Conglomerate crystallization in organic compounds II. The conformation, configuration, and spontaneous resolution of 1-phenyl-2-cyano-cyclopropane

Abstract

The crystal structure of 1 -phenyi-2-cyano-cyclopropane was investigated to probe the stereochemical effects of placing different groups at the 2-position of the phenylcyclopropane moiety. The substance crystallized in space group P212121 with cell constants a=16.921(3), b=7.699(2), and c=6.251(2) A; V=814.33 A3 and D (calc; z=4) =1.168 g·cm−3. Final R(F)=0.04, using unit weights. The phenyl substituent is almost exactly in the bi-secting conformation with respect to the C-C-C angle at the point of attachment to cyclopropane. The average value of the C-C distances in the three-membered ring is 1.501 A, which is on the low side of the ranges cited in previous studies. When we apply the “additivity principle” to our measured geometrical data and calculate the “asymmetry parameters, ” the value ofδcns [0.012(3)] is a little low, but within experimental error it is in accord with the value (0.017) given by Allen. However, our value of δcns (0.006(3)] is substantially lower than Allen's, which is surprising, since the bisecting phenyl ring can exert its maximum effect on the asymmetry of cyclopropane. The substance undergoes spontaneous resolution into a conglomerate of chiral crystals. Unfortunately, in the absence of anomalous scatterers, the absolute configuration could not be determined; nonetheless, the space group in which the compound crystallizes is P212121, which leaves no ambiguity to the fact that the crystals are a conglomerate.