metal to the support. Moreover, this study shows that Cu clusters are active sites for the reduction of nitrates to nitrites.

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Olabe, José. "Coordination Chemistry of Nitric Oxide and Biological Signaling." Science Reviews - from the end of the world 2, no. 1 (December 18, 2020): 64–99. http://dx.doi.org/10.52712/sciencereviews.v2i1.33.

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Nitric Oxide (NO) is a key intermediate in the nitrogen redox cycles that operate in soils, water and biological fluids, affording reversible interconversions between nitrates to ammonia and vice-versa. The discovery of its biosynthesis in mammals for signaling purposes generated a research explosion on the ongoing chemistry occurring in specific cellular compartments, centered on NO reactivity toward O2, thiols, amines, and transition metals, as well as derivatives thereof. The present review deals with the coordination chemistry of NO toward selected iron and ruthenium centers. We place specific attention to the three redox states of the nitrosyl group: NO+, NO and NO–/HNO, describing changes in structure and reactivity as coordination takes place. Noteworthy are the results with the most reduced nitroxyl-species that allow establishing the changes in the measurable pKa values for the HNO-bound complexes, also revealing the abrupt decrease in reducing power and trans-releasing abilities of the protonated species over the unprotonated ones, NO–. Comparative results using non-heme and heme proteins and models prove useful for suggesting further improvements in the current research status of complex enzymatic behavior.

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Ouahdi, N., S. Guillemet, J. J. Demai, B. Durand, L. Er Rakho, R. Moussa, and A. Samdi. "Investigation of the reactivity of AlCl3 and CoCl2 toward molten alkali-metal nitrates in order to synthesize CoAl2O4." Materials Letters 59, no. 2-3 (February 2005): 334–40. http://dx.doi.org/10.1016/j.matlet.2004.10.013.

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Sadykov, V. A., E. A. Paukshtis, S. A. Beloshapkin, G. M. Alikina, S. A. Veniaminov, E. V. Netyaga, R. V. Bunina, et al. "Reactivity and transformation routes of surface nitrates in the reaction of NOx reduction by C3H8 over cation-exchanged zeolites." Reaction Kinetics and Catalysis Letters 65, no. 1 (September 1998): 113–19. http://dx.doi.org/10.1007/bf02475324.

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Baer, H. P., R. Vriend, and A. Murji. "Interaction of 2′,3′-di-O-nitro-5′-(N-ethylcarboxamido)adenosine with adenosine receptors in intestinal smooth muscle." Canadian Journal of Physiology and Pharmacology 63, no. 5 (May 1, 1985): 449–52. http://dx.doi.org/10.1139/y85-078.

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The adenosine derivative, 2′3′-di-O-nitro-(5′-N-ethylcarboxamido)adenosine (DINECA), caused relaxation in several isolated smooth muscle preparations including guinea pig taenia caeci, beef coronary arteries, and rabbit small intestine. In rabbit small intestine the response profile of DINECA action differed from that of established adenosine receptor agonists and, in contrast with the latter, its relaxant effect was only partially reversed by the antagonist 8-p-sulfophenyltheophylline. Concentration–response curves to 5′-(N-ethylcarboxamido)adenosine (NECA), but not those to DINECA, were significantly shifted to the right by 100 μM of 8-sulfophenyltheophylline. Tissues exposed previously to DINECA became refractory to adenosine, an effect not observed with tissues exposed to NECA, suggesting that DINECA became bound to adenosine receptors. Adenylate cyclase from neuroblastoma cells, containing Ra-type adenosine receptors, was stimulated by 2-chloroadenosine and NECA but not by DINECA. The results suggest that most of the smooth muscle relaxant actions of DINECA are not due to interaction with adenosine receptors but are probably due to its function as a nitrate. However, DINECA appears to interact with adenosine receptors, causing long lasting inhibition of adenosine action in rabbit intestine. Such actions may contribute to the overall response to DINECA application in vivo, although lowering of blood pressure due to the high reactivity of the vasculature to nitrates may be the initial and major effect.

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Pospíšil, Milan, and Jan Topinka. "The effect of origin and physico-chemical properties on the kinetics of reduction of mixed NiO-Fe2O3 oxides with hydrogen." Collection of Czechoslovak Chemical Communications 51, no. 10 (1986): 2098–108. http://dx.doi.org/10.1135/cccc19862098.

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We investigated the effect of origin and some physico-chemical parameters on the kinetics of reduction with hydrogen of two series of mixed NiO-Fe2O3 oxides differing by their composition, the character of their precursors (mixed crystalline nitrates and coprecipitated hydroxides) and their decomposition temperature.This effect manifested itself by different magnitudes of specific surfaces of the mixed oxides and coherent regions of present phases as well as by different oxidizing abilities of the surface and differences in morphology and phase composition of corresponding samples in both series investigated. Nonlinear or nonmonotonous composition dependences of physico-chemical parameters investigated point to a mutual influence of individual components, which is also a function of the system origin and which modifies its reactivity during its reduction with hydrogen. The kinetics of the reduction was studied thermogravimetrically at 320-410 °C. The reduction of oxides of the hydroxide origin is catalytically accelerated by primarily reduced nickel, whereas in corresponding samples of the nitrate series, the total NiO is bound to the spinel phase and the reduction is delayed. Experimental IR spectra, the effect of preliminary annealing and DTA of the mixed oxides point to an inhibitory effect of water, which is constitutionally bound in trace admixtures of the goethite phase, on the kinetics of reduction of samples in the hydroxide series.

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Gadalla, Ahmed M., and Hsuan-Fu Yu. "Preparation of fine, hollow, spherical NiFe2O4 powders." Journal of Materials Research 5, no. 12 (December 1990): 2923–27. http://dx.doi.org/10.1557/jmr.1990.2923.

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Aerosol droplets of a dilute aqueous solution of Ni(II) and Fe(III) nitrates were used to synthesize fine nickel ferrite powders by pyrolysis at temperatures ranging from 450 °C to 810 °C. The aerosol product was characterized by thermal analysis, x-ray diffraction, scanning electron microscopy, and BET surface area determination. At low temperature (480 °C), very active fine, hollow, noncrystalline spheres were formed. As the pyrolysis temperature increased, sintering occurred, larger particles with broader size distribution were obtained, and a higher degree of crystallinity of nickel ferrite was produced. The products at pyrolysis temperatures of 660 °C and above exhibited magnetic properties. The powders prepared from the aerosolization process at low temperatures had high reactivity and crystallized rapidly. The effect of the initial solution concentration was also studied, and dilute solutions produced spheres with fine size and narrow size distribution.

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Dewald, Patrick, Jonathan M. Liebmann, Nils Friedrich, Justin Shenolikar, Jan Schuladen, Franz Rohrer, David Reimer, et al. "Evolution of NO3 reactivity during the oxidation of isoprene." Atmospheric Chemistry and Physics 20, no. 17 (September 8, 2020): 10459–75. http://dx.doi.org/10.5194/acp-20-10459-2020.

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Abstract. In a series of experiments in an atmospheric simulation chamber (SAPHIR,1 Forschungszentrum Jülich, Germany), NO3 reactivity (kNO3) resulting from the reaction of NO3 with isoprene and stable trace gases formed as products was measured directly using a flow tube reactor coupled to a cavity ring-down spectrometer (FT-CRDS). The experiments were carried out in both dry and humid air with variation of the initial mixing ratios of ozone (50–100 ppbv), isoprene (3–22 ppbv) and NO2 (5–30 ppbv). kNO3 was in excellent agreement with values calculated from the isoprene mixing ratio and the rate coefficient for the reaction of NO3 with isoprene. This result serves to confirm that the FT-CRDS returns accurate values of kNO3 even at elevated NO2 concentrations and to show that reactions of NO3 with stable reaction products like non-radical organic nitrates do not contribute significantly to NO3 reactivity during the oxidation of isoprene. A comparison of kNO3 with NO3 reactivities calculated from NO3 mixing ratios and NO3 production rates suggests that organic peroxy radicals and HO2 account for ∼50 % of NO3 losses. This contradicts predictions based on numerical simulations using the Master Chemical Mechanism (MCM version 3.3.1) unless the rate coefficient for reaction between NO3 and isoprene-derived RO2 is roughly doubled to ∼5×10-12 cm3 molecule−1 s−1.

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Matta, Anthony, Frederic Bouisset, Thibault Lhermusier, Fran Campelo-Parada, Meyer Elbaz, Didier Carrié, and Jerome Roncalli. "Coronary Artery Spasm: New Insights." Journal of Interventional Cardiology 2020 (May 15, 2020): 1–10. http://dx.doi.org/10.1155/2020/5894586.

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Coronary artery spasm (CAS) defined by a severe reversible diffuse or focal vasoconstriction is the most common diagnosis among INOCA (ischemia with no obstructive coronary artery disease) patients irrespective to racial, genetic, and geographic variations. However, the prevalence of CAS tends to decrease in correlation with the increasing use of medicines such as calcium channel blockers, angiotensin converting enzyme inhibitor, and statins, the controlling management of atherosclerotic risk factors, and the decreased habitude to perform a functional reactivity test in highly active cardiac catheterization centers. A wide spectrum of clinical manifestations from silent disease to sudden cardiac death was attributed to this complex entity with unclear pathophysiology. Multiple mechanisms such as the autonomic nervous system, endothelial dysfunction, chronic inflammation, oxidative stress, and smooth muscle hypercontractility are involved. Regardless of the limited benefits proffered by the newly emerged cardiac imaging modalities, the provocative test remains the cornerstone diagnostic tool for CAS. It allows to reproduce CAS and to evaluate reactivity to nitrates. Different invasive and noninvasive therapeutic approaches are approved for the management of CAS. Long-acting nondihydropyridine calcium channel blockers are recommended for first line therapy. Invasive strategies such as PCI (percutaneous coronary intervention) and CABG (coronary artery bypass graft) have shown benefits in CAS with significant atherosclerotic lesions. Combination therapies are proposed for refractory cases.

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Culic, Carina, Alina Elena Parvu, Sandu Florin Alb, Camelia Alb, and Angela Pop. "EFFECT OF CIMETIDINE ON NITRO-OXIDATIVE STRESS IN A RAT MODEL OF PERIODONTITIS." Medicine and Pharmacy Reports 87, no. 3 (August 5, 2014): 177–81. http://dx.doi.org/10.15386/cjmed-273.

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Background and aims. Periodontitis is a chronic inflammation that involves nitro-oxidative stress with damaging periodontal structural effects. We aimed to evaluate the consequences of low-dose cimetidine on nitro-oxidative stress in periodontitis. Methods. A rat model of ligature-induced periodontitis was used. After two weeks, the periodontitis groups were treated with cimetidine, aminoguanidine, N-nitro-L-arginine methyl ester and trolox for one week. On day 21, blood was drawn and the serum analyzed for measurement of total nitrites and nitrates, total oxidative status, total antioxidant response, and oxidative stress index. Results. Cimetidine had an inhibitory effect on the synthesis of nitric oxide (p=0.001), total oxidative status (p=0.01) and oxidative stress index (p=0.01). Total antioxidant reactivity was increased by cimetidine (p=0.01). The effects of cimetidine were almost like those of aminoguanidine, NG-nitro-L-arginine methyl ester, and trolox. Conclusions. Low-dose cimetidine can be used as adjunctive host modulatory therapy in chronic periodontitis because it reduces nitro-oxidative stress.

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Wang, Yarong, Toshiyuki Mori, Ji-Guang Li, Takayasu Ikegami, and Yoshiyuki Yajima. "Low-temperature preparation of dense 10 mol%-Y2O3-doped CeO2 ceramics using powders synthesized via carbonate coprecipitation." Journal of Materials Research 18, no. 5 (May 2003): 1239–46. http://dx.doi.org/10.1557/jmr.2003.0170.

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A carbonate coprecipitation method was used for the facile synthesis of highly reactive 10 mol%-Y2O3-doped CeO2 (20YDC) nanopowders, employing nitrates as the starting salts and ammonium hydrogen carbonate (AHC) as the precipitant. The AHC/RE3+ (RE = Ce + Y) molar ratio (R) and the reaction temperature (T) significantly affect the final yield and precursor properties, including chemical composition and particle morphology. Suitable processing conditions are T = 60 °C and R = 2.5 to 10, under which precipitation is complete, and the resultant precursors show ultrafine particle size, spherical particle shape, and good dispersion. The thus-processed precursors are basic carbonates with an approximate formula of Ce0.8Y0.2(OH)CO3 · 2H2O, which directly yield oxide solid solutions upon thermal decomposition at a very low temperature of approximately 400 °C. The 20YDC solid-solution powders calcined at 700 °C show excellent reactivity and were densified to >99% of theoretical via pressureless sintering at a very low temperature of 950 °C for 6 h.

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Albalawi, Abdulmajeed F., Hamoud T. Alotaibi, Razan K. Alharbi, Abdulrahman A. Alghamdi, Ali A. Alzahrani, Jwael A. Alhamoud, Saleem A. Alzahrani, et al. "Modifiable risk factors of vasospastic angina: a systematic literature review." International Journal Of Community Medicine And Public Health 8, no. 3 (February 24, 2021): 1481. http://dx.doi.org/10.18203/2394-6040.ijcmph20210848.

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Vasospastic angina is caused by transient coronary spasms unrelated to exertion, which may even occur at rest (classically at night) and promptly responds to short acting nitrates. It is thought to be caused by inherent generalised hyper reactivity of the smooth muscle cells of epicardial vessels to various stimuli. Being comparatively less studied, the risk factors for VSA vary considerably from obstructive or atherosclerotic cardiac disease. However, coronary vasospasm can occur in non stenosed arteries, atherosclerotic arteries as well as sub critically stenosed arteries which can result in significant overlap between the risk factors and underlying pathophysiology. 1-14% of AMI can be caused by non-obstructive, or ‘functional’ coronary artery disorders like vasospastic angina but VSA continues to be underdiagnosed and less well understood than obstructive coronary artery disorders. This prompted us to study the existing literature for modifiable risk factors of coronary artery vasospasm so that an emphasis can be made on proper lifestyle modifications and avoidance of vasospastic agents in susceptible individuals. Smoking proved to be the most important risk factor whereas recreational drugs and drugs used for treatment of certain medical disorders have also been shown to associate with coronary vasospasm. Medical personnel, therefore, need to be more vigilant in history taking as well as investigating cardiac chest pain in which traditional investigations end up being normal so that an early diagnosis of vasospastic angina can be made and appropriate steps taken to improve the quality of life of patients.

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REMADI, J. P., B. COLAS, H. MASSON, M. SLAMA, and M. ANDRÉJACK. "Effect of linsidomine on the human radial artery." Clinical Science 103, no. 1 (June 5, 2002): 1–6. http://dx.doi.org/10.1042/cs1030001.

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The response of the human radial artery to a direct NO donor, linsidomine or 3-morpholino-sydnonimine (Sin 1), in the therapeutic management of peri-operative spasm may increase the patency rates of these grafts in the short, medium and long term. Evaluation of the effects of Sin 1 on the human radial artery is of even greater interest as it has not been published previously. Ninety-six human radial artery rings were studied with two protocols. Rings were mounted in an isolated organ bath between two stainless steel metallic rods connected to stress gauges. Protocol 1 studied the vasorelaxant effect of Sin 1 and nitroglycerin (TNT). Protocol 2 studied the reactivity of the radial artery to the vasoconstrictor agents arginine vasopressin (AVP) and angiotensin II (ANG II). The vasorelaxant effect of Sin 1 on the human radial artery was comparable with that of TNT, but with no tolerance effect. After Sin 1 pre-incubation, the vasoconstrictor effect of ANG II was abolished, whereas AVP induced maximum vasoconstriction similar to that of the control (not statistically significant), but with a shift in the EC50 to higher concentrations, EC50 = 15±20nM. Sin 1 vasorelaxation of rings precontracted by ANG II was maximal, whereas after contraction by AVP, relaxation remained less than 70%; Sin 1 is a potent vasorelaxant on the human radial artery, which does not exhibit cross-tolerance with nitrates. This compound may be used pre- or post-operatively, and would undoubtedly be of benefit in the peri-operative preparation bath.

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Rosevear, J., and JFK Wilshire. "A comparison of the reactions of some ethyl N-Arylcarbamates with those of the corresponding acetanilides. I. Nitration." Australian Journal of Chemistry 38, no. 5 (1985): 723. http://dx.doi.org/10.1071/ch9850723.

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The reactions of some ethyl N- arylcarbamates and of the corresponding acetanilides towards 1 equiv. of sodium nitrate in concentrated sulfuric acid at 0-5° have been compared with one another and have been found to exhibit significant differences. Except in the case of the unsubstituted analogues, nitration of the carbamates was found to occur significantly more quickly than that of the acetanilides as shown by ( i ) a representative competitive nitration, and (ii) the fact the carbamates containing a nitro group are nitrated smoothly whereas the corresponding nitroacetanilides are slow to react. On the basis of competitive reactions, it is suggested that this difference in reactivity is due to steric factors.

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Journal articles on the topic 'Nitrates – Reactivity'

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