Acta Crystallographica Section B

Structural Science

Volume 57, Part 3 (June 2001)

Acta Cryst. (2001). B57, 415-427 [doi:10.1107/S010876810100430X]

Interplay between dipolar, stacking and hydrogen-bond interactions in the crystal structures of unsymmetrically substituted esters, amides and nitriles of (R,R)-O,O'-dibenzoyltartaric acid

U. Rychlewska and B. Warzajtis

Abstract: The compounds analysed are the O,O'-dibenzoyl derivatives of (R,R)-tartaric acid, asymmetrically substituted by ester, amide and nitrile groups. Benzoylation does not introduce drastic changes to the molecular conformation. All investigated molecules adopt the planar T conformation of the four-carbon chain with noticeably smaller departures from the ideal conformation than observed in the nonbenzoylated analogs. Primary and secondary amides always orient the C=O bond antiperiplanar (a) with respect to the nearest C*-O bond, while methylester groups adjust their conformation to that adopted by the amide substituent situated at the other end of the molecule. Tertiary amides and carboxyl groups place their carbonyls at the same side as the nearest C*-O bond (the s form), but often deviations from coplanarity of the two bonds are significant and higher than those observed in the nonbenzoylated series. The results presented demonstrate the importance of dipole/dipole interactions between CO and [beta] C*H groups in stabilizing the molecular conformation, and between carbonyl groups in stabilizing crystal packing of the molecules that lack classical hydrogen-bond donor groups. An illustration is provided as to how a small change in mutual orientation of molecules arranged in a close-packed fashion causes a change in the character of intermolecular interactions from van der Waals to sandwich stacking between the benzoyloxy phenyls, and to dipolar between the benzoyloxy carbonyls. Hydrogen-bonded molecules tend to orient in a head-to-tail mode; the head-to-head arrangement being limited to cases in which terminal carbonyl groups are situated at one side of the molecule. The orientation of the benzoyloxy substituents with respect to the carbon main chain is such that the (O=)C-O-C-H bond system often deviates significantly from planarity.

Online 25 May 2001


	Structure factor file (CIF format) (203.1 kbytes) Contains datablock boh1

	Structure factor file (CIF format) (139.5 kbytes) Contains datablock boh2

	Structure factor file (CIF format) (133.9 kbytes) Contains datablock boh3

	Structure factor file (CIF format) (125.0 kbytes) Contains datablock bn13

	Structure factor file (CIF format) (104.6 kbytes) Contains datablock bn23

	Structure factor file (CIF format) (105.5 kbytes) Contains datablock bom1

	Structure factor file (CIF format) (152.6 kbytes) Contains datablock nom2

	Structure factor file (CIF format) (104.7 kbytes) Contains datablock bcn3

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