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Influence of the 1,1,3,3‐tetramethylguanidinyl substituent on the charge distribution in chlorobenzenes, studied by 35 Cl NQR
Author(s) -
Nogaj Boleslaw,
Pruszyński Przemyslaw
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250405
Subject(s) - chemistry , substituent , chlorobenzene , steric effects , resonance (particle physics) , inductive effect , stereochemistry , organic chemistry , atomic physics , physics , catalysis
35 Cl NQR measurements were carried out on a series of chlorobenzenes with the 1,1,3,3‐tetramethylguanidinyl substituent {TMG = –N=C[N(CH 3 ) 2 ] 2 }. The substituent constants σ p , σ m , σa I , and σ R for the TMG group were estimated from the relationships between the NQR resonance frequencies, ν Q , and substituent constant values, σ. The ν Q value for 2‐(4‐chlorophenyl)‐1,1,3,3‐tetramethylguanidine is the lowest observed for all chlorobenzenes, and arises from the strong positive conjugative effect of the TMG group. This effect is attributed to the possible resonance stabilization of the positive charge. Steric inhibition of resonance is observed for the ortho‐substituted isomers .