G. Pawley, E. A. Yeats
Oct 15, 1969
Citations
0
Influential Citations
50
Citations
Journal
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry
Abstract
sec-butyl and 5-ethyl-5-(1-methylbutyl) barbituric acids. Crystals of these compounds have been shown to have structures which closely resemble amobarbital II (Craven & Cusatis, unpublished). However, it is unlikely that barbiturates substituted with unbranched chains at C(5) could have a double ribbon structure because the chain packing would be very inefficient. A double ribbon structure is not found in barbital I, II or IV* (Craven, Vizzini & Rodrigues, 1969). More work is needed to determine the extent to which chain length in a C(5) substituent affects the occurrence of double ribbons in barbiturate crystal structures. It is probable that length is a less critical factor than cross sectional area. Solid solutions and molecular complex formation have been reported in many binary systems of 5,5'dialkylbarbiturates (Brandst/itter-Kuhnert & Vlachopoulos, 1967). This suggests the existence of hydrogen bonded frameworks in the solid state which are not greatly perturbed when one barbiturate is substituted for another. The double ribbon structure is well suited to this role, and in fact occurs in solid solutions in at least one such binary system (amobarbital/vinbarbital; Craven & Cusatis, unpublished).