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13 C nuclear magnetic resonance studies on acetophenones: Barriers to internal rotation
Author(s) -
Drakenberg Torbjörn,
Sommer Jean M.,
Jost Roland
Publication year - 1976
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.1270081110
Subject(s) - acetophenone , steric effects , internal rotation , substituent , chemistry , resonance (particle physics) , rotation (mathematics) , carbon 13 , rectangular potential barrier , nuclear magnetic resonance , crystallography , computational chemistry , stereochemistry , atomic physics , organic chemistry , physics , condensed matter physics , nuclear physics , catalysis , mechanical engineering , geometry , mathematics , engineering
Abstract The barrier to internal rotation in a series of p ‐substituted acetophenones has been determined by means of low temperature carbon‐13 n.m.r. and total bandshape analysis, resulting in: Δ G 140 ≠= 5·4 ± 0·1 kcal mol −1 (22·4 ± 0·4 kJ mol −1 ) for the unsubstituted acetophenone. The substituent effects on the barrier are found to be the same as for the corresponding benzaldehydes. The barrier height is discussed in terms of contributions from resonance and steric effects.