Barrier to Internal Rotation in 1,2-Bis(bromochloromethyI)-3,4,5,6-tetraisopropyl-benzene

Silvio E. Biali, Kurt Mislow

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8 Scopus citations

Abstract

The tightly gear meshed arrangement of isopropyl and dichloromethyl groups in hexaisopropyl- and hexakis(di-chloromethyl)benzene, respectively, imparts a high barrier to internal rotation. For hexaisopropylbenzene,1 a lower limit of 22 kcal mol-1 was estimated for the topomerization barrier from NMR measurements on a d28 isotopomer and a barrier of ca. 35 kcal mol-1 was calculated by use of the empirical force field (EFF) method. For hexakis(di-chloromethyl) benzene,2 the calculated (EFF) topomerization barrier was 33.9 kcal mol-1. Consistent with these findings is the lower limit of 24 kcal mol?1 estimated (NMR) for the enantiomerization barrier in (1′RS,2′SR)-1,2-bis(l-bromoethyl)-3,4,5,6-tetraisopropyl-benzene.3.

Original languageAmerican English
Pages (from-to)1318-1320
Number of pages3
JournalJournal of Organic Chemistry
Volume53
Issue number6
DOIs
StatePublished - 1 Mar 1988
Externally publishedYes

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