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Barriers to internal rotation in neopentylbenzenes substituted on the benzyl group. A 13 C NMR band shape study
Author(s) -
Andersson Sven,
Drakenberg Torbjörn
Publication year - 1983
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/omr.1270211206
Subject(s) - substituent , internal rotation , chemistry , group (periodic table) , carbon 13 nmr , crystallography , rotation (mathematics) , chemical shift , stereochemistry , organic chemistry , geometry , mathematics , mechanical engineering , engineering
Two series of neopentylbenzenes with one or two substituents on the benzyl group have been synthesized. In one series the substituents were H, F, Cl, Br, I, OCH 3 , OCOCH 3 , OSi(CH 3 ) 3 CH 3 and CH 2 CH 3 , and in the other OH and R [R H, CH 3 , CH 2 CH 3 , (CH 2 ) 3 CH 3 , CH(CH 3 ) 2 and C(CH 3 ) 3 ]. Barriers to internal C sp 3C sp 2 (aryl)and C sp 3C sp 3rotation have been estimated by 13 C NMR band shape methods. Estimated barriers were found to increase as the size of the substituent increases. The results are discussed in terms of possible initial and transition states, based on summations of results from molecular mechanics (MM) calculations, using the Allinger MMP1 program. Barriers estimated experimentally are compared with results from other systems found in the literature.