G. Reeke, R. E. Marsh
Jun 10, 1966
Citations
0
Influential Citations
17
Citations
Journal
Acta Crystallographica
Abstract
The crystal structure of 5-ethyl-6-methyluracil has been determined and refined by three:dimensional least-squares methods. The final R index for 1369 observable reflections is 0.080, and the standard deviations in the positions of the C, N, and O atoms are in the range 0.002-0.005 ~. The crystals are triclinic, space group P i, with a = 7.478, b = 11.803, e = 4.776/~, e = 99-39, fl= 107.65, 7= 92.14°; there are two molecules per unit cell. The bond distances and angles are very close to those in thymine monohydrate. The pyrimidine ring is significantly non-planar, being buckled about the C(2)-C(5) line apparently to relieve strain between the substituent groups. Two pairs of N H . . " O hydrogen bonds, 2.78 and 2.82/~ in length and arranged about centers of symmetry, hold the molecules together to form chains along the [102] direction.