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Journal articles on the topic 'Resonance and Steric Effects'

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Published: 5 June 2025

Last updated: 1 August 2025

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1

KULANDAIVELU, KARUNAKARAN, GURUMURTHY RAJAGOPALA, and PITCHAIMUTHU ELANGO KUPPANNAGOUNDER. "Steric and Resonance Effects on the Kinetics of Oxidation of Organic Sulfides by Quinolinium Fluorochromate." Journal of Indian Chemical Society Vol. 75, May 1998 (1998): 297–99. https://doi.org/10.5281/zenodo.5927158.

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Department of Chemistry, Annamalai University, Annamalainagar-608 002 Department of Chemistry, Gandhigram Rural Institute, Gandhigram-624 302 <em>Manuscript received 25 March 1996, revised 20 August 1997, accepted 30 September 1997</em> Kinetics of oxidation of dialkyl, alkyl phenyl and benzal methyl phenyl sulfides to their sulfoxides by quinolinium fluorochromate (QFC) have been followed in aqueous acetic acid. The order of the reaction is found to be one each with respect to QFC, H<sub>3</sub>O<sup>+</sup> and the sulfide. Increase in the dielectric constant of the medium decreases the rate

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2

V., BALIAH, and UMA M. "Influence of ortho-Substituents on the + M and - M Effects of SCH3 Group in Aryl Methyl Sulphides. A Study by Dipole Moments." Journal of Indian Chemical Society Vol. 69, Jan 1992 (1992): 21–23. https://doi.org/10.5281/zenodo.5991471.

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Department of Chemistry, Annamalai University, Annsmalainagat-008 002 <em>Manuscript received 10 April 1991, revised 12 September 1991, accepted 7 January 1992</em> The dipole moments of twelve aryl methyl sulphides have been determined. The effect of mono-<em>ortho</em>- and di-<em>ortho-</em>substitution on the +M and -M effects of the SCH, group has been analysed by a comparison of the observed and calculated dipole moments of aryl methyl sulphides A single substituent ortho to SCH, group is found to cause a slight steric enhancement of both the donor and acceptor resonances of SCH, Di

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3

Císařová, Ivana, Jaroslav Podlaha, Stanislav Böhm, and Otto Exner. "Steric Effects and Steric Inhibition of Resonance in Benzene Derivatives: 2,3-Dimethylbenzoic Acid." Collection of Czechoslovak Chemical Communications 65, no. 2 (2000): 216–26. http://dx.doi.org/10.1135/cccc20000216.

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Structure of 2,3-dimethylbenzoic acid was determined both by single-crystal X-ray diffraction and by ab initio calculation at an RHF/6-31+G** level. Comparing with a previous X-ray analysis of another crystal modification of the same compound, it was possible to estimate the effect of crystal forces on the conformation. The isolated molecule is not planar as deduced previously, mainly from IR spectra, but the carboxyl group is twisted out of the ring plane by a torsion angle ϕ = 12°. In the crystal, the molecule is more flat and ϕ is reduced to 7 and 1° in the two modifications, respectively.

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4

A., Abdul Jameel, and Krishna Pillay M. "Nature of ortho effect in the oxidation of ortho-substituted-benzaldehydes with pyridinium chlorochromate." Journal of Indian Chemical Society Vol. 76, Feb 1999 (1999): 101–3. https://doi.org/10.5281/zenodo.5852439.

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Department of Chemistry, Jamal Mohamed College, Tiruchirappalli-620 020, India Department of Chemistry, Bharathidasan University, Tiruchirappalli-620 024, India <em>Manuscript received 10 February 1998, revised 25 August 1998, accepted 9 September 1998</em> Rate constants for the oxidation reaction of ortlzo-substituted benzaldehydes with pyridinium chlorochromate are correlated with equations log <em>k</em><sub>2</sub>= ασ<sub>1</sub> + β σ<sub>k</sub> + <sup>\(\Psi\)</sup>  v +<em> h</em> log <em>k</em><sub>2</sub>= ασ<sub>1</sub> + β &s

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5

Ploom, Anu, Ants Tuulmets, and Jaak Järv. "Structure-reactivity relationships in organosilicon chemistry revisited." Open Chemistry 9, no. 5 (2011): 910–16. http://dx.doi.org/10.2478/s11532-011-0075-x.

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AbstractAvailable quantitative data of the reactivity of organosilicon compounds were subjected to correlation analysis. As an alternative to the carbon chemistry values, the scale of steric constants E S (Si) can be used for organosilicon compounds and the inductive effect is best expressed by two terms, involving the parameter of electronegativity of substituents. Alkyl substituents contribute to the reactivity exclusively through their steric effects, steric and polar effects in silicon compounds are additive and the resonance effect is insignificant. The correlation analysis can be employe

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6

Böhm, Stanislav, and Otto Exner. "Steric effects and steric inhibition of resonance: structure and ionization of 2-tert-butylbenzoic acid." New Journal of Chemistry 25, no. 2 (2001): 250–54. http://dx.doi.org/10.1039/b005691j.

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7

Fiedler, Pavel, Jiří Kulhánek, Michèle Decouzon, Jean-François Gal, Pierre-Charles Maria, and Otto Exner. "Steric Effects and Steric Inhibition of Resonance in Isopropylbenzoic Acids in the Gas Phase and in Solution." Collection of Czechoslovak Chemical Communications 64, no. 9 (1999): 1433–47. http://dx.doi.org/10.1135/cccc19991433.

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The substituent effects of the isopropyl group in 2-, 3- and 4-isopropylbenzoic acids were investigated on the enthalpies of formation, gas-phase acidities, acidities in methanol and in dimethyl sulfoxide, and on the IR spectra in tetrachloromethane. Particular attention was given to the influence of variable conformation on the observed steric effect. In contrast to 2-tert-butylbenzoic acid and similarly to 2-methylbenzoic acid, 2-isopropylbenzoic acid exists in two planar conformations in equilibrium. Due to this conformational freedom, the steric effects of the isopropyl group on the confor

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8

Kulhánek, Jiří, Michèle Decouzon, Jean-François Gal, et al. "Steric Effects and Steric Hindrance to Resonance intert-Butylbenzoic Acids in the Gas Phase and in Solution." European Journal of Organic Chemistry 1999, no. 7 (1999): 1589–94. http://dx.doi.org/10.1002/(sici)1099-0690(199907)1999:7<1589::aid-ejoc1589>3.0.co;2-s.

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9

Jovanovic, Bratislav, Fathi Assaleh, and Aleksandar Marinkovic. "Kinetics of the reaction of 5-substituted orotic acids with diazodiphenylmethane." Journal of the Serbian Chemical Society 69, no. 11 (2004): 949–53. http://dx.doi.org/10.2298/jsc0411949j.

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Rate konstants for the reaction of eight 5-substituted orotic acids with diazodiphenylmethane (DDM) in dimethylformamide (DMF) were determined at 30 ?C by the known spectrophotometricmethod. The determined rate constants were correlated with the equations: logk2 = ??1+??R+h logk2 = ??1+??R+??+h to detect the presence and investigate the influence of both electrical and steric substituent effects. The obtained results show that the electrical effect (the localized ? field and delocalized ? resonance) is predominant and that the steric effect, althought present, is releatively small in this reac

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10

Yamagami, C., N. Takao та Y. Takeuchi. "15N Nuclear Magnetic-Resonance Spectra of ortho-Substituted Phenylacetanilides: The Origin of γ-syn Effects". Australian Journal of Chemistry 42, № 4 (1989): 463. http://dx.doi.org/10.1071/ch9890463.

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The 15N chemical shifts of X α and Y α, i.e., the nuclei through which the side chains, X and Y, respectively, of o-substituted phenylacetanilides (2a) are bonded to the aromatic ring were determined. There was observed a uniform upfield shift (γsyn effect). In order to explore the origin of the γ effect, other o-disubstitutes benzenes (2b-d) were also examined. The values of D, defined as the difference between γ α substituent chemical shifts of the ortho (2) and para (3) series of compounds, and considered as a measure of the γ-syn effect, were correlated with various electronic and steric s

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11

Boykin, David W., Alfons L. Baumstark, Margaret M. Kayser, and Chantal M. Soucy. "17O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides." Canadian Journal of Chemistry 65, no. 6 (1987): 1214–17. http://dx.doi.org/10.1139/v87-204.

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17O chemical shift data (natural abundance) for 3-substituted phthalic anhydrides and 4- and 7-substituted phthalides in acetonitrile at 75 °C are reported. Steric interactions of substituents ortho to the carbonyl groups result in deshielding effects (9–22 ppm) relative to parent compounds regardless of the electronic character of the substituents. Factors contributing to the deshielding effects are discussed. The relationship between 17O chemical shifts and regiochemistry of the phthalic anhydrides is discussed.

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12

Bolton, R., RE Burley, and NJ Williams. "Stabilities of Carbonium-Ions. IV. Steric Effects in the Solvolysis of Substituted Diphenylmethyl Chlorides." Australian Journal of Chemistry 39, no. 4 (1986): 625. http://dx.doi.org/10.1071/ch9860625.

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The replacement of ortho-hydrogen atoms by methyl groups in diphenylmethyl chloride has three distinguishable results upon the rate of solvolysis . Firstly, the alkyl groupactivates by its electronic effect; secondly, steric interactions diminish all observed substituent effects regardless of the position of the substituent in the aryl system; and thirdly, steric acceleration of the solvolysis can be seen in the rate of reaction of bis (2,6-dimethylphenyl)methyl chloride. The ortho-methyl substituents inhibit the formation of the planar transition state necessary to allow the greatest resonanc

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13

Yamagami, C., N. Takao, and Y. Takeuchi. "Effects of Substituents on the Barriers to Rotation in Phenyl and Benzyl Carbamates." Australian Journal of Chemistry 39, no. 3 (1986): 457. http://dx.doi.org/10.1071/ch9860457.

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The free energy of activation for rotation about the C-N bond (ΔG‡Tc) in substituted phenyl and benzyl N,N- dimethylcarbamates was determined by the 13C dynamic n.m.r. method. The ΔG‡Tc value depended linearly on Hammett's σ with positive p. We have separated the substituent effects into inductive and resonance effects by using dual substituent parameter ( d.s.p .) analysis, and found that the resonance effect is more important than the inductive effect for para derivatives, and vice versa for meta derivatives. General trends of electronic substituent effects on barriers to rotation in carbama

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14

Grossert, J. Stuart, H. Ranjith W. Dharmaratne, T. Stanley Cameron та Beverly R. Vincent. "Steric effects in the diastereoselective reduction of β-ketosulfones". Canadian Journal of Chemistry 66, № 11 (1988): 2860–69. http://dx.doi.org/10.1139/v88-443.

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The stereochemical course of the reduction of ketones adjacent to a chiral center normally shows some diastereoselectivity (described by Cram's rule), the degree of which is dependent on the structure of the ketone and on the reaction conditions; the selectivity in acyclic species is often not very great. In this paper, we describe the sodium borohydride reduction of four acyclic β-ketosulfones, containing a chiral center at the α position, in which the products are formed with high diastereoselectivity. Reasons for this selectivity became apparent when we were able to show that these ketosulf

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15

Nummert, Vilve, Mare Piirsalu, Signe Vahur, Oksana Travnikova, and Ilmar A. Koppel. "Kinetic study of hydrolysis of benzoates. part xxvii. ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous Bu4NBr." Collection of Czechoslovak Chemical Communications 74, no. 1 (2009): 29–42. http://dx.doi.org/10.1135/cccc2008019.

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The second-order rate constants k (in dm3 mol–1 s–1) for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, have been measured spectrophotometrically in aqueous 0.5 and 2.25 M Bu4NBr at 25 °C. The substituent effects for para and meta derivatives were described using the Hammett relationship. For the ortho derivatives the Charton equation was used. For ortho-substituted esters two steric scales were involved: the EsB and the Charton steric (υ) constants. When going from pure water to aqueous 0.5 and 2.25 M Bu4NBr, the meta and para polar ef

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16

Nummert, Vilve, Vahur Mäemets, Mare Piirsalu, Signe Vahur, and Ilmar A. Koppel. "17O NMR study of ortho and alkyl substituent effects in substituted phenyl and alkyl esters of benzoic acids." Collection of Czechoslovak Chemical Communications 76, no. 12 (2011): 1737–63. http://dx.doi.org/10.1135/cccc2011100.

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17O NMR spectra for 44 ortho-, meta- and para-substituted phenyl and alkyl benzoates (C6H5CO2C6H4-X, C6H5CO2R) at natural abundance in acetonitrile were recorded. Substituent effects on the 17O NMR chemical shifts, δ(17O), of the carbonyl oxygen and the single-bonded phenoxy (OPh) and alkoxy (OR) oxygens have been studied. The δ(17O) values of the carbonyl oxygen for para derivatives showed a good correlation with the σ° constants. The δ(17O) values of carbonyl oxygen for ortho derivatives were found to be described well with the Charton equation containing the inductive, σI, resonance, σ°R, a

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17

M., KRIHNA PILLAY, and PALANIVELU S. "Steric Enhancement of Resonance - Evidence from Kinetic Study on some Acetophenones." Journal of Indian Chemical Society Vol. 63, Dec 1986 (1986): 1055–59. https://doi.org/10.5281/zenodo.6277471.

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Department of Chemistry, Bharathidasan University, Tiruchirapalli-690 028 <em>Manuscript received 16 December 1986, revised 10 July 1986, accepted S September 1986</em> The kinetics of oxidation of some mono-, di- and tri-substituted acetophenones by alkaline hexacyanoferrate(III) in 50% (v/v) methanol—water mixture at constant ionic strength and at 20, 30 and 40° have been studied spectrophotometrically and the rate constants determined by least-squares analysis. Electron-withdrawing groups in the ring facilitate the oxidation of the acetyl function while electron-releasing groups r

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18

Zaitsev, Boris A. "Estimate of Hyperconjugation Strength in Alkylaromatics and Unsaturated Hydrocarbons Derived from Refractometric Data." Current Organic Chemistry 23, no. 23 (2020): 2598–613. http://dx.doi.org/10.2174/1385272823666191108100747.

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: A retrospective view of exaltation of refraction observed for many unsaturated and aromatic compounds demonstrates that this physical phenomenon is undeservedly considered only as a qualitative measure of conjugation. This mini-review discusses numerous papers by the author that have been published earlier in inaccessible periodicals and collections of scientific papers. Using a great number of illustrations, the author shows that this parameter can be successfully used for quantitative estimate of resonance effects in organic and polymer chemistry. The methods for derivation of strictly add

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19

Soderquist, Arlen, Julio C. Facelli, Walter J. Horton, and David M. Grant. "Low-Temperature 13C Magnetic Resonance. 9.Steric Effects for Methyl Chemical Shift Tensors in Methylcyclohexanes." Journal of the American Chemical Society 117, no. 32 (1995): 8441–46. http://dx.doi.org/10.1021/ja00137a020.

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20

Kulhánek, Jiří, Oldřich Pytela, and Antonín Lyčka. "Chemometrical Analysis of Substituent Effects. XIII. Comparison of Substituent Effects on Dissociation and Chemical Shift in 13C NMR Spectra of Mono- and Disubstituted Benzoic Acids." Collection of Czechoslovak Chemical Communications 65, no. 1 (2000): 106–16. http://dx.doi.org/10.1135/cccc20000106.

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The 13C chemical shifts have been measured of the carboxyl carbon atoms for all the 2-, 3-, and 4-substituted benzoic acids with H, CH3, CH3O, F, Cl, Br, I, and NO2 substituents, as well as for all 3,4-, 3,5-, and 2,6-disubstituted benzoic acids with combinations of CH3, CH3O, Cl (or Br), NO2 substituents and for symmetrically 2,6-disubstituted derivatives with Et, EtO, PrO, i-PrO, and BuO substituents. The chemical shifts of carboxylic group carbon atoms of the 3- and 4-substituted derivatives show correlation only with the substituent constants σI. For the 2-substituted derivatives was found

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21

Wang, Yulan, and Yangjie Wu. "Effects of ortho-Substituents in Protonolysis of Arylmercuric Chlorides with Hydrochloric Acid." Collection of Czechoslovak Chemical Communications 65, no. 1 (2000): 35–46. http://dx.doi.org/10.1135/cccc20000035.

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The kinetics of reaction of ortho-substituted phenylmercuric chlorides, 2-R-C6H4HgCl (R = H, CH3, CH3O, C2H5O, CF3, COOC2H5, Cl, Br, F, NO2), with hydrochloric acid in absolute ethanol in the presence of sodium iodide has been studied. The reaction is of the overall second order, first order with respect to each reactant. The rate constant determined at a fixed temperature decreases in the order of R: C2H5O > CH3O > CH3 > H > COOC2H5 > F > Cl > Br > CF3 > NO2. The role of inductive, resonance and field effects of the ortho-substituents, and the relation between steri

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22

Mazurkiewicz, Paul H., and Max L. Deinzer. "Steric Effects on Gas-Phase Negative Ion Resonances of Phthalates." Journal of the American Chemical Society 121, no. 14 (1999): 3421–27. http://dx.doi.org/10.1021/ja9828814.

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23

Hansen, Poul Erik, Fadhil S. Kamounah, Bahjat A. Saeed, Mark J. MacLachlan, and Jens Spanget-Larsen. "Intramolecular Hydrogen Bonds in Normal and Sterically Compressed o-Hydroxy Aromatic Aldehydes. Isotope Effects on Chemical Shifts and Hydrogen Bond Strength." Molecules 24, no. 24 (2019): 4533. http://dx.doi.org/10.3390/molecules24244533.

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A number of o-hydroxy aromatic aldehydes have been synthesized to illustrate the effect of steric compression and O···O distances on the intramolecular hydrogen bond and the hydrogen bond energies. Hydrogen bond energies have been calculated using the ‘hb and out’ method using either the MP2 method or the B3LYP functional with the basis set 6-311++G(d,p). However, several compounds cannot be treated this way. Hydrogen bond energies are also determined using electron densities at bond critical points and these results are in good agreement with the results of the ‘hb and out’ model. Two-bond de

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24

Haddad, Raid, Yi Lu, J. Martin E. Quirke, et al. "Steric bulkiness of pyrrole substituents and the out-of-plane deformations of porphyrins: nickel(II) octaisopropylporphyrin and its meso-nitro derivative." Journal of Porphyrins and Phthalocyanines 15, no. 07n08 (2011): 727–41. http://dx.doi.org/10.1142/s1088424611003707.

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Sterically bulky substituents at the β-carbons of the pyrrole rings of porphyrins are sufficient to cause large out-of-plane porphyrin distortions even in the absence of substituent groups at the meso carbons. It is well established that substituents at the meso-positions only or at both the β-pyrrole and the meso-positions are sufficiently bulky to result in large non-planar distortions of the macrocycle. However, no systematic studies of the effects of bulky β-pyrrole substituents alone have been reported. Herein, molecular simulations and X-ray crystallography of nickel(II) 2,3,7,8,12,13,17

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25

Liu, Hsing-Jang, and Eric N. C. Browne. "Diels–Alder reactions of 4,4-dimethyl-2-cyclohexenones. A direct route to the 4,4-dimethyl-1-decalones." Canadian Journal of Chemistry 65, no. 6 (1987): 1262–78. http://dx.doi.org/10.1139/v87-214.

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Diels–Alder additions to enones 1 and 2, synthetic equivalents of the synthon 3, were studied using a variety of hydrocarbon dienes. The two enones have been shown to be effective and synthetically useful dienophiles. Spectroscopic (especially 1H and 13C magnetic resonance) and chemical techniques were used to define unambiguously the full structures of the adducts. The structures of the various reaction products were used to draw qualitative conclusions about the nature of the transition states involved and the various electronic and steric effects that play a role in the mechanistic course o

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26

Nummert, Vilve, Mare Piirsalu, Vahur Mäemets, and Ilmar Koppel. "Kinetic Study of Hydrolysis of Benzoates. Part XXV. Ortho Substituent Effect in Alkaline Hydrolysis of Phenyl Esters of Substituted Benzoic Acids in Water." Collection of Czechoslovak Chemical Communications 71, no. 1 (2006): 107–28. http://dx.doi.org/10.1135/cccc20060107.

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The second-order rate constants k2 for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5 (X = H, 3-Cl, 3-NO2, 3-CH3, 4-NO2, 4-Cl, 4-F, 4-CH3, 4-OCH3, 4-NH2, 2-NO2, 2-CN, 2-F, 2-Cl, 2-Br, 2-I, 2-CH3, 2-OCH3, 2-CF3, 2-NH2), and of substituted phenyl esters of benzoic acid, C6H5CO2C6H4-X (X = 2-I, 2-CF3, 2-C(CH3)3, 4-Cl, 4-CH3, 4-OCH3, 4-NH2), have been measured spectrophotometrically in water at 25 °C. The substituent effect in alkaline hydrolysis of phenyl esters of para-substituted benzoic acids, similar to that for ethyl esters of para-sub

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27

Exner, Otto, and Stanislav Böhm. "Resonance Energy in Benzene Derivatives with a Variable Functional Group." Collection of Czechoslovak Chemical Communications 66, no. 11 (2001): 1623–37. http://dx.doi.org/10.1135/cccc20011623.

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Three isodesmic reactions were investigated in which a variable substituent is transferred from a saturated to an unsaturated hydrocarbon residue: ethane → ethene, methane → benzene, ethane → benzene. Their reaction energies could serve as a measure of substituent resonance ability. They were calculated for 31 substituents by the density functional theory (DFT) at the B3LYP/6-311+G(d,p) level, and served as a model for systematic comparison of the DFT energies and experimental enthalpies of formation ∆fH°(298). It turned out that calculations at this level are more reliable than experiments; t

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28

da Silva Corrêa, Carlos M. M., M. Daniela C. M. Fleming, M. Augusta B. C. S. Oliveira, and Ermelinda M. J. Garrido. "The importance of polar, resonance, steric and solvent effects in the addition of sulfonyl radicals to alkenes." J. Chem. Soc., Perkin Trans. 2, no. 9 (1994): 1993–2000. http://dx.doi.org/10.1039/p29940001993.

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Toteva, Maria M., and John P. Richard. "Structure−Reactivity Relationships for Addition of Sulfur Nucleophiles to Electrophilic Carbon: Resonance, Polarization, and Steric/Electrostatic Effects." Journal of the American Chemical Society 122, no. 45 (2000): 11073–83. http://dx.doi.org/10.1021/ja0021868.

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30

Campanelli, Anna Rita, Aldo Domenicano, and Fabio Ramondo. "Electronegativity, Resonance, and Steric Effects and the Structure of Monosubstituted Benzene Rings: An ab Initio MO Study." Journal of Physical Chemistry A 107, no. 33 (2003): 6429–40. http://dx.doi.org/10.1021/jp030031r.

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Büker, Heinz-Hermann, and Hans-Friedrich Grützmacher. "A fourier transform-ion cyclotron resonance study of steric effects on proton transfer reactions of polyalkyl benzenes." International Journal of Mass Spectrometry and Ion Processes 109 (November 1991): 95–104. http://dx.doi.org/10.1016/0168-1176(91)85099-8.

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32

Nascimento, Marcelo G., and Marco Antonio Bueno Filho. "ANALYSING EXPERIENCED ORGANIC CHEMISTRY TEACHERS’ TEACHING PLANS AND TASK PERFORMANCES BASED ON THE THEORY OF CONCEPTUAL FIELDS." Problems of Education in the 21st Century 67, no. 1 (2015): 81–94. http://dx.doi.org/10.33225/pec/15.67.81.

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This research analyses two experienced Organic Chemistry teachers’ teaching plans and task performances. The recorded audiovisual interviews were analyzed with computer assisted qualitative data analysis software (CAQDAS). Based on the Theory of Conceptual Fields, the teachers used an energetic-structural resolution approach characterized by the simultaneous use of structural field (SCF) and thermodynamics (TCF) articulated electronegativity, polar covalent bond, steric effects, inductive effects, resonance, aromaticity and stereochemistry. The development of the lesson plans indicated more em

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33

Charton, Marvin. "The Nature and Transmission of Substituent Electrical Effects in Alicyclic Solvolysis." Collection of Czechoslovak Chemical Communications 64, no. 11 (1999): 1849–76. http://dx.doi.org/10.1135/cccc19991849.

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The correlation of rate constants taken from the literature for 2-exo- and 2-endo-norbornyl derivatives substituted in positions 1, 4, 5-exo, 6-exo, 6-endo, and 7-anti with the triparametric LDR equation and relationships derived from it has been carried out. A delocalized (resonance) electrical effect has been found in all but the 4-substituted derivatives. The resonance effect may be somewhat greater when the leaving group is exo than when it is endo. Steric effects occur in the 6-endo-substituted derivatives. The transition state resembles a classical carbocation rather than the nonclassica

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34

Luo, Yu-Ran, and Philip D. Pacey. "Generalization of an empirical model for bond dissociation energies." Canadian Journal of Chemistry 71, no. 4 (1993): 572–77. http://dx.doi.org/10.1139/v93-079.

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A relationship between homolytic bond dissociation energies (BDEs) of C—X bonds and the electronegativity of X and the degree of methyl substitution of C has been extended. The range of leaving groups, X, now includes SiH3, GeH3, and PH2 and a variety of C-, N-, and O-centred radicals. Alkyl groups with ethyl and propyl chains attached to the radical centre have been incorporated. Steric effects, including those in bulky silanes, have been treated. The method is believed to be generally applicable where resonance and ring strain are not significant. BDEs for 73 bonds have been calculated; in t

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35

Fraser, Robert R., and Neil C. Faibish. "On the purported axial preference in 2-methylthio and 2-methoxycyclohex-anones: steric effects versus orbital interactions." Canadian Journal of Chemistry 73, no. 1 (1995): 88–94. http://dx.doi.org/10.1139/v95-013.

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The value for the equilibrium constant representing the ratio of equatorial to axial conformers for 2-methylthio- and 2-methoxycyclohexanone has been measured in five solvents using 500 MHz 1H nuclear magnetic resonance. In cyclohexane solvent, the methylthio group is found to have a large axial preference while that for the methoxy is negligible. For both compounds the equilibrium shows a strong solvent dependence. Comparison of these results with those known for the halo derivatives shows the amount of axial to increase in the order: fluoro, methoxy, chloro, bromo, and methylthio. With the a

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Nakata, Kazuhide, Mizue Fujio, Yoshihiro Saeki, Masaaki Mishima, Yuho Tsuno, and Kichisuke Nishimoto. "Ab initio MO study of benzylic cations?2. Steric effects on the resonance interaction and on the resonance demand in the Yukawa-Tsuno equation." Journal of Physical Organic Chemistry 9, no. 8 (1996): 573–82. http://dx.doi.org/10.1002/(sici)1099-1395(199608)9:8<573::aid-poc817>3.0.co;2-2.

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Bates, Andrew C., Kameron L. Klugh, Anna O. Galaeva, et al. "Optimizing Therapeutics for Intratumoral Cancer Treatments: Antiproliferative Vanadium Complexes in Glioblastoma." International Journal of Molecular Sciences 26, no. 3 (2025): 994. https://doi.org/10.3390/ijms26030994.

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Glioblastoma, an aggressive cancer, is difficult to treat due to its location, late detection, drug resistance, and poor absorption of chemotherapeutics. Intratumoral drug administration offers a promising potential treatment alternative with localized delivery and minimal systemic toxicity. Vanadium(V) coordination complexes, incorporating Schiff base and catecholate ligands, have shown effects as antiproliferative agents with tunable efficacy and reactivity, stability, steric bulk, hydrophobicity, uptake, and toxicity optimized for the intratumoral administration vehicle. A new series of oxo

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Smith, Peter, and Jill Suzanne Robertson. "Electron paramagnetic resonance study of the reactions of the spin trap 3,5-dibromo-4-nitrosobenzenesulfonate." Canadian Journal of Chemistry 66, no. 5 (1988): 1153–58. http://dx.doi.org/10.1139/v88-189.

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Using rapid-mixing, continuous-flow TiCl3-based techniques and also by means of static-sample studies involving the thermal decomposition of symmetric aliphatic azo compounds, we have characterized by electron paramagnetic resonance 22 spin adducts of 3,5-dibromo-4-nitrosobenzenesulphonate, 1, in aqueous solution at 25 °C. These spin adducts, all nitroxides, exhibit a moderately wide range of a-nitrogen and β-CH proton splitting constants, which we discuss in terms of steric and electronic effects. In connection with these studies, blank experiments showed that aqueous solutions of 1 gave no r

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Perjéssy, Alexander, Danuta Rasala, Piotr Tomasik, and Ryszard Gawinecki. "The wavenumbers of NO2 stretching vibrations and transmission of substituent effects in 2- and 4-substituted 3-nitropyridine series." Collection of Czechoslovak Chemical Communications 50, no. 11 (1985): 2443–52. http://dx.doi.org/10.1135/cccc19852443.

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The wavenumbers of both the symmetric and asymmetric stretching vibrations of the nitro group were measured in chloroform for the series of 2-X- and 4-X-substituted 3-nitropyridines as well as for o-X-substituted nitrobenzenes. The νas(NO2) and νs(NO2) values of both nitropyridine series were compared with those of corresponding nitrobenzenes. It has been found that the substituent effects in pyridines are transmitted to the 3-nitro group more readily from the 4-position, than from the 2-position. This transmission in 2-X-substituted 3-nitropyridines is comparable with that in the series of o-

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40

De Keijzer, A. E. H., and H. M. Buck. "ELECTRON SPIN RESONANCE STUDY OF PHOSPHORANYL RADICALS I. INFLUENCE OF STERIC AND ELECTRONIC EFFECTS ON RADICAL FORMATION IN SOLUTION." Phosphorous and Sulfur and the Related Elements 31, no. 3-4 (1987): 203–14. http://dx.doi.org/10.1080/03086648708080639.

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Bisht, Harender S., Siddharth S. Ray, and Alok K. Chatterjee. "Resonance, polar, and steric effects of substituent on monomer reactivity in radical polymerization of alkyl 4-vinylbenzoate and butylacrylate." Journal of Polymer Science Part A: Polymer Chemistry 41, no. 12 (2003): 1864–66. http://dx.doi.org/10.1002/pola.10730.

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DA SILVA CORREA, C. M. M., M. D. C. M. FLEMING, M. A. B. C. S. OLIVEIRA, and E. M. J. GARRIDO. "ChemInform Abstract: The Importance of Polar, Resonance, Steric and Solvent Effects in the Addition of Sulfonyl Radicals to Alkenes." ChemInform 26, no. 8 (2010): no. http://dx.doi.org/10.1002/chin.199508087.

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Jiang, Ning, Wei Chen, Prithiviraj Jothikumar та ін. "Effects of anchor structure and glycosylation of Fcγ receptor III on ligand binding affinity". Molecular Biology of the Cell 27, № 22 (2016): 3449–58. http://dx.doi.org/10.1091/mbc.e16-06-0470.

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Isoforms of the Fcγ receptor III (FcγRIII or CD16) are cell surface receptors for the Fc portion of IgG and important regulators of humoral immune responses. Different ligand binding kinetics of FcγRIII isoforms are obtained in three dimensions by surface plasmon resonance and in two dimensions by a micropipette adhesion frequency assay. We show that the anchor structure of CD16 isoforms isolated from the cell membrane affects their binding affinities in a ligand-specific manner. Changing the receptor anchor structure from full to partial to none decreases the ligand binding affinity for human

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44

Nummert, Vilve, and Mare Piirsalu. "Separation of ortho Inductive, Resonance and Steric Terms in Alkaline Hydrolysis of Substituted Phenyl Benzoates and Phenyl Tosylates." Collection of Czechoslovak Chemical Communications 67, no. 12 (2002): 1833–57. http://dx.doi.org/10.1135/cccc20021833.

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The second-order rate constants k2 (l mol-1 s-1) for the alkaline hydrolysis of meta-, para- and ortho-substituted phenyl benzoates C6H5CO2C6H4-X and phenyl tosylates 4-CH3-C6H4SO2OC6H4-X in aqueous 5.3 M NaClO4 have been measured spectrophotometrically at various temperatures. The log k values at a single temperature were analysed according to the equations log km,p = log k0 + (ρ)°m,pσ°, log kortho = log k0+ (ρI)orthoσI + (ρR)orthoσR° + δorthoυ and log km,p,ortho = log k0+ (ρI)orthoσI + (ρI)metaσI + (ρI)paraσI + (ρR)orthoσR° + (ρR)metaσR° + (ρR)paraσR° + δorthoυ. In the case of various temper

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Weinhold, Frank. "“Noncovalent Interaction”: A Chemical Misnomer That Inhibits Proper Understanding of Hydrogen Bonding, Rotation Barriers, and Other Topics." Molecules 28, no. 9 (2023): 3776. http://dx.doi.org/10.3390/molecules28093776.

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We discuss the problematic terminology of “noncovalent interactions” as commonly applied to hydrogen bonds, rotation barriers, steric repulsions, and other stereoelectronic phenomena. Although categorization as “noncovalent” seems to justify classical-type pedagogical rationalizations, we show that these phenomena are irreducible corollaries of the same orbital-level conceptions of electronic covalency and resonance that govern all chemical bonding phenomena. Retention of such nomenclature is pedagogically misleading in supporting superficial dipole–dipole and related “simple, neat, and wrong”

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Li, Tianze, Min Lv, Houpeng Wen, et al. "Synthesis of Piperine-Based Ester Derivatives with Diverse Aromatic Rings and Their Agricultural Bioactivities against Tetranychus cinnabarinus Boisduval, Aphis citricola Van der Goot, and Eriosoma lanigerum Hausmann." Insects 14, no. 1 (2022): 40. http://dx.doi.org/10.3390/insects14010040.

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Exploration of plant secondary metabolites or by using them as leads for development of new pesticides has become one of the focal research topics nowadays. Herein, a series of new ester derivatives of piperine were prepared via the Vilsmeier–Haack–Arnold (VHA) reaction, and their structures were characterized by infrared spectroscopy (IR), melting point (mp), proton nuclear magnetic resonance spectroscopy (1H NMR), and carbon nuclear magnetic resonance spectroscopy (13C NMR). Notably, the steric configurations of compounds 6 and 7 were confirmed by single-crystal analysis. Against T. cinnabar

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Colthurst, Matthew J., Angeline JSS Kanagasooriam, Michael SO Wong, Christian Contini, and Andrew Williams. "Alpha-Effect nucleophiles and azide ion: effective charge studies of displacement reactions at esters." Canadian Journal of Chemistry 76, no. 6 (1998): 678–85. http://dx.doi.org/10.1139/v98-009.

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The bimolecular reactions of azide, 2-iodosobenzoate, and acetohydroxamate ions and methoxyamine nucleophiles with substituted phenyl acetates possess Yukawa-Tsuno type correlations with substantial resonance interaction. The rate constants for hydroperoxide ion and the oxyanion of N,N-diethylhydroxylamine obey simple Hammett equations. The reactivities of azide, acetohydroxamate, hydroperoxide, and 2-iodosobenzoate ion nucleophiles exhibit modest alpha -effects when the reactivity in substitution at 4-nitrophenyl acetate is compared with that of phenoxide ions of similar pKa values. The N,N-d

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Kobori, Yasuhiro. "(Invited) Exciton Spin Dynamics of Triplet Pairs for Quantum Sensing." ECS Meeting Abstracts MA2025-01, no. 16 (2025): 1202. https://doi.org/10.1149/ma2025-01161202mtgabs.

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Light-energy conversion processes causing alternations in spin multiplicity are attracting attention, but the development of quantum sensing technology applicable to noisy environment such as inside cells has been unexploited. How to achieve efficient energy conversion with controlling spin quantum coherence is challenging at room temperature. In this study, we investigate the effect of molecular motion on electron spin polarization to control quantum information of four-spin qubits by triplet pairs using steric effects of organic molecules at room temperature. Using continuous-wave time-resol

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Morales-Ríos, Martha S., Oscar R. Suárez-Castillo, Celina Alvarez-Cisneros та Pedro Joseph-Nathan. "13C NMR and crystallographic evidence of push-pull effects in furoindolic β-enamino esters". Canadian Journal of Chemistry 77, № 1 (1999): 130–37. http://dx.doi.org/10.1139/v98-213.

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A series of cyclic enamine derivatives, stabilized through conjugation with an electron-attracting CO2Me group at the β-carbon of the enamine system, has been prepared. The influence of substituents at the vinylogous donor NH2 group on 13C chemical shifts has been investigated, and the results analyzed on the basis of resonance and steric effects on the dipolar charge distribution in the molecule. Intramolecular H-bonding was established for the N-methylated enamines 4a and 4b based on the high-frequency shift of the NH proton and its solvent immutability. Several deuterium-induced isotope eff

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50

Zhang, Fan, Heng Lei, Feng Guo, et al. "Gamma Irradiation-Induced Changes in Microstructure of Cyclic Olefin Copolymer (COC) Revealed by NMR and SAXS Characterization." Polymers 17, no. 13 (2025): 1751. https://doi.org/10.3390/polym17131751.

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Cyclic Olefin Copolymer (COC) is an amorphous thermoplastic polymer synthesized through the catalytic copolymerization of α-olefin and cyclic olefin. When used in pre-filled syringes and pharmaceutical packaging, COCs require radiation sterilization. The radiation sterilization alters the microstructure of COC, which ultimately affects its performance and biosafety. In this study, to investigate the effects of γ-radiation on COC microstructures, ethylene-norbornene copolymers with various compositions, representative of COC, are studied by nuclear magnetic resonance (NMR) and small angle X-ray

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