Premium
13 C NMR of substituted aryl carbenium ions: Continuous dependence of the ipso substituent shifts upon the carbenium character. Use of proportionality relationships for the evaluation of substituent–substituent interactions
Author(s) -
Membrey François,
Ancian Bernard,
Doucet JeanPierre
Publication year - 1978
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270111111
Subject(s) - substituent , chemistry , carbenium ion , ion , additive function , chemical shift , aryl , stereochemistry , computational chemistry , crystallography , mathematics , organic chemistry , mathematical analysis , alkyl
13 C substituent shifts in para ‐substituted phenyl and 2‐phenylethenyl carbenium ions have been studied within the general model of para ‐disubstituted benzenes XC 6 H 4 Y. Large variations are observed for the ipso shifts induced by the Y substituents (Y = NO 2 . … OCH 3 ) depending upon the electron demand at the remote carbenium centre. A good representation of these substituent‐substituent interactions is obtained by a treatment derived from ‘proportionality relationships’, where the deviations from strict additivity are factorized into two terms characterizing, respectively, the influence of the fixed X group on the ring and the susceptibility of the incoming Y substituent. Continuity of the ipso shift variations in an extended range is demonstrated, without break‐off between neutral polarized systems or ions as the electronic influence of the fixed X group increases.