Effect of bulk groups substitution on conformational behavior and structure of gauche-gauche cyclopropylmethanol

The structure of cyclopropylmethanol in the gauche-gauche conformation was reinvestigated by utilizing the rotational constants of the parent and three deuterated species obtained from a previous microwave study, and a better fit of the observed rotational constants was determined with torsional angles of -53° and 123° respectively for the hydrogen and oxygen atoms of the hydroxyl group. The dipole moments and rotational constants measured by microwave data were clearly found to be consistent with those predicted by ab initio calculations only for the gauche-gauche conformer of cyclopropylmethanol. The conformational stability of 1-methylcyclo-propylmethanol, 1-fluorocyclopropylmethanol and 1-chlorocyclopropylmethanol were investigated by ab initio methods and the relative stability of the gauche-gauche conformer was predicted to increase in the case of 1-methylcyclopropylmethanol and to decrease in the case of the halo derivatives.