research papers 112 Olivato et al.  -(p-Phenylsulfinyl)-p-substituted acetophenones Acta Cryst. (2000). B56, 112±117 Acta Crystallographica Section B Structural Science ISSN 0108-7681 Preferred conformations in the solid state of some a-(p-phenylsulfinyl)-p-substituted acetophenones Paulo R. Olivato, a * Sandra A. Guerrero a and J. Zukerman- Schpector a,b a Instituto de Quõ Âmica, Universidade de Sa Äo Paulo, CP 26077, CEP 05599-970, Sa Äo Paulo, SP, Brazil, and b Laborato  rio de Cristalografia Estereodina Ãmica e Modelagem Molecular, DQ- UFSCar, CP 676, CEP 13565-905, Sa Äo Carlos, SP, Brazil Correspondence e-mail: prolivat@iq.usp.br # 2000 International Union of Crystallography Printed in Great Britain ± all rights reserved Information on the geometrical structures of -(p-phenylsul- ®nyl)-p-substituted acetophenones XÐPhC(O)CH 2 S(O)PhÐ Y [X = OMe, Y = H (1); X = NO 2 , Y = OMe (2); X = OMe, Y = NO 2 (3); IUPAC names: (1) 4-methoxyphenyl phenylsul®nyl- methyl ketone; (2) 4-nitrophenyl 4-methoxyphenylsul®nyl- methyl ketone; (3) 4-methoxyphenyl 4-nitrophenyl- sul®nylmethyl ketone] have been obtained from X-ray diffraction analyses. A comparison of these results with those previously obtained from X-ray diffraction and ab initio computations of -methylsul®nylacetophenone, PhC(O)CH 2 - S(O)Me, indicated that (1) and (2) adopt in the crystal a cis 1 conformation and (3) assumes a quasi-gauche geometry. The stabilization of these conformations in the crystal is discussed in terms of the dipole moment coupling, Coulombic and intramolecular charge transfer interactions between the oppositely charged atoms of the C O and S O dipoles. The p-substituted benzene ring is quasi-coplanar with the sul®nyl group for (1) and (3), but is quasi-perpendicular for (2). Conjugation and repulsion between the sul®nyl sulfur lone pair and the -benzene ring seem to be responsible for the observed geometries. Received 13 May 1999 Accepted 24 June 1999 1. Introduction Our previous IR and X-ray diffraction studies supported by 6- 31G ** ab initio calculations of some -alkylsul®nylacetophe- nones (Olivato et al. , 1998; Distefano et al. , 1996), PhC(O)CH 2 S(O)R (R = Me, Et and Bu t ), have shown that these compounds adopt a cis 1 conformation in the solid state, for which the O atoms of the S O and C O dipoles are close to each other. The stabilization of the cis 1 conformation in the crystal has been ascribed to dipole moment coupling along with Coulombic attraction, and intramolecular charge transfer between the negatively charged carbonyl O atom and the positively charged sul®nyl S atom [O  (CO)S + (SO)], which should overcome the repulsive ®eld effect between C O and S O dipoles. In order to further investigate the nature of the electronic and Coulombic interactions which occur in the solid state of - sul®nylacetophenones the present paper reports the X-ray structures of some -(p-phenylsul®nyl)-p-substituted aceto- phenones (I): X = OMe and Y = H for (1); X = NO 2 , Y = OMe for (2) and X = OMe, Y = NO 2 for (3).