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-carbony l sulfones, XC(O)CH(2)SO(2)R (1-10, X = Et(2)N, EtS, EtO, alkyl, and a ryl, and R' = alkyl, and aryl), are obtained for different pairs of th e X and R substituents. The results of the X-ray diffraction and of th e PE spectral analyses fully agree with the results of optimized ab in itio 3-21G calculations. The electron charge distribution at various atoms and/or groups is discussed in connection with the other observab les. 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 soli d phase. This conformation is dictated by the interplay of the electro nic interactions between the XC(O) and SO(2)R groups with two strong n onbonded interactions between pairs of oppositely charged atoms. The n egatively charged carbonyl oxygen and one of the sulfonyl oxygen atoms Lie at distances shorter than the sum of the corresponding van der Wa als radii from the positively charged sulfur and carbonyl carbon atoms , respectively. The interaction of the sulfonyl oxygen with the carbon yl carbon atom is the stronger of the two and partially offsets the st rong inductive effect of the sulfonyl group. The presence of both thro ugh-bond and through-space interactions between the carbonyl and the s ulfonyl groups in the ground and ionized states is confirmed by eigenv ector analysis and by the shifts in the MO energies with respect to th ose of reference compounds. The conformation of compound 5, in the sol id phase, is in part determined by crystal packing forces.