D , = 1.39; space group Pi-(assumed from racemic nature of synthetic product). c) Crystallized from methanolethyl acetate solution: monoclinic, a = 9.94, b = 21.12, c = 14.9 A, = 92"55', V = 3039 A3, D , = 1.32 (assuming 2 = 4), D , = 1.35; space group PZJn (2nd setting). d ) Crystallized from methanolethyl acetate solution: monoclinic, a = 11.62, b = 24.40, c = 10.50, y = 90"10', V = 2960 A3, D , = 1.35 (assuming 2 = 4), D , = 1.36, space group P Z J b (1st setting).
The modification d), which occurs as well-formed crystals, was chosen for the more detailed analysis described below. Crystals of the other three modifications are inferior to those of d), and the discrepancies between D , and D , suggest that they probably contain solvent of crystallization.
Cell dimensions are based on measurements on 30"-precession photographs and should be accurate to within about 0.2%.
Intensity Measurements.
-The layers hk0-hkll were measured out to a limit of sin0 = 0.42 from a crystal of dimensions 0.2 x 0.4 x 0.56 nim mounted on the Amdt-Phillifis linear diffractometer [4] in its commercially available version with MoKm radiation and Sr/Zr balanced filters. .%bout 5400 independent reflexions were measured, but the subsequent analysis was based exclusively on the 1329 reflexions with net intensity greater than four times the standard deviation of the measurement. The intensities were corrected for Loventz-poIarization effects, but not for absorption, to give the relative F2-values.