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Journal articles on the topic 'Substituent position'

Author: Grafiati

Published: 7 June 2025

Last updated: 2 August 2025

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1

Exner, Otto, and Miloš Buděšínský. "Correlation of substituent – inducted chemical shifts of aromatic protons: Substituted benzonitriles and methyl benzoates." Collection of Czechoslovak Chemical Communications 56, no. 11 (1991): 2234–50. http://dx.doi.org/10.1135/cccc19912234.

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Proton NMR spectra in deuteriochloroform are reported for 53 meta- and para-substituted benzonitriles and 61 methyl benzoates. The substituent-induced chemical shifts (SCS) were correlated with dual substituent parameters (DSP), with 13C SCS of the adjoining carbon, and with the other 1H SCS using the principal component analysis (PCA). They are controlled by different factors in each position to the variable substituent. In the position 4 the long-range polar effects, as expressed by DSP, are decisive, the conjugative component being more important. Remarkable is also very close correlation o

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2

Matsumoto, Shoji, Makoto Takamori, and Motohiro Akazome. "Bathochromic Shift of Fluorescence Peak in Dipyrrolo[1,2-a:2′,1′-c]quinoxaline by Introducing Each of Electron-Donating and Electron-Withdrawing Substituent." Molecules 28, no. 7 (2023): 2896. http://dx.doi.org/10.3390/molecules28072896.

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Development of organic fluorophore is an important theme. Especially, the fluorophores with longer fluorescence peaks are useful to biological probes. One of the methods to change the fluorescence peak is the introduction of substituents. However, opposing characteristics of the substituents lead to different changes in the fluorescence peaks. Furthermore, the introduction of the substituent also affects their electric properties. Thus, if the materials were developed with the substituent effect on the optical and electric properties separately, it will be useful to design the functional mater

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3

Pytela, Oldřich. "Chemometric Analysis of Substituent Effects. I. Substituent Effects on the Dissociation of Monosubstituted Benzoic Acids." Collection of Czechoslovak Chemical Communications 59, no. 1 (1994): 159–74. http://dx.doi.org/10.1135/cccc19940159.

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Forty-six representative sets of data relating to the dissociation of monosubstituted benzoic acids in various solvents were extracted from the literature. The set of substituents included 25 common substituents in the meta position and the same number of substituents in the para position. Hydrogen served as the reference standard. The sets were subjected to regression analysis using conventional empirical models. The Hammett model was found to be valid within the limits of experimental error. The Taft model with the σR0, σR+ and σR- parameters is the best model to account for the substituent

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4

Harsanyi, MC, RK Norris, G. Sze, and PK Witting. "Substituent-Dependent Nitration of 9-Substituted 9,10-Dihydro-9,10-ethanoanthracenes." Australian Journal of Chemistry 48, no. 12 (1995): 1949. http://dx.doi.org/10.1071/ch9951949.

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Mononitration of 9-substituted ethanoanthracenes, bearing Me, But, F, Br, I, OMe , NO2, CN, CHO or CO2Me substituents at the bridgehead carbon, was found to occur exclusively at the β-positions of the aromatic ring. The mononitro products were isolated, identified by 1H n.m.r. spectroscopy, and their relative proportions were estimated by quantitative g.l.c . and/or by 1H n.m.r. spectroscopy. For all the above substrates the proportion of nitration at the β-position meta to the bridgehead carbon bearing the substituent [to give compounds of the general form (4)] was greater than the proportion

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5

Zhou, Yi-Fan, Wen-Yan Chang, Jing-Zhe Chen, et al. "Substituent-mediated quantum interference toward a giant single-molecule conductance variation." Nanotechnology 33, no. 9 (2021): 095201. http://dx.doi.org/10.1088/1361-6528/ac3b84.

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Abstract Quantum interference (QI) in single molecular junctions shows a promising perspective for realizing conceptual nanoelectronics. However, controlling and modulating the QI remains a big challenge. Herein, two-type substituents at different positions of meta-linked benzene, namely electron-donating methoxy (–OMe) and electron-withdrawing nitryl (–NO2), are designed and synthesized to investigate the substituent effects on QI. The calculated transmission coefficients T(E) indicates that –OMe and –NO2 could remove the antiresonance and destructive quantum interference (DQI)-induced transm

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6

Janowska, Sara, Joanna Stefańska, Dmytro Khylyuk, and Monika Wujec. "The Importance of Substituent Position for Antibacterial Activity in the Group of Thiosemicarbazide Derivatives." Molecules 29, no. 6 (2024): 1333. http://dx.doi.org/10.3390/molecules29061333.

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The search for new antibacterial compounds is still a huge challenge for scientists. Each new chemotherapy drug is not 100% effective when introduced into treatment. Bacteria quickly become resistant to known structures. One promising group of new compounds is thiosemicarbazides. In the presented work, we looked for the relationship between structure and antibacterial activity within the group of thiosemicarbazide derivatives. This is a continuation of our previous work. Here, we decided to check to what extent the position of the 3-methoxyphenyl substituent affects potency. We obtained new st

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7

Yang, Shuibo, Bin Sun, Zhongping Ou та ін. "β-Nitro-substituted free-base, iron(III) and manganese(III) tetraarylporphyrins: synthesis, electrochemistry and effect of the NO2 substituent on spectra and redox potentials in non-aqueous media". Journal of Porphyrins and Phthalocyanines 17, № 08n09 (2013): 857–69. http://dx.doi.org/10.1142/s1088424613500612.

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Two free-base and four metal derivatives of substituted tetraarylporphyrins containing a nitro-substituent on the β-pyrrole position of the macrocycle were synthesized and characterized by UV-vis, FTIR, 1 H NMR and mass spectrometry as well as electrochemistry and spectroelectrochemistry in non-aqueous media. The porphyrins are represented as ( NO 2 TmPP ) M and ( NO 2 TdmPP ) M , where M = 2 H , Fe III Cl or Mn III Cl , m is a CH 3 group on the para-position of the four meso-phenyl rings of the tetraphenylporphyrin (TPP) and dm represents two OCH 3 substituents on the meta-positions of each p

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8

Millheim, Alexandra Cruz, Enric Ponzano, and Albert Moyano. "Substituent Effects in the Photophysical and Electrochemical Properties of Meso-Tetraphenylporphyrin Derivatives." Molecules 29, no. 15 (2024): 3689. http://dx.doi.org/10.3390/molecules29153689.

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Porphyrins were identified some years ago as a promising, easily accessible, and tunable class of organic photoredox catalysts, but a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state redox potentials of these compounds is still lacking. We prepared a set of known functionalized porphyrin derivatives containing different substituents either in one of the meso positions or at a β-pyrrole carbon, and we determined their ground- and (singlet) excited-state redox potentials. We found that while the estimat

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9

Simeonova, Kristina B., Ana I. Koleva, Nevena I. Petkova-Yankova, et al. "Elucidating the Mechanism of Coumarin Homodimerization Using 3-Acetylcoumarin Derivatives." Molecules 30, no. 3 (2025): 651. https://doi.org/10.3390/molecules30030651.

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The current study is a continuation of our previous investigations into the radical homodimeric reaction mechanism of 3-acetylcoumarin. In the current study, the effects of different substituents on the coumarin ring of 3-acetylcoumarin are investigated both experimentally and theoretically. Several 3-acetylcoumarin derivatives (substituted at C-6, C-7, and C-8) were tested in the optimized reaction conditions under ultrasound irradiation, and biscoumarin species were isolated and characterized. The elucidation of the substituent’s effect was further investigated by means of DFT calculations (

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10

Yano, Masafumi, Mai Sasaoka, Kohei Tamada, et al. "Substituent Control of Near-Infrared Absorption of Triphenylamine Radical Cation." Colorants 1, no. 3 (2022): 354–62. http://dx.doi.org/10.3390/colorants1030021.

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Five triphenyltriphenylamines with various substituents were investigated as precursors for near-infrared absorbing materials. Cyclic voltammetry (CV) studies showed that they all give stable radical cations in solution. The radical cations obtained by one-electron chemical oxidation of these compounds show strong absorption in the near-infrared region, and the position of the absorption is strongly influenced by the substituent. DFT (density functional theory) calculations suggest that the introduction of stronger electron-donating substituents would result in a smaller HOMO–SOMO energy gap a

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11

Petrichenko, Oksana, Aiva Plotniece, Karlis Pajuste, et al. "Evaluation of Physicochemical Properties of Amphiphilic 1,4-Dihydropyridines and Preparation of Magnetoliposomes." Nanomaterials 11, no. 3 (2021): 593. http://dx.doi.org/10.3390/nano11030593.

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This study was focused on the estimation of the targeted modification of 1,4-DHP core with (1) different alkyl chain lengths at 3,5-ester moieties of 1,4-DHP (C12, C14 and C16); (2) N-substituent at position 1 of 1,4-DHP (N-H or N-CH3); (3) substituents of pyridinium moieties at positions 2 and 6 of 1,4-DHP (H, 4-CN and 3-Ph); (4) substituent at position 4 of 1,4-DHP (phenyl and napthyl) on physicochemical properties of the entire molecules and on the characteristics of the obtained magnetoliposomes formed by them. It was shown that thermal behavior of the tested 1,4-DHP amphiphiles was relate

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12

Barbry, Didier, Bruno Hasiak, Jean-Michel Augait, and Daniel Couturier. "Evolution thermique de N-oxydes de dimethylamino-5 alcanols-1 substitues en 5. Competition entre rearrangements de cope et de Meisenheimer." Collection of Czechoslovak Chemical Communications 50, no. 4 (1985): 956–61. http://dx.doi.org/10.1135/cccc19850956.

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The effect of the substituent R in the position was studied in the decomposition of 1,5-aminoalcohol N-oxides: Meisenheimer rearrangement takes place when R is the vinyl group but is not observed with the phenyl substituent; elimination to alkenol only affects the more acidic hydrogen atom when R is the allyl or benzyl group; with substituents inducing less important electronic effects (methyl, ethyl), the reaction yields an alkenols mixture with statistical distribution.

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13

Holík, Miroslav, and Božena Matějková. "Transmission of substituent effects in N-(p-substituted phenyl)-phthalimides." Collection of Czechoslovak Chemical Communications 55, no. 1 (1990): 261–72. http://dx.doi.org/10.1135/cccc19900261.

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Chemical shifts of benzene part of the title compounds have been correlated with substituent chemical shifts (SCS) increments a for 1H and z for 13C NMR spectra. These correlations gave pieces of information not only about the through-conjugation of substituents but also about the change of the twist about the central N-C bond with the change of substituent in the para-position. In such a way the electronic effects of substituents have been studied together with the effects due to conformational changes which manifest themselves with the change in the van der Waals repulsion and/or diamagnetic

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14

Buděšínský, Miloš, Dan Johnels, Ulf Edlund, and Otto Exner. "Carbon-13 substituent-induced chemical shifts in benzene derivatives: Substituted anilines." Collection of Czechoslovak Chemical Communications 56, no. 2 (1991): 368–85. http://dx.doi.org/10.1135/cccc19910368.

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Carbon-13 NMR spectra are reported for 59 meta- and para-substituted anilines in deuterochloroform or in its mixture with hexadeuterodimethyl sulphoxide. The substituent-induced chemical shifts (SCS) of ring carbon atoms in position 4 correlate well with dual substituent parameters (DSP). In the remaining positions correlations are not satisfactory with any kind of known substituent constants. There is, however, a close resemblance between SCS in the same position of meta- and para-substituted anilines and even in other series of aromatic compounds.

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15

Exner, Otto, and Miloš Buděšínský. "Carbon-13 Substituent-Induced Chemical Shifts: Monosubstituted Benzene Derivatives." Collection of Czechoslovak Chemical Communications 57, no. 3 (1992): 497–507. http://dx.doi.org/10.1135/cccc19920497.

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Carbon-13 NMR spectra of twelve monosubstituted benzene derivatives were measured in deuterochloroform. Together with the literature data a set of 35 systematically chosen substituents was obtained on which some thirty correlation equations were tested. As anticipated only substituent chemical shifts (SCS) in the position 4 are controlled by inductive and resonance effects, and can be correlated by dual substituent parameters (DSP). For the other positions DSP were not successful and more sophisticated equations are not much telling. On the other hand, the direct relations between two series o

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16

Özden, Seçkin, Hamide Ertepinar, and Ömer Geban. "QSAR Study on Antibacterial Effects of Benzimidazole and Imidazopyridine Derivatives." Collection of Czechoslovak Chemical Communications 60, no. 12 (1995): 2178–88. http://dx.doi.org/10.1135/cccc19952178.

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A set of benzimidazole (I) and imidazopyridine (II) derivatives previously tested for their antibacterial activities against Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), and Bacillus subtilis (B. subtilis) were analyzed by quantitative structure-activity relationship (QSAR) and the activity contributions for structural and substituent effects were determined using multiple regression procedure. The resulting QSAR revealed that for the activity contribution against S. aureus and P. aeruginosa the substituents of p-position on the phenyl

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17

Banham, Wendy K., John L. Huppatz, and John N. Phillips. "N-Methylanilinocyanoacrylate Photosystem II Inhibitors. Structure-Activity Relationships." Zeitschrift für Naturforschung C 48, no. 3-4 (1993): 136–39. http://dx.doi.org/10.1515/znc-1993-3-404.

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Abstract Many 3-N-methylanilino cyanoacrylate derivatives are potent inhibitors of photosynthetic electron transport at the PS II level in a thylakoid system isolated from Pisum sativum. These inhibitors are somewhat unusual in that they take more than 15 min to equilibrate with the binding site in contrast to most classical PS II inhibitors which tend to equilibrate rapidly i.e. within the mixing time of seconds. The effects of mono-and disubstituents in the aryl nucleus on inhibitory activity were studied. The nature and position of the substituent had no detectable influence on equilibratio

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18

MAYR, Peter, and Bernd NIDETZKY. "Catalytic reaction profile for NADH-dependent reduction of aromatic aldehydes by xylose reductase from Candida tenuis." Biochemical Journal 366, no. 3 (2002): 889–99. http://dx.doi.org/10.1042/bj20020080.

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Kinetic substituent effects have been used to examine the catalytic reaction profile of xylose reductase from the yeast Candida tenuis, a representative aldo/keto reductase of primary carbohydrate metabolism. Michaelis—Menten parameters (kcat and Km) for NADH-dependent enzymic aldehyde reductions have been determined using a homologous series of benzaldehyde derivatives in which substituents in meta and para positions were employed to systematically perturb the properties of the reactive carbonyl group. Kinetic isotope effects (KIEs) on kcat and kcat/Km for enzymic reactions with meta-substitu

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19

Lay, PA, RK Norris, and PK Witting. "Cyclic Voltammetric and E.P.R. Spectroscopic Studies on Apical Substituent Effects in Radical Anions of 9-Substituted and 9,10-Disubstituted Nitroethanoanthracenes." Australian Journal of Chemistry 49, no. 12 (1996): 1279. http://dx.doi.org/10.1071/ch9961279.

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Cyclic voltammetry and electron paramagnetic resonance spectroscopy were used to examine apical substituent effects on the properties of Me2SO solutions of the radical anions from 9-substituted and 9,10-disubstituted 2- and 3-nitro-9,10-dihydro-9,10-ethanoanthracenes (1)-(24). The reductions of the nitro group are, in general, reversible at 100 mV s-1 and at 20°, except where there are coupled intra-or inter-molecular electron or proton transfer reactions with aliphatic bridgehead substituents, such as a carboxylic acid or iodine. The substituent effects for the meta- and para-nitroethanoanthr

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20

Susanthy, Dian, Fadliah, Endang Tri Wahyuni, and Sri Juari Santosa. "Synthesis of Silver Nanoparticles Using o-Hydroxybenzoic, p-Hydroxybenzoic, and o,p-Dihydroxybenzoic Acids as Reducing Agents." Materials Science Forum 901 (July 2017): 26–31. http://dx.doi.org/10.4028/www.scientific.net/msf.901.26.

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Synthesis of silver nanoparticles (AgNPs) by reduction of AgNO3 with o-hydroxybenzoic, p-hydroxybenzoic and o,p-dihydroxybenzoic acids as reducing agents was investigated. This research was conducted to determine the effect of the position and number of hydroxyl groups towards the size, shape and stability of the resulted AgNPs. Surface Plasmon Resonance (SPR) of AgNPs was characterized by UV/Vis spectrophotometer, the shape and size of AgNPs was determined by Transmission Electron Microscope (TEM). The results showed that the reducing agent that has substituents in the para position (p-hydrox

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21

Birsa, Mihail Lucian, and Laura Gabriela Sarbu. "A Structure–Activity Relationship Study on the Antioxidant Properties of Dithiocarbamic Flavanones." Antioxidants 13, no. 8 (2024): 963. http://dx.doi.org/10.3390/antiox13080963.

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The antioxidant properties of 3-dithiocarbamic flavanones have been investigated. The influence of the halogen substituents on ring A of the flavanones and the nature of the secondary amine from the dithiocarbamic moiety have been accounted. The results indicated that the presence of a halogen substituent at the C-8 position of the benzopyran ring induce better antioxidant properties against DPPH and ABTS than butylated hydroxytoluene (BHT) and ascorbic acid. The presence of a halogen substituent at the mentioned position appears to induce a higher stability for a free radical intermediate at

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22

Denner, Toni C., Niels V. Heise, Ahmed Al-Harrasi, and René Csuk. "Synthesis and Enzymatic Evaluation of a Small Library of Substituted Phenylsulfonamido-Alkyl Sulfamates towards Carbonic Anhydrase II." Molecules 29, no. 13 (2024): 3015. http://dx.doi.org/10.3390/molecules29133015.

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A small library of 79 substituted phenylsulfonamidoalkyl sulfamates, 1b–79b, was synthesized starting from arylsulfonyl chlorides and amino alcohols with different numbers of methylene groups between the hydroxyl and amino moieties yielding intermediates 1a–79a, followed by the reaction of the latter with sulfamoyl chloride. All compounds were screened for their inhibitory activity on bovine carbonic anhydrase II. Compounds 1a–79a showed no inhibition of the enzyme, in contrast to sulfamates 1b–79b. Thus, the inhibitory potential of compounds 1b–79b towards this enzyme depends on the substitue

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23

Velihina, Yevgeniia, Maryna Kachaeva, Stepan Pil'o, Viktoriia Moskvina, Olga Shablykina, and Volodymyr Brovarets. "SYNTHESIS OF 4-HETARYL-2-(DICHLOROMETHYL)PYRAZOLO[1,5-a][1,3,5]-TRIAZINES." Ukrainian Chemistry Journal 86, no. 5 (2020): 53–62. http://dx.doi.org/10.33609/2708-129x.86.5.2020.53-62.

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New pyrazolo[1,5-a][1,3,5]triazines with a heteroaromatic substituent in position 4 and dichloromethyl moiety in position 2 were obtained via a heterocyclization reaction of readily available reagents - N-(2,2-dichloro-1-cyanoethenyl)carboxamides and 3(5)-aminopyrazoles. The high efficiency of the proposed method for the synthesis of 2-(dichloromethyl)-pyrazolo[1,5-a][1,3,5]triazines with furan-2-yl, thien-2-yl, and pyridine-3-yl substituents was demonstrated.

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24

Sørensen, Thomas, and Merete Nielsen. "Synthesis, UV/vis spectra and electrochemical characterisation of arylthio and styryl substituted ferrocenes." Open Chemistry 9, no. 4 (2011): 610–18. http://dx.doi.org/10.2478/s11532-011-0040-8.

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AbstractTwo series of substituted ferrocenes were synthesised using either the Horner-Wadsworth-Emmons reaction or monolithiation of ferrocene. The series consist of arylthio- and styryl-ferrocenes with different substituents in the para position of the aryl rings of the systems. The electronic communication was investigated by comparing the substituent effects in absorption spectroscopy and in cyclic voltammetry. A small substituent effect was found in the electronic transitions of the styryl substituted ferrocenes. The oxidation of the ferrocene derivatives showed clear substituent effects a

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25

Waisser, Karel, Milan Peřina, Věra Klimešová, and Jarmila Kaustová. "On the Relationship between the Structure and Antimycobacterial Activity of Substituted N-Benzylsalicylamides." Collection of Czechoslovak Chemical Communications 68, no. 7 (2003): 1275–94. http://dx.doi.org/10.1135/cccc20031275.

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Sixty-six N-benzylsalicylamides substituted in the acyl moiety in positions 3, 4 or 5 and in position 4 on the benzylic aromatic ring were synthesized. The compounds were tested for in vitro antimycobacterial activity against Mycobacterium tuberculosis, Mycobacterium kansasii and Mycobacterium avium. To evaluate structure-antimycobacterial activity relationships (QSARs), approaches based on the Free-Wilson as well as a combination of the Free-Wilson and Hansch methods were employed (substituent constants were used to describe the influence of the benzyl substituents, indicator parameters were

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26

Cameron, Lynn M., Keith Vaughan, and Donald L. Hooper. "Synthesis of a series of 3-aryl-1-methyltriazene 1-oxides with substituents in the ortho or para position in the aryl group." Canadian Journal of Chemistry 70, no. 8 (1992): 2241–44. http://dx.doi.org/10.1139/v92-281.

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A series of 3-aryl-1-methyltriazene 1-oxides, with a variety of substituents in the ortho or para position, have been prepared by coupling of the appropriate diazonium salt with TV-methylhydroxylamine. The substituents range from electron withdrawing, i.e., CO2Et, NO2, CN, COCH3, Br, and CF3, to electron releasing, i.e., OCH3. In all cases studied, the triazenes exist as the 1-oxide tautomer; there is no evidence for the presence of a 3-hydroxy tautomer in any of these cases. The 1-oxide structures have been confirmed by IR and NMR spectroscopy and by elemental analysis of new compounds. In th

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27

Giri, Rajan, Hari K. Namballa, Vishwashiv Emogaje, and Wayne W. Harding. "Structure–Activity Relationship Studies on 6-Chloro-1-phenylbenzazepines Leads to the Identification of a New Dopamine D1 Receptor Antagonist." Molecules 28, no. 16 (2023): 6010. http://dx.doi.org/10.3390/molecules28166010.

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The 1-phenylbenzazepine template has yielded a number of D1R-like ligands, which, though useful as pharmacological tools, have significant drawbacks in terms of selectivity versus D5R as well as pharmacokinetic behavior. A number of 1-phenylbenzazepines contain a 6-chloro functional group, but extensive SAR studies around the 6-chloro-1-phenylbenzazepine framework have not been reported in the literature. To further understand the tolerance of the 6-chloro-1-phenylbenzazepine template for various substituent groups towards affinity and selectivity at D1R, we synthesized two series of analogs w

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Nádvorník, Jiří, and Miroslav Ludwig. "Ortho Effect in Dissociation of Substituted N-Phenylbenzenesulfonamides." Collection of Czechoslovak Chemical Communications 66, no. 9 (2001): 1380–92. http://dx.doi.org/10.1135/cccc20011380.

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Twenty-five 2,2'-disubstituted N-phenylbenzenesulfonamides (2-X-C6H4SO2NHC6H4-Y-2') were synthesised and their purity checked by elemental analysis. This set of model substrates involved all possible combinations of methoxy, methyl, hydrogen, chloro, and nitro substituents. The dissociation constants of the sulfonamides were determined by potentiometric titration in methanol, pyridine, dimethyl sulfoxide, N,N-dimethylformamide, acetone, and acetonitrile. The dissociation constants pKHA obtained were correlated with various sets of substituent constants describing electronic and steric effects

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29

Hnyk, Drahomír. "Principal component analysis of substituent constants." Collection of Czechoslovak Chemical Communications 55, no. 1 (1990): 55–62. http://dx.doi.org/10.1135/cccc19900055.

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The principal component analysis has been applied to a data matrix formed by 7 usual substituent constants for 38 substituents. Three factors are able to explain 99.4% cumulative proportion of total variance. Several rotations have been carried out for the first two factors in order to obtain their physical meaning. The first factor is related to the resonance effect, whereas the second one expresses the inductive effect, and both together describe 97.5% cumulative proportion of total variance. Their mutual orthogonality does not directly follow from the rotations carried out. With the help of

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30

Zhang, Nuonuo, Kanumuri Ramesh Reddy, Jianbing Jiang, Masahiko Taniguchi, Roger D. Sommer, and Jonathan S. Lindsey. "Elaboration of an unexplored substitution site in synthetic bacteriochlorins." Journal of Porphyrins and Phthalocyanines 19, no. 07 (2015): 887–902. http://dx.doi.org/10.1142/s1088424615500534.

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The ability to introduce substituents at designated sites about the perimeter of synthetic bacteriochlorins – analogs of bacteriochlorophylls of bacterial photosynthesis – remains a subject of ongoing study. Here, the self-condensation of a dihydrodipyrrin-dioxolane affords a 5-[2-(trimethylsiloxy)ethoxy]bacteriochlorin. Like a 5-methoxybacteriochlorin, the latter undergoes regioselective bromination at the 15-position, directed by the distal 5-alkoxy group. On the other hand, attempted bromination of a bacteriochlorin bearing a 5-(2-hydroxyethoxy) group resulted in intramolecular ether format

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31

Amador-Balderas, Jorge A., Michael-Adán Martínez-Sánchez, Ramsés E. Ramírez, Francisco Méndez, and Francisco J. Meléndez. "Analysis of the Gas Phase Acidity of Substituted Benzoic Acids Using Density Functional Concepts." Molecules 25, no. 7 (2020): 1631. http://dx.doi.org/10.3390/molecules25071631.

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A theoretical study of the effect of the substituent Z on the gas phase acidity of substituted benzoic acids ZC6H4COOH in terms of density functional theory descriptors (chemical potential, softness and Fukui function) is presented. The calculated gas phase ΔacidG° values obtained were close to the experimental ones reported in the literature. The good relationship between the ΔacidG° values and the electronegativity of ZC6H4COOH and its fragments, suggested a better importance of the inductive than polarizability contributions. The balance of inductive and resonance contributions of the subst

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32

Hayashi, Norihiro, Yoshihiro Nakata, and Akira Yazaki. "New Findings on the Structure-Phototoxicity Relationship and Photostability of Fluoroquinolones with Various Substituents at Position 1." Antimicrobial Agents and Chemotherapy 48, no. 3 (2004): 799–803. http://dx.doi.org/10.1128/aac.48.3.799-803.2004.

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ABSTRACT The present study examined the phototoxicities of a series of 7-(3-aminopyrrolidinyl) quinolones containing various substituents at position 1 (in which the substituent at R8 is a hydrogen or a halogen) by use of a mouse model. For the 7-(3-aminopyrrolidinyl) quinolones with a halogen atom at position 8, well-known substituent groups such as a cyclopropyl, an ethyl, or a difluorophenyl at position 1 were found to be responsible for severe phototoxicity. However, when an aminodifluorophenyl or an isoxazolyl group was placed at position 1, even 8-halogeno quinolones were found to be mil

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33

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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34

Olasunkanmi, L. O., J. Ige, and G. O. Ogunlusi. "Theoretical Study of the Molecular Geometries, Electronic and Thermodynamic Properties of Chlorinated Dipyrido-(3,2-a:,-c)-Phenazine." Journal of Chemistry 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/640649.

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Theoretical study of the molecular geometries, electronic and thermodynamic properties of dipyrido-(3,2-a:,-c)-phenazine (dppz) was carried out in the gas phase under standard conditions using PM6 Hamiltonian in semiempirical model. Effects of chlorine substituents on these properties were also investigated. The results showed that all the electronic and thermodynamic properties investigated were affected by the number and relative position of chlorine substituents. Variations in some properties are not significant for some isomeric congeners, having the same number of chlorine substituents, w

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35

Wieczorkiewicz, Paweł A., Halina Szatylowicz, and Tadeusz M. Krygowski. "Energetic and Geometric Characteristics of Substituents, Part 3: The Case of NO2 and NH2 Groups in Their Mono-Substituted Derivatives of Six-Membered Heterocycles." Symmetry 14, no. 1 (2022): 145. http://dx.doi.org/10.3390/sym14010145.

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Substituted heterocyclic arenes play important roles in biochemistry, catalysis, and in the design of functional materials. Exemplary six-membered heteroaromatic molecules, that differ from benzene by inclusion of one heteroatom, are pyridine, phosphorine, arsabenzene, and borabenzene. This theoretical study concerns the influence of the heteroatom present in these molecules on the properties of substituents of two types: electron-donating (ED) NH2 group and electron-accepting (EA) NO2 group, attached at the 2-, 3-, or 4-position. The effect is evaluated by the energy of interaction (Erel) bet

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36

Tkachuk, N. V., V. O. Yanchenko, and A. M. Demchenko. "Antibacterial and phytotoxic activity of the Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with the donor substituents in the 4th position on heterosystem." Studia Biologica 15, no. 4 (2021): 17–24. http://dx.doi.org/10.30970/sbi.1504.667.

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Background. Triazoles and Schiff’s bases have a high biological activity. For the practical use of the derivatives, their low toxicity is important. The purpose of this work was to investigate the antibacterial and phytotoxic properties of Schiff’s bases of 5-phenyl-4-amino-3-mercapto-4H-1,2,4-triazole with donor substituents in the 4th position of heterosystem. Materials and methods. In the study of antibacterial activity of the derivatives, corrosion-active 4-day association cultures of ammonifying and sulfate-reducing bacteria were used as a test culture of microorganisms. Sensitivity of ba

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37

Irie, Kazuhiro, Nobuyuki Hagiwara, Harukuni Tokuda, and Koichi Koshimizu. "Structure-activity studies of the indole alkaloid tumor promoter teleocidins." Carcinogenesis 8, no. 4 (1987): 547–52. http://dx.doi.org/10.1093/carcin/8.4.547.

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Abstract New teleocidin derivatives with various substituents at positions 2, 5 and 7 of the indole ring were prepared from (—)-indolactam V, which is the fundamental structure of teleocidins and has a tumor-promoting activity, to examine the contribution of the alkyl substituents of teleocidins to the activity. Their possible tumor-promoting activities in vivo were evaluated by Epstein—Barr virus early antigen-inducing activity and inhibition of specific binding of [3H]TPA to a mouse epidermal particulate fraction. These two biological activities correlated well for each derivative. Large sub

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38

Ye, Ding, Kuan Zhang, Hua-feng Chen, Shu-fan Yin та Ying Li. "4-Formylphenyl 2,3,4,6-tetra-O-acetyl-β-D-allopyranoside". Acta Crystallographica Section E Structure Reports Online 65, № 6 (2009): o1338. http://dx.doi.org/10.1107/s1600536809018248.

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The title compound, C21H24O11, crystallizes exclusively as the β-anomer. The substituent of the protected sugar at position C-3 is in the axial position, while all other groups are in equatorial positions. The pyranoside ring adopts a stable chair conformation.

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39

Pişkin, Mehmet, Nursel Can, Zafer Odabaş, and Ahmet Altındal. "Toluene vapor sensing characteristics of novel copper(II), indium(III), mono-lutetium(III) and tin(IV) phthalocyanines substituted with 2,6-dimethoxyphenoxy bioactive moieties." Journal of Porphyrins and Phthalocyanines 22, no. 01n03 (2018): 189–97. http://dx.doi.org/10.1142/s1088424617500900.

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This study presents the synthesis, characterization and toluene sensing properties of copper(II), indium(III) acetate, mono-lutetium(III) acetate and tin(IV) phthalocyanines substituted with 2,6-dimethoxyphenol bioactive groups at the peripheral and non-peripheral positions. The effects of the substituent’s position on the toluene vapor detection capabilities of these compounds were investigated. Adsorption data were analyzed by using first-order and Elovich equations in order to investigate the adsorption kinetics. It was found that the kinetics of the toluene adsorption strongly depends on t

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40

Holík, Miroslav, Zdeněk Friedl, and Štefan Marchalín. "Multivariate Regression with Substituent Shift Increments. III. 2,5-Disubstituted Furans." Collection of Czechoslovak Chemical Communications 64, no. 10 (1999): 1696–708. http://dx.doi.org/10.1135/cccc19991696.

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Six series of 2-X-5-Y-substituted furans were used for multivariate regression of 13C NMR chemical shifts with four substituent shift increments (SSI). Some of these series were measured in CDCl3 and DMSO-d6 on different spectrometers to exclude possible sources of deviation from the general trends. Program ASSIGN was written for visual and numerical estimation of correct assignment of 13C NMR spectra in the series of derivatives. Multivariate regression proved that the corresponding position in benzenes and furans are not affected by the substituents in the same way: in 2-X-5-Y-substituted fu

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41

Cheng-Sánchez, Iván, José A. Torres-Vargas, Beatriz Martínez-Poveda, et al. "Synthesis and Antitumor Activity Evaluation of Compounds Based on Toluquinol." Marine Drugs 17, no. 9 (2019): 492. http://dx.doi.org/10.3390/md17090492.

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Encouraged by the promising antitumoral, antiangiogenic, and antilymphangiogenic properties of toluquinol, a set of analogues of this natural product of marine origin was synthesized to explore and evaluate the effects of structural modifications on their cytotoxic activity. We decided to investigate the effects of the substitution of the methyl group by other groups, the introduction of a second substituent, the relative position of the substituents, and the oxidation state. A set of analogues of 2-substituted, 2,3-disubstituted, and 2,6-disubstituted derived from hydroquinone were synthesize

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42

Mravljak, Janez, Lara Slavec, Martina Hrast, and Matej Sova. "Synthesis and Evaluation of Antioxidant Properties of 2-Substituted Quinazolin-4(3H)-ones." Molecules 26, no. 21 (2021): 6585. http://dx.doi.org/10.3390/molecules26216585.

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Quinazolinones represent an important scaffold in medicinal chemistry with diverse biological activities. Here, two series of 2-substituted quinazolin-4(3H)-ones were synthesized and evaluated for their antioxidant properties using three different methods, namely DPPH, ABTS and TEACCUPRAC, to obtain key information about the structure–antioxidant activity relationships of a diverse set of substituents at position 2 of the main quinazolinone scaffold. Regarding the antioxidant activity, ABTS and TEACCUPRAC assays were more sensitive and gave more reliable results than the DPPH assay. To obtain

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43

Svoboda, Jiří, Pavel Pihera, Petr Sedmera, and Jaroslav Paleček. "Electrophilic Substitution Reactions of [1]Benzothieno[3,2-b]furan." Collection of Czechoslovak Chemical Communications 61, no. 6 (1996): 888–900. http://dx.doi.org/10.1135/cccc19960888.

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In chlorination, bromination, iodination, nitration, sulfonation, formylation, and trifluoroacetylation of [1]benzothieno[3,2-b]furan (1) the substituent enters the 2-position. The said halogenations go by the addition-elimination mechanism. When the substitution is continued, the second substituent enters the 6-position of heterocycle 1. The 1H and 13C NMR spectra have been completely assigned. Substituent effects on NMR parameters are discussed.

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44

Jezuita, Anna, Krzysztof Ejsmont, and Halina Szatylowicz. "Substituent effects of nitro group in cyclic compounds." Structural Chemistry 32, no. 1 (2020): 179–203. http://dx.doi.org/10.1007/s11224-020-01612-x.

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AbstractNumerous studies on nitro group properties are associated with its high electron-withdrawing ability, by means of both resonance and inductive effect. The substituent effect of the nitro group may be well described using either traditional substituent constants or characteristics based on quantum chemistry, i.e., cSAR, SESE, and pEDA/sEDA models. Interestingly, the cSAR descriptor allows to describe the electron-attracting properties of the nitro group regardless of the position and the type of system. Analysis of classical and reverse substituent effects of the nitro group in various

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45

Radkowska, Ilona, and Piotr Bragiel. "1-Naphthols as components for multifunctional material systems (MFMS): the molecular modeling approach." Structural Chemistry 32, no. 1 (2020): 259–73. http://dx.doi.org/10.1007/s11224-020-01674-x.

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AbstractIncreasing research interests have been paid to developing efficient multifunctional material systems (MFMS) by using various composite materials, owing to their useful properties and good stability. Here, we systematically studied 1-naphthols, especially how the type and position of a substituent influence the reactivity and properties, using different electron-directing groups. During computations, important preparation guidelines for thiol derivatives of 1-naphthol were obtained. It is very interesting to note that some molecules could exhibit intramolecular O–H–O interactions. Care

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46

Birsa, Mihail Lucian, and Laura Gabriela Sarbu. "Novel Dithiocarbamic Flavanones with Antioxidant Properties—A Structure–Activity Relationship Study." International Journal of Molecular Sciences 25, no. 24 (2024): 13698. https://doi.org/10.3390/ijms252413698.

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The antioxidant properties of some 3-dithiocarbamic flavanones were investigated. Based on a previous study, we selected three frameworks that proved to be the most active ones. By varying the nature of the substituent at the para-position of flavanone ring B, a structure–activity relationship study on radical scavenging activities was performed. The influence of these substituents (H, F, Cl, Br and I) was evaluated in relation to DPPH, ABTS and FRAP. The results indicated that the presence of the halogen substituent induced better antioxidant properties than ascorbic acid and BHT. The radical

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47

Kulhánek, Jiří, and Oldřich Pytela. "Chemometric Analysis of Substituent Effects. VI. A Study of ortho Effect in Dissociation of 2,6-Disubstituted Benzoic Acids." Collection of Czechoslovak Chemical Communications 60, no. 5 (1995): 829–40. http://dx.doi.org/10.1135/cccc19950829.

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Ten 2,6-disubstituted benzoic acids have been synthesized containing all possible combinations of the following substituents: CH3, OCH3, Cl, and NO2. The dissociation constants of these acids have been measured by potentiometric titration in methanol, acetone, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, and 1,2-dichloroethane. The experimental data obtained together with the pK values of 2-substituted benzoic acids in the same solvents have been analyzed from the point of view of ortho effect and additivity of disubstitution. The mutual interaction between substituents was f

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48

Sandmann, Gerhard, and Peter Böger. "Structure-Activity Correlations of Substituted 3(2H)Furanones Chemically Related to the Bleaching Herbicide Flurtamone." Zeitschrift für Naturforschung C 48, no. 3-4 (1993): 312–16. http://dx.doi.org/10.1515/znc-1993-3-432.

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The bleaching herbicide flurtamone shows a concentration-dependent inhibition of phytoene desaturase activity in a cell-free assay. Structure-activity studies were carried out with 26 derivatives. For this purpose, I50 values for inhibition of formation of colored carotenoids in cultures of Synechococcus and with some selected compounds in vitro inhibition data were measured. For meta-substituted 4-phenyl derivatives a quantitative structure-activity correlation was calculated. Regression analysis show ed a significant contribution of lipophilicity π and steric parameter B2 of the substituents

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49

Shorter, J. "Compilation and Critical Evaluation of Structure-Reactivity Parameters and Equations. I. Values of σm and σp Based on the Ionization of Substituted Benzoic Acids in Water at 25°C". Australian Journal of Chemistry 48, № 8 (1995): 1453. http://dx.doi.org/10.1071/ch9951453.

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Data have been compiled for the pKa values in water at 25°C of about 60 meta- or para-substituted benzoic acids, with a view to proposing recommended values of Hammett substituent constants, σ. The number of substituents covered is about one-half of this number, but for certain substituents data are not available for both the meta and para position. The amount and the reliability of the data vary greatly from one acid to another. Critical appraisal leads to the classification of the substituents and their σ values as belonging to a First Division (with more reliable data) or a Second Division

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Kakeya, Kazuhisa, Atsuko Shimizu, Kenta Akasaka, and Tadashi Mizutani. "Substituent effects on selectivity of coupled oxidation of iron tetraphenylporphyrins." Journal of Porphyrins and Phthalocyanines 19, no. 05 (2015): 726–33. http://dx.doi.org/10.1142/s1088424615500455.

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Coupled oxidation of iron tetraphenylporphyrins bearing either a OMe , Me , F , Cl , COOMe , CF 3 or CN group in the para-position of the phenyl groups gave tetraarylbiladien-ab-1-one and triarylbilindione. The ratios of the yields of the former to those of the latter were linearly correlated with the Hammett substituent constants σp+, with a positive slope (Δρ = 0.64). The Hammett plot of the oxidation rate vs. the substituent constant σp also showed a positive slope (ρ = 0.30). These substituent effects suggest that a nucleophilic step is included in the formation of bilindione. Coupled oxid

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