Crystal and molecular structure of the p-chloroanilide derivative of bicyclo[5,3,1]undec-7-en-11-one-1-carboxylic acid

Abstract

The structure of the p-chloroanilide derivative of bicyclo[5,3,1]undec-7-en-11-one-1-carboxylic acid (I, R =p-ClC₆H₄·NH·CO) has been determined by a single-crystal X-ray analysis. The crystals are orthorhombic, space group Pbcn, with Z= 8 in a unit cell of dimensions a= 19·97, b= 7·67, and c= 21·35 Å. The structure was solved by the heavy-atom method and refined by least-squares calculations to R= 0·092 for 983 independent reflexions. The bridgehead position of the double bond produces molecular strain which not only results in distortion of the double bond itself, but also results in a molecular conformation in which there is incomplete delocalisation of the π-electrons in the enone system. This is reflected by abnormal spectroscopic and chemical properties for the compound (I, R = H and R = CO₂Et) which may be correlated with the molecular geometry determined by the structure analysis.