Molecular and Crystal Structure of (1R)-2-arylidene-p-(4-menthen)-3-ones

Abstract

The molecular structure of chloro-, methoxy-, and methoxyphenyl-substituted (1R)-arylidene-p-(4-menthen)-3-ones was studied by X-ray diffraction. The cyclohexenone ring in the compounds has a sofa conformation with a virtually planar geometry of the s-trans-enone fragment. Based on the experimental data and AM1 calculations it is shown that the electronic effects of substituents do not affect the conformational characteristics of the benzylidene-menthenone fragment, but change the bond lengths in the conjugate system. The endocyclic double bond in the molecules causes pronounced flattening of the exocyclic s-cis-enone and benzylidene groups compared to the corresponding derivatives of p-menthan-3-one. The structural peculiarities of the compound with a biphenylyl group are interpreted as the consequence of intermolecular interactions in crystal.