The crystal structure of an orthorhombic form of L-cysteine has been determined by X-ray diffraction. The molecule crystallizes in the space group P2~2121 with four molecules in a unit cell of dimensions a = 8" 116 + 3, b = 12.185 + 4, c = 5.426 + 2 A; density Dx = 1.50, D .... = 1.47 g cm-3. After full-matrix refinement, the R value was 3.75 % for the 1062 observed reflexions. The molecule exists as a zwitterion with a three-dimensional network of hydrogen bonds. Conformational angles are close to those observed in other cysteinyl residues. The thiol hydrogen was not located.
The crystal structure of 1.1 '-binaphthyl has been determined by X-ray analysis. The crystals are monoclinic space group C2/c, with a = 20.98. b = 6.35, c = 10.1 3 8, = 105.1 7': Z = 4. The molecule exists in a cisconfiguration with an angle of 68" between the planes of the two naphthalene residues, the dimensions of which are not significantly different from those of naphthalene itself. The sp2-sp2 single-bond between the two ring systems has a length of 1.475 f 0.005 8. The final R is 0.085 for 131 5 observed reflections.
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