Hydrogen-Bond Studies. XXX. The Crystal Structure of Hydrogen Bromide Tetrahydrate, (H7O3)+(H9O4)+2Br−·H2O

Abstract

The crystal structure of hydrogen bromide tetrahydrate (HBr·4H2O) has been determined from three-dimensional single-crystal x-ray data recorded at −180°C. Crystals of this compound are monoclinic, space group P21, with four formula units in a cell with the dimensions: a = 7.043, b = 11.466, c = 7.339 Å, β = 110.85°. The structure determination shows that the compound may be formulated as (H7O3)+(H9O4)+2Br−·H2O. The hydrogen-bond lengths within H7O3+ are 2.465 and 2.498 Å, and within H9O4+2.496, 2.587, and 2.588 Å. Other O–H···O bonds in the structure are about 2.75 Å.