X-RAY-DIFFRACTION, UV PHOTOELECTRON, AND AB-INITIO STUDY OF INTRAMOLECULAR INTERACTIONS IN BETA-CARBONYL SULFONES

Information on the geometric and electronic structures of beta-carbonyl sulfones, XC(O)CH(2)SO(2)R (1-10, X = Et(2)N, EtS, EtO, alkyl, and aryl, and R' = alkyl, and aryl), are obtained for different pairs of the X and R substituents. The results of the X-ray diffraction and of the PE spectral analyses fully agree with the results of optimized ab initio 3-21G* calculations. The electron charge distribution at various atoms and/or groups is discussed in connection with the other observables. In the compounds studied the CH2-S bond is gauche to the carbonyl group irrespective of the X and R substituents and of the gas or solid phase. This conformation is dictated by the interplay of the electronic interactions between the XC(O) and SO(2)R groups with two strong nonbonded interactions between pairs of oppositely charged atoms. The negatively charged carbonyl oxygen and one of the sulfonyl oxygen atoms Lie at distances shorter than the sum of the corresponding van der Waals radii from the positively charged sulfur and carbonyl carbon atoms, respectively. The interaction of the sulfonyl oxygen with the carbonyl carbon atom is the stronger of the two and partially offsets the strong inductive effect of the sulfonyl group. The presence of both through-bond and through-space interactions between the carbonyl and the sulfonyl groups in the ground and ionized states is confirmed by eigenvector analysis and by the shifts in the MO energies with respect to those of reference compounds. The conformation of compound 5, in the solid phase, is in part determined by crystal packing forces.