Butallyl-onal 1,4-dioxane hemisolvate.

THE ASYMMETRIC UNIT OF THE TITLE COMPOUND [SYSTEMATIC NAME: 5-(1-bromo-prop-2-en-1-yl)-5-sec-butyl-pyrimidine-2,4,6-trione 1,4-dioxane hemisolvate], C(11)H(15)BrN(2)O(3)·0.5C(4)H(8)O(2), contains one half-mol-ecule of 1,4-dioxane and one mol-ecule of butallyl-onal, with an almost planar barbiturate ring [largest deviation from the mean plane = 0.049 (5) Å]. The centrosymmetric dioxane mol-ecule adopts a nearly ideal chair conformation. The barbiturate mol-ecules are linked together by an N-H⋯O hydrogen bond, giving a single-stranded chain. Additionally, each dioxane mol-ecule acts as a bridge between two anti-parallel strands of hydrogen-bonded barbiturate mol-ecules via two hydrogen bonds, N-H⋯O(dioxane)O⋯H-N. Thus, a ladder structure is obtained, with the connected barbiturate mol-ecules forming the 'stiles' and the bridging dioxane mol-ecules the 'rungs'.