D. KANAGAPUSHPAM, V. RAMAMURTHY AND K. VENKATESAN 1131 approximations, this approach was successful in ration- alizing the rigid systems like coumarin derivatives (Murthy, Arjunan, Venkatesan & Ramamurthy, 1986). We have assumed in these calculations that the overall topography of the excited molecule is the same as in the ground state. This clearly is not true and this assump- tion is more serious in the present molecule than in rigid molecules such as coumarins. In its reaction pathway involving change in the hybridization of the reactive atoms C(9) and C(14) from sp 2 to sp 3 with a lengthy styrene side group at C(9), it would be expected that the side group undergoes considerable positional changes in the existing crystal lattice which might not be favour- able from the intermolecular energy calculations. It seems most likely that the available cavity volume (Cohen, 1975) is insufficient as the molecular topology undergoes very large changes in the course of the reaction path from the reactant to the product. We record our grateful thanks to Professor A. J. Birch, FRS, Australian Academy of Sciences, for suggesting this problem and Professor V. Ramakrish- nan for useful discussions. References ARIEL, S., ASKARI, S., SCHEFFER, J. R., TROTTER, J. & WALSH, L. (1984). J. Am. Chem. Soc. 106, 5726-5728. BHADBHADE, M. M., MURTHY, G. S., VENKATESAN, K. & RAMAMURTHV, V. (1984). Chem. Phys. Lett. 109, 259-263. BUSING, W. R. (1981). WMIN. A computer program to model molecules and crystals in terms of potential-energy functions. Report ORNL-5747. Oak Ridge National Laboratory, Ten- nessee. COHEN,M. D. (1975). Angew. Chem. Int. Ed. Engl. 14, 386-393. COHEN, M. D. & SCHMIDT,G. M. J. (1964). J. Chem. Soc. pp. 1996-1999. COHEN, M. D., SCHMIDT,G. M. J. & SONNTAG, F. J. (1964). J. Chem. Soc. pp. 2000-2013. GNANAGURU, K., RAMASUBBU, N., VENKATESAN, K. & RAMAMURTHY, V. (1985). J. Org. Chem. 50, 2337-2346. International Tables for X-ray Crystallography (1974). Vol. IV. Birmingham: Kynoch Press. (Present distributor D. Reidel, Dordrecht.) MAIN, P., FISKE, S. J., HULL, S. E., LESSINGER, L., GERMAIN, G., DECLERCQ, J.-P. & WOOLFSON, M. M. (1980). MULTAN80. A System of Computer Programs for the Automatic Solution of Crystal Structures from X-ray Diffraction Data. Univs. of York, England, and Louvain, Belgium. MIRSKY, K. (1978). In Computing in Crystallography, edited by H. SCHENK, R. OLITHOF-HAZEKAMP, H. VAN KONINGSVELD• G. C. BASSI, pp. 169-182. Delft Univ. Press. MURTHY, G. S., ARJUNAN, P., VENKATESAN,K. t~. RAMAMURTHY, V. (1986). Tetrahedron. In the press. NAKANISHI, H., PARKINSON, G. M., JONES, W., THOMAS, J. M. & HASEGAWA, M. (1979). Isr. J. Chem. 18, 261-265. RAMAMURTHV, V. & VENKATESAN, K. (1986). Chem. Rev. In the press. READ,J. & SMITH,H. G. (1921). J. Chem. Soc. 119, 779-789. READ,J. & SMITH,H. G. (1922). J. Chem. Soc. 121, 574-593. ROMERS, C., ALTONA,C., Buys, H. R. & HAVINGA, E. (1969). In Topics in Sterochemistry, Vol. 4, edited by E. L. ELIEL& N. L. ALLINGER, pp. 39--98. New York: John Wiley. SCHMIDT, G. M. J. (1964). J. Chem. Soc. pp. 2014-2021. SHELDRICK, G. M. (1976). SHELX76. Program for crystal structure determination. Univ. of Cambridge, England. Acta Cryst. (1987). C43, 1131-1134 Structure of 5-(p-Aminobenzenesulfonamido)-l-phenylpyrazole (Sulfaphenazole)* BY H. C. PATEL AND T. P. SINGH Department of Biophysics, All-India Institute of Medical Sciences, New Delhi - 110029, India (Received 25 August 1986; accepted 12 January 1987) Abstract. C~sH14N402S, Mr=314.4, monoclinic, P21/n, a = 14.760 (3), b = 11.253 (2), c= 19.213 (4) A, fl=109.90(3) ° , V=3001(1)A 3, Z=8, Dm= 1.397 (5), D x = 1.3916 (5) Mg m -3, 2(Mo Ktx) = 0.71069A, p=0.216mm -l, F(000)=1312, T= 293 K, final R = 0.067 for 3208 observed reflections. The two crystallographically independent molecules A and B in the structure have similar molecular dimen- sions but their conformations are substantially different. *Chemical Abstracts name: 4-amino-N-(1-phenyl-lH-pyrazol- 5-yl)benzenesulfonamide. 0108-2701/87/061131-04501.50 The six-membered benzene-ring planes in molecule A and in molecule B are inclined to the planar pyrazole rings at 53.5 (4) and 46.9 (4)°; 75.9 (3) and 69.1 (4) ° respectively. The two benzene-ring planes in molecule A are mutually inclined at 12.8 (3) ° while those in molecule B are oriented at 36.5 (4) °. Both molecules show gauche conformations about the S--N bonds with torsion angles of-73.7 (8) and 94.0 (8) ° respectively. The molecules are packed in the form of hydrogen- bonded helices which are interconnected by hydrogen bonds and van der Waals forces through the amino N atoms and the sulfonyl O atoms. © 1987 International Union of Crystallography