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1H and 13C NMR study of hindered rotation in N1,N1-dimethyl-N2-substituted phenylacetamidines

✍ Scribed by Iwona Wawer

Publisher: John Wiley and Sons
Year: 1988
Tongue: English
Weight: 636 KB
Volume: 26
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1260260713

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✦ Synopsis

Bamers to rotation about the partial double C-N' bond were determined from line shape analysis of 'H and I3C dynamic NMR spectra of N',N'-dimethyl-NZ-substituted phenylacetamidines with twelve different substituents on the phenyl ring. The values of AGGc are 51.2-58.7 kJ mol-' and the correlation with Hammett's u values indicates an important contribution from the substituent effects to the barrier height. The decrease of the rotational barrier of approximately 10 kJ mol-' in acetamidines in comparison with the respective formamidines is probably mainly due to a steric interaction of the C-CH, group with aromatic protons; this leads to non-planarity and a decrease of the conjugation of the aromatic ring with the acetamidine moiety. KEY WORDS 'H and 13C NMR Rotation barriers N',N'-Dimethyl-NZ-substituted phenylacetamidines

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