Crystal structure of barbituric acid (1,4)-dioxane solvate at −173°C

Abstract

The structure of barbituric acid (1,4)-dioxane solvate has been determined by X-ray diffraction at 100 K. The compound crystallizes in the triclinic space group P $\overline 1$, with cell dimensions of a = 6.7770(16) Å, b = 9.583(2) Å, c = 9.697(2) Å, α = 85.868(5)°, β = 82.566(5)°, γ = 70.675(5)°, V = 589.0(2) ų, and Z = 1. In the solid state, one asymmetric unit consists of C₄H₄N₂O₃ ⋅ 3/2(C₄H₈O₂), each barbituric acid molecule being involved in two hydrogen bonds. The two nitrogen atoms of the acid act as hydrogen donors to two oxygen atoms, each from a different molecule of (1,4)-dioxane, which serve as the acceptors. Not all of the hydrogen-bonding capacity of the chemical moieties is used, and the principal feature of the supramolecular structure is a sawtooth ribbon composed of alternating barbituric acid and (1,4)-dioxane molecules, connected through hydrogen bonds and C$---$H ⋅⋅⋅ O interactions.