Results 151 to 160 of about 5,651,932 (190)
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A relationship between dipole moments and the Hammett equation
Recueil des Travaux Chimiques des Pays-Bas, 1957AbstractAn empirical formula is proposed relating the constant ω in the Hammett equation to the observed dipole moment of a compound (para‐ or meta‐ C6H4XY). This relationship is checked by using data which have been cited in the literature. These data appear to confirm the proposed linear behaviour when log μ is plotted against σ.
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1,2-Diaryl-2-imidazolines. A structure–basicity relationship: application of the Hammett equation
J. Chem. Soc., Perkin Trans. 2, 1973The pKa values of sixteen 1,2-diaryl-2-imidazolines have been determined and the influence of substituents at N-1 and C-2 upon basicity have been studied. The experimental data have been successfully correlated with the Hammett equation, the imidazoline ring being considered a substituent of the benzene ring.
B. Fernández, I. Perillo, S. Lamdan
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Quantitative structure–retention relationships of phenolic compounds without Hammett’s equations
Journal of Chromatography A, 2003Retention times of phenolic compounds in a given pH eluent in reversed-phase liquid chromatography were predicted from dissociation constants derived from atomic partial charges and log P-values calculated by a computational chemical method. The precision of the calculation of atomic partial charges by AMI and PM3 methods of MOPAC was evaluated.
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Advanced Materials, 2020
AbstractWhile the unique physicochemical properties of nanomaterials that enable regulation of nanozyme activities are demonstrated in many systems, quantitative relationships between the nanomaterials structure and their enzymatic activities remain poorly understood, due to the heterogeneity of compositions and active sites in these nanomaterials ...
Jiangjiexing Wu +10 more
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AbstractWhile the unique physicochemical properties of nanomaterials that enable regulation of nanozyme activities are demonstrated in many systems, quantitative relationships between the nanomaterials structure and their enzymatic activities remain poorly understood, due to the heterogeneity of compositions and active sites in these nanomaterials ...
Jiangjiexing Wu +10 more
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The Journal of Physical Chemistry A, 2005
Density functional theory has been applied to describe electronic substituent effects, especially in the pursuit of linear relationships similar to those observed from physical organic chemistry experiments. In particular, analogues for the Hammett equation parameters (sigma, rho) have been developed.
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Density functional theory has been applied to describe electronic substituent effects, especially in the pursuit of linear relationships similar to those observed from physical organic chemistry experiments. In particular, analogues for the Hammett equation parameters (sigma, rho) have been developed.
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Tetrahedron Letters, 1981
Abstract A nonlinear Hammett relationship could be used as evidence for a change-over in mechanism in the alkaline hydrolysis of methyl carbanilates. The electron-withdrawing substituted compounds hydrolyse via an A–E pathway (ϱ 1.06) whereas the hydrolysis of the electron-donating substituted compounds involves an E-A scheme.
Michel Bergon, Jean-Pierre Calmon
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Abstract A nonlinear Hammett relationship could be used as evidence for a change-over in mechanism in the alkaline hydrolysis of methyl carbanilates. The electron-withdrawing substituted compounds hydrolyse via an A–E pathway (ϱ 1.06) whereas the hydrolysis of the electron-donating substituted compounds involves an E-A scheme.
Michel Bergon, Jean-Pierre Calmon
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Canadian Journal of Chemistry, 1971
Exact thermodynamic analysis of the Hammett equation has led to four differential equations relating δΔH0, δΔS0, δΔCp0, dρ/dT, and d2ρ/dT2. Similar equations can be obtained in terms of activation parameters ΔH≠, etc. For temperature independent δΔH0 and δΔS0 and therefore δΔCp0 = 0, two of these differential equations lead to ρ = ρ∞ [1–(β1/T)] and ...
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Exact thermodynamic analysis of the Hammett equation has led to four differential equations relating δΔH0, δΔS0, δΔCp0, dρ/dT, and d2ρ/dT2. Similar equations can be obtained in terms of activation parameters ΔH≠, etc. For temperature independent δΔH0 and δΔS0 and therefore δΔCp0 = 0, two of these differential equations lead to ρ = ρ∞ [1–(β1/T)] and ...
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International Journal of Quantum Chemistry, 2012
AbstractLocal reactivity is obtained for isatoic anhydride (ISA) (2H 3,1‐benzoxazin‐2,4(1H)‐dione) and 20 of its derivatives, using reactivity indices such as: local softness, condensed Fukui function, relative electrophilicity index, and relative nucleophilicity index.
José S. Durand‐Niconoff +4 more
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AbstractLocal reactivity is obtained for isatoic anhydride (ISA) (2H 3,1‐benzoxazin‐2,4(1H)‐dione) and 20 of its derivatives, using reactivity indices such as: local softness, condensed Fukui function, relative electrophilicity index, and relative nucleophilicity index.
José S. Durand‐Niconoff +4 more
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Analytical Chemistry, 1997
Substituted 1,2-diphenylethanes undergo competitive dissociations upon electron ionization (EI) to generate substituted benzyl cation and benzyl radical pairs. Application of the kinetic method to the previous reported EI mass spectra of these covalently bound precursor ions (data are taken from McLafferty et al. J. Am. Chem. Soc.
G, Chen, P, Wong, R G, Cooks
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Substituted 1,2-diphenylethanes undergo competitive dissociations upon electron ionization (EI) to generate substituted benzyl cation and benzyl radical pairs. Application of the kinetic method to the previous reported EI mass spectra of these covalently bound precursor ions (data are taken from McLafferty et al. J. Am. Chem. Soc.
G, Chen, P, Wong, R G, Cooks
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The hammett relationship in CpTiCl2OPhX (X = CH3O, CH3, Cl, NO2) + BuLi(Et2AlCl) catalytic systems
Journal of Organometallic Chemistry, 1985Abstract The CpTiCl2OPhX (X = CH3O, CH3, Cl, NO2 + BuLi system is active m olefin hydrogenation, while the CpTiCl2OPhX + Et2AlCl system is active in olefin polymerization. In both cases a linear relationship between the Hammett substituent constants and the catalytic activity of the investigated systems is found.
W. Skupiński, A. Wasilewski
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