Results 221 to 230 of about 56,095 (275)

The ?* constants of ionic substituents

Bulletin of the Academy of Sciences of the USSR Division of Chemical Science, 1976
1. We determined the chemical shifts in the31P NMR spectra of the compounds\((C_2 H_5 O)_2 P(O)SX (X = (CH_2 )_m \mathop S\limits^ + (CH_3 )C_2 H_5 \), (CH2)mSC2H5 (m=2–4 and 6)) and CnH2n+1 (n=6, 8), and obtained a linear correlation between δp and the σ* constants of the X substituents. 2.
Ya. L. Yarv, T. I. Pekhk, A. A. Aaviksaar, D. I. Lobanov, N. N. Godovikov   +4 more
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Electrophilic Substituent Constant σ⁺ of Electron Donor Substituents in Nonpolar Media

The Journal of Organic Chemistry, 2009
The electrophilic substituent constant sigma(+) was derived from the relative rate constants of the solvolysis of substituted alpha-cumyl chlorides in an acetone/water solvent mixture in the original work by Brown and Okamoto (J. Am. Chem. Soc. 1958, 80, 4979).
Alexander, Oehlke, Alexander A, Auer, Katja, Schreiter, Katja, Hofmann, Franziska, Riedel, Stefan, Spange   +5 more
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Replacement Substituent Constants for Simple Heterocycles

Tetrahedron, 1989
Abstract 13 C nmr absorptions are reported for the β-vinylic carbon atoms in 15 series of ethylenes bearing heterocyclic substituents. The data are used to establish the best single-parameter substituent constants, σ 13 , for the various heterocycles as replacements for para -substituted benzenes.
Charles N. Robinson, Leonard J. Wiseman, Carl D. Slater   +2 more
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Correlations of coupling constants with alkyl substituent constants

Spectrochimica Acta Part A: Molecular Spectroscopy, 1986
Abstract The one-bond coupling constants ( 1 J XY ) of nine series of organometallic compounds with the part structure R-X-Y (R is an alkyl group attached directly to the metal atom X) have been correlated with two sets of alkyl substituent constants, TAFT's σ* and our σ a .
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NMR Substituent constants in alkylbenzenes

Recueil des Travaux Chimiques des Pays-Bas, 1967
AbstractThe substituent constants of alkyl groups in alkylbenzenes have been determined for dilute solutions in carbon tetrachloride. Especially for compounds with isolated substituents the constants derived satisfactorily correlate the chemical shifts of the ring protons with the substitution type.
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Substituent effects on tautomerisation constants of alkylaryltriazenes

Journal of the Chemical Society, Perkin Transactions 2, 1982
Both tautomers of propyl-p-nitrophenyl-, -p-cyanophenyl-, -3,5-dichlorophenyl-, -3,4-dichlorophenyl-, and -p-chlorophenyl-triazenes are directly observable by 1H n.m.r. at 200 MHz in CD3CN at 25 °C. In addition, lower temperature studies enable the two tautomers of propyl-p-methylphenyl- and-p-methoxyphenyl-triazenes to be quantitated.
Migel A. Kelly, Martin Murray, Michael L. Sinnott   +2 more
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Principal component analysis of substituent constants

Collection of Czechoslovak Chemical Communications, 1990
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.
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Chemometric Analysis of Substituent Effects. VII. Inductive Effect as a Basic Substituent Effect. Isoeffect Substituent Constant

Collection of Czechoslovak Chemical Communications, 1995
The paper deals with chemometric analysis of the inductive effect. The notion of inductive effect is discussed, and unambiguous definitions are given for the notions of triad: reaction centre-basic skeleton-substituent, and the therewith connected definitions of inductive effect.
Oldřich Pytela, Aleš Halama
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Determining the excited‐state substituent constants of meta‐substituent from 3,4'‐disubstituted stilbenes

Journal of Physical Organic Chemistry, 2012
In this paper, 61 samples of 3,4'‐disubstituted stilbenes and 18 samples of 3,3'‐disubstituted stilbenes were synthesized, and their UV data were measured in anhydrous ethanol. Based on the UV absorption energy (wavenumber) of 3,4'‐disubstituted stilbenes, the excited‐state substituent constants of meta‐substituent were determined by means of curve ...
Chenzhong Cao, Bin Sheng, Guanfan Chen
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Determining the excited‐state substituent constants of ortho‐substituents from 2,4’‐disubstituted stilbenes

Journal of Physical Organic Chemistry, 2019
AbstractThere are mainly three kinds of substituent electronic effects derived from aromatic rings: ground‐state, radical‐state, and excited‐state effect. However, excited‐state substituent constants of ortho‐substituents have not been reported up to now.
Chao‐Tun Cao, Hua Yuan, Qian Zhu, Chenzhong Cao   +3 more
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