Results 121 to 130 of about 2,266 (161)
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Relationship between the electrophilicity and σp Hammett constant in Baeyer–Villiger reactions
Chemical Physics Letters, 2008Abstract The Baeyer–Villiger oxidation of some aldehydes and ketones has been revised by using the electrophilicity as a descriptor of reactivity. The global electrophilicity index evaluated at the ground state of a series of aromatic aldehydes and ketones shows a linear relationship with the σ p Hammett substituent constants.
Meneses, L. +3 more
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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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Australian Journal of Chemistry, 1985
It is shown that the temperature-dependence of the Hammett equation is, in contrast to tradition, both physically and experimentally better described by means of temperature-dependent s and temperature- independent ? (termed ?o). The relationship between ?o and the customary (temperature dependent) ?
W Linert, R Schmid, AB Kudrjawtsev
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It is shown that the temperature-dependence of the Hammett equation is, in contrast to tradition, both physically and experimentally better described by means of temperature-dependent s and temperature- independent ? (termed ?o). The relationship between ?o and the customary (temperature dependent) ?
W Linert, R Schmid, AB Kudrjawtsev
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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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Macromolecules, 1999
In this work, pulsed laser polymerization measurements of the homopropagation rate coefficients (k(p)) for a series of para-substituted styrene monomers ( 4-X-styrene: X = OCH3, CH3, F, Cl, Br) at 20, 30, and 40 degrees C are reported. On the basis of nonlinear least-squares fits of the Arrhenius model to these data, the following point estimates for ...
Coote, ML, Davis, TP
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In this work, pulsed laser polymerization measurements of the homopropagation rate coefficients (k(p)) for a series of para-substituted styrene monomers ( 4-X-styrene: X = OCH3, CH3, F, Cl, Br) at 20, 30, and 40 degrees C are reported. On the basis of nonlinear least-squares fits of the Arrhenius model to these data, the following point estimates for ...
Coote, ML, Davis, TP
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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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