Optical induction in chiral crystals. I. The crystal and molecular structures of 4,4'-dimethylchalcone

Abstract

The structure of 4,4'-dimethylchalcone (4,4'-dimethylbenzylideneacetophenone, C17H160) has been determined from three-dimensional diffractometer data by direct methods. The crystals are orthorhombic, space group P212,2~, with a= 15.2464, b=5.9059, e=14.6283 A,, Z=4. The structure was refined by least-squares calculations to R= 0.045. The molecule is distorted from planarity, the angle between the planes of the two phenyl rings being 48.6 °. This molecular conformation is believed to control the formation of an optically active product in the bromination reaction of a single crystal of the title compound.

16-(p-Butoxybenzylidene)androsta-1,4-diene-3,17-dione

“…These features of the styryl ketone fragment geometry of the title compound are essentially the same as those of chalcones (Rabinovich & Shakked, 1974;Rabinovich, Schmidt & Shakked, 1973) and 2-benzyl-5-benzylidenecyclopentanones (Theocharis, Nakanishi & Jones, 1981).…”

Stereoselective photodimerisation of chalcones in the molten state

“…This is very reasonable, because the C᎐ ᎐ C contact in the compound 1e crystal is too long (5.9 Å) to react. 13 The chiral arrangement of compound 1e molecules in the crystal was easily detected by measurement of CD spectra (Fig. 4) in Nujol mull.…”

“…3). Chiral order of 4,4Ј-dimethylchalcone molecules 1e 13 in their crystal state has been elucidated by X-ray analysis. 13 Enantioselective bromine addition to the chiral crystal of compound 1e which gives the optically active bromine addition product in low optical yield has also been reported.…”

Least-squares absolute-structure refinement. Practical experience and ancillary calculations

“…Rabinovich & Hope (1980) have undertaken a careful statistical analysis of their data in order to show that their measured Friedel-pair differences are significant and that these correspond significantly to those calculated from the structure solution of Rabinovich & Shakked (1974). Least-squares refinements on ]FI were carded out separately on the data sets (P) (that used in the structure determination of DMC by Rabinovich & Shakked, 1974) and (Pa), (Pb) and (Pc) obtained by combining (P) with the three sets of accurate measurements (a), (b) and (c) of Rabinovich & Hope (1980). Atomic parameters were taken from Rabinovich & Shakked (1974) corrected for typographic errors as indicated in the Cambridge Structural Database.…”

“…These refinements were carded out on the published data* of the compound 4,4'-dimethylchalcone (C17H16 O) -hereafter DMC -whose crystal structure was determined by Rabinovich & Shakked (1974) and refined to an R value of 0.045. The molecule of DMC is achiral and crystallizes in the space group P212121.…”