Results 1 to 10 of about 3,044 (143)

Determination of Hammett Sigma Constants by Intramolecular Hydrogen Bonding [PDF]

Nature, 1958
THE extensive literature that exists concerning Hammett's σ-constants has been subjected to several recent reviews, including a compilation and examination of available data1, a discussion of the significance and limitations of the concepts involved2, and an attempt to deduce best values and probable errors for the σ-values3.
A. T. SHULGIN, A. W. BAKER
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Donor Strengths Determination of Pnictogen and Chalcogen Ligands by the Huynh Electronic Parameter and Its Correlation to Sigma Hammett Constants [PDF]

Chemistry – A European Journal, 2019
AbstractThe suitability and accuracy of the Huynh electronic parameter (HEP) was further tested to reveal remote substituent effects in pyridines, which are located five or six bonds away from the reporter probe. These values show an excellent correlation to Hammett σ‐constants of the respective substituents with coefficients of R2=0.9856 (σm) and R2=0.
Qiaoqiao Teng, Ping Siang Ng, Jia Nuo Leung, Han Vinh Huynh   +3 more
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DFT study, and natural bond orbital (NBO) population analysis of 2-(2-Hydroxyphenyl)-1-azaazulene tautomers and their mercapto analouges [PDF]

Scientific Reports
Theoretical research on the keto-enol tautomerization of 2-(2-Hydroxyphenyl)-1-aza azulene (2HPhAZ) and its thiol-thione (2MPhAZ) analouge has been performed using the density functional B3LYP method with the 6–311 +  + G(2d,2p) basis set in gas and ...
Shimaa Abdel Halim, Asmaa B. El-Meligy, Ahmed M. El-Nahas, Safinaz H. El-Demerdash   +3 more
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Determination and structural correlation of pKBH+ for meta- and para- substituted benzamides in sulfuric acid solutions [PDF]

Journal of the Serbian Chemical Society, 2006
The protonation of some meta and para substituted benzamides in sulfuric acid solutions was studied by UV spectroscopy in the 190–350 nm region. Principal component analysis was applied to separate the effect of protonation from the medium effect.
EMIL POPOVSKI, GORAN STOJKOVIC
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A Web Tool for Calculating Substituent Descriptors Compatible with Hammett Sigma Constants [PDF]

Chemistry–Methods, 2021
Electron donating or accepting power of organic substituents is an important parameter affecting many properties of parent molecules, most notably their reactivity and pKa of ionizable groups. These substituent properties are usually described by Hammett sigma constants obtained by measuring ionization of substituted benzoic acids.
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Microsomal superoxide anion production and NADPH-oxidation in a series of 22 aziridinylbenzoquinones [PDF]

, 1989
Several 2,5-bis(1-aziridinyl)-1,4-benzoquinones (BABQs) can be activated to alkylating species by reduction of the quinone moiety. On the other hand, cytotoxicity of these compounds can be induced by redox cycling.
Koster, Andries Sj., Prins, Bram, Reinhoudt, David N., Verboom, Willem   +3 more
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The Substituent Effect on the Radical Scavenging Activity of Apigenin

Molecules, 2018
Flavonoids widely found in natural foods are excellent free radical scavengers. The relationship between the substituent and antioxidative activity of flavonoids has not yet been completely elucidated. In this work, the antioxidative activity of apigenin
Yan-Zhen Zheng, Da-Fu Chen, Geng Deng, Rui Guo   +3 more
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Synthesis, IR and NMR spectral correlations in some symmetrical diimines

Bulletin of the Chemical Society of Ethiopia, 2014
A series of diimines have been synthesized by coupling of diamine with substituted benzaldehydes. The purities of these diimines were checked by their analytical and spectroscopic data. The spectral frequencies νCN (cm-1), NMR chemical shifts (δ, ppm) of
G. Thirunarayanan
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Catalytic and mechanistic studies into the epoxidation of styrenes using manganese complexes of structurally similar polyamine ligands [PDF]

, 2014
The synthesis and catalytic activity of manganese(ii) complexes of two polyamine ligands is reported which highlights how a small structural change in the ligand affects the overall catalytic behaviour.
Al-Safadi, R, De Faveri, G, Follier, T, Ilyashenko, G, Motevalli, M, Watkinson, M   +5 more
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The Alkaline Hydrolysis of Sulfonate Esters: Challenges in Interpreting Experimental and Theoretical Data [PDF]

, 2013
Sulfonate ester hydrolysis has been the subject of recent debate, with experimental evidence interpreted in terms of both stepwise and concerted mechanisms.
Adel O. Al Hussain, Aeberhard P. C., Alberts A., Alkherraz A., Babtie A. C., Baumann E., Becke A. D., Benkovic S. J., Blanch J. H., Camaioni D. M., Chai J.-D., Chipot C., Cleland W. W., Cohen A. J., Cohen A. J., Cossi M., Day P. N., Deacon T., Denis P. A., D’Rozario P., Edwards D. R., Farrar C. R., Fendler E. J., Fernanda Duarte, Friedman H. L., Frisch M. J., Gaël Marloie, González L., Gordon I. M., Hahn D. K., Hansch C., Hine J., Hopkins A., Hratchian H. P., Hratchian H. P., Hussein F. A., Im L. R., Jaffé H. H., Jensen J. H., Jensen R. A., Johnson E. R., Jonas S., Kamerlin S. C. L., Kamerlin S. C. L., Kamerlin S. C. L., Kamerlin S. C. L., Kertesz M. A., Khersonsky O., Kirby A. J., Klähn M., Korang J., Lassila J. K., Lee C., Lezina V. P., Li H., Lynch B. J., Lönnberg H., Marenich A. V., McWhirter C., Mohamed M. F., Nakata K., Nicholas H. Williams, Palascak M. W., Pliego J. R., Pliego J. R., Pregel M. J., Pregel M. J., Ribeiro A. J. M., Rosta E., Shina Caroline Lynn Kamerlin, Swart M., Takano Y., Thea S., Ting Geng, Tortonda F. R., Um I. H., Um I.-K., van der Ploeg J. R., van Loo B., Villà J., Vosko S. H., Williams A., Williams A., Williams A., Wolfenden R., Xie D., Yanai T., Young P. R., Younker J. M., Zalatan J. G., Zhan C. G., Zhang L., Zhao Y., Zhao Y., Zhu T.   +94 more
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