Molecular Structure of 1-Substituted Bicyclo[2.2.0]hexanes: A Combined X-Ray Structural and Ab Initio Study

The synthesis and X-ray crystal structure of the p-bromoanilide derivative of bicyclo2.2.0]hexane-l-carboxylic acid (1), N-(4-bromophenyl)-bicyclo2.2.0]hexane-l-carboxamide (2), is reported. N-(4-Bromophenyl)-bicyclo2.2.0]hexane-l-carboxamide is synthesized in good yield via the DCC coupling of bicyclo2.2.0]hexane-l-carboxylic acid (1) with p-bromoaniline. Low-temperature X-ray analysis of 2 reveals that the bonds of the bicyclo2.2.0]hexane skeleton vicinal to the amide group show a slight lengthening due to conjugative interaction with the -accepting amide group. Ab initio calculations at the 6-31G* level of theory on bicyclo2.2.0]hexane-l-carboxamide, a model for 2, and for other 1-substituted bicyclo2.2.0]hexanes are also reported.