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Barriers to internal rotation in 1,3,5‐trineopentylbenzenes: 10 — 13 C and 19 F NMR band shape studies and force field calculations
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.1270211004
Subject(s) - internal rotation , chemistry , aryl , force field (fiction) , carbon 13 nmr , computational chemistry , crystallography , stereochemistry , physics , organic chemistry , alkyl , mechanical engineering , quantum mechanics , engineering
1,3,5‐Trineopentylbenzenes (TNB) with one or two benzylic substituents in each neopentyl group were synthesized. The substituents were F, Cl, Br, J, OCH 3 , OCOCH 3 , OSi(CH 3 ) 3 and CH 3 and, in cases of disubstitution, F, Cl, Br, CH 3 and Cl, CH 3 and Br and SCH 2 CH 2 S. Barriers to internal C sp3 C sp2 (aryl) and C sp3 C sp3 rotation were estimated by 13 C and 19 F NMR band shape methods. Estimated barriers in the TNB series were found to be very close to those found for the corresponding mononeopentylbenzenes. For some of the compounds studied, molecular mechanics (MM) calculations were performed with the Allinger MMP1 program. Differences between calculated and experimental estimated barriers were found, and possible sources of these discrepancies in terms of parameters used in the MMP1 program are discussed.