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.

Hydrogen bond studies. CXXIX. An X-ray determination of the crystal structure of hydrogen chloride hexahydrate, H9O4 +Cl−.2H2O

“…The shortest interlayer distance is 3.04 A (between two O atoms). The H9 O+ complex in HC1.6H20 has a symmetric conformation in contrast to the same complex in HBr.4H20 (Lundgren & Olovsson, 1968), where the O-H... O distances differ by up to 0-09 A and where only one of the outer water molecules has a pyramidal coordination while the other two have a tetrahedral environment. Apart from HBr.4H20 the crystal structures of HCIO4.2½H20 (Almlff, Lundgren & Olovsson, 1971)and HCIO4.3½H20 (Alml6f, 1973 can be interpreted as containing H9 O+ ions, but these complexes are not well defined.…”

“…The composition of the present compound presents the possibility of the formation of the triaquaoxonium ion, H9 O+. Hydrated oxonium ions have, in a few earlier cases, been described in terms of H904 + ions: HBr.4H20 (Lundgren & Olovsson, 1968), HCIO4.2½H20 (Alml6f, Lundgren & Olovsson, 1971), HC104.3½H20 (Alml6f,…”

Ca(H2PO4)2, a crystal structure containing unusual hydrogen bonding

“…(n+ 1)H20 has been studied by Kerbale, Searles, Zolla, Scarborough & Arshadi (1967) who showed by mass spectrometry that no unique value of n dominates. Indeed, in the crystal structure studies of (H + .nH20) X-compounds (Lundgren & Olovsson, 1968), HsOz and higher complexes were found. Thus, further investigations into the existence of dimeric, trimeric, etc., species involving H2PO~ seems warranted.…”

2,3,4,5,6,7,8,9-Octahydro-2,2,5,5,8,8-hexamethyl-1H-benzo[1,2-c:3,4-c':5,6-c'']tripyrrolium tribromide dihydrate

“…other crystalline hydrates where hydrogen bonding occurs (Lundgren, 1970;Lundgren & Olovsson, 1968;Johnson, Maier & Paul, 1973;Johnson, Frank & Paul, 1973). The top and bottom halves of this dimer approach the central 4(Br-.H20 ) network at normal van der Waals distances, indicating that forces holding the dimer together are primarily electrostatic in nature.…”