Crystal and molecular structure of 1,3-diphenyl-4-p-chlorobenzal-5-pyrazolone

Crystals of 1,3-diphenyl-4-p-chlorobenzal-5-pyrazolone, C₂₂H₁₅ClNN₂O, are triclinic:a = 13.96,b = 12.94,c = 7.29 Å, = 93.0 ° = 100.1 °, = 135.6 °,Z = 2, space groupP¯1. The structure has been determined from Weissenberg X-ray data by direct methods, and refined by full-matrix least squares toR = 0.098 for 1949 observed reflexions. The molecular conformation of the double bond at chlorobenzal is of type Z. The phenyl rings make angles of 9.2 ° and 47.7 ° and thep-chlorophenyl group an angle of 4.2 ° all with the plane of the pyrazolone moiety, thus allowing extended conjugation. Comparisons of bond distances and angles with those of similar molecules are made. Close molecular packing is afforded by layers of molecules approximately parallel to (¯110).