Restricted Rotation Involving the Tetrahedral Carbon. XLV. Appearance of a Maximum in the Rotational Barriers of 9-(1,1-Dimethyl-2-phenylethyl)triptycenes at a Medium-sized peri-Substituent

1 January 1983

journal article
research article
Published by Oxford University Press (OUP) in Bulletin of the Chemical Society of Japan

Vol. 56 (1) , 306-313
https://doi.org/10.1246/bcsj.56.306

Abstract

Rotational isomers of seven peri-substituted 9-(1,1-dimethyl-2-phenylethyl)triptycene derivatives were stereoselectively synthesized and classical kinetics on rotational isomerization were studied. While compounds with relatively small peri-substituents (F and OCH₃) showed higher barriers than the peri-unsubstituted one, the peri-chloro compound had almost the same barrier with and those carrying bulkier peri-substituents (Br, CH₃, and CF₃) showed lower barriers than the peri-unsubstituted one. These apparently anomalous phenomena may be explained in terms of large molecular deformation of these highly congested compounds.

Keywords

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