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Relative rates of bromination and chlorination of 4‐substituted cyclopentenes in methanol, ethanol and acetic acid
Author(s) -
Zhang BenLi,
Qiu Jian,
Gao ZhenHeng
Publication year - 1989
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610020104
Subject(s) - chemistry , halogenation , acetic acid , steric effects , methanol , ethanol , medicinal chemistry , alcohol , organic chemistry
A set of 4‐monosubstituted cyclopentenes, , were synthesized and their relative rates ( k X / k H ) for bromination and chlorination were determined in methanol, ethanol and acetic acid at 25 °C by competitive method. log( k X / k H ) for most of the substituents can be correlated by means of Taft's equation, log( k X / k H ) = ρ I σ I + C . In methanol ρ I, Br 2= −2·91, ρ I, Cl 2= −0·49, in ethanol ρ I, Br 2= −3·07, ρ I, Cl 2= −0·70 and in acetic acid ρ I, Br 2= −1·64, ρ I, Cl 2= −0·65. The presence of C(<0) is due to a constant steric effect. The deviation of X = H is ascribed to the absence of the steric effect and that of X = CO 2 Me and CO 2 Et is accounted for in terms of anchimeric assistance. For chlorination no anchimeric assistance was observed.