The crystal structure of α- glycylglycine

The cystal structure of the &#945; crystal form of glycylglyeine, -CO<SUB>2</SUB>CH<SUB>2</SUB>NHCOCH<SUB>2</SUB>NH<SUB>3</SUB><SUP>+</SUP>, has been investigted. The cell dimensions are a = 7&#183;70, b = 9&#183;57, c = 9&#183;48 &#197; &#946; = 124&#176;35'. The space group is P2<SUB>1</SUB>/a with four molecules per cell. Mo k&#945; rays were used. The trial structure was derived by use of part-cell Patterson methods and modlfied Banerjee equations. Final refinement was by block-diagnol anisotropic least-squares adjustment to an R of 12&#183;3 and yielded standard deviations of about 0&#183;007&#197; in bond lengths.The intramolecular chemical bond lengths and interbond angles agree well with those found for the same molecule in the previously reported &#946; crystal form but the configuration of the molecule is somewhat different. There is an angle of about 22&#183;4&#176; between the plane of the amide group and that of the carboxyl group. In the &#946; crystal these group were coplanar within experimental error. Since the &#945; form is probably the stable form, this distortion presumbly permits better molecular packing with stronger hydrogen bonds and van Waals interactions