title: Structure and hydrogen bonding in 2,4-dihydroxybenzoic acid at 90, 100, 110 and 150 K; a theoretical and single-crystal X-ray diffraction study.
abstract: A new polymorph of 2,4-dihydroxybenzoic acid is reported. The structure was characterized by multiple-temperature X-ray diffraction and solid-state DFT computations. The material shows a geometric pattern of hydrogen bonding consistent with cooperativity between the intermolecular carboxylic acid dimer and intramolecular hydrogen bonds. The presence of proton disorder within this hydrogen-bond system, which would support such a cooperative model, was not fully ruled out by the initial X-ray studies. However, solid-state calculations on the three possible end-point tautomers indicate that the dominant crystallographically observed configuration is substantially lower in energy than the other tautomers (by at least 9 kJ mol(-1)), indicating that no disorder should be expected. It is therefore concluded that no disorder is observed either in the intra- or intermolecular hydrogen bonds of the title compound and that the cooperativity between the hydrogen bonds is not present within the temperature range studied.
authors: Department of Chemistry and WestCHEM Research School, University of Glasgow, Glasgow G12 8QQ, Scotland.
authors: Andrew
authors: A
authors: Parkin
authors: Martin
authors: M
authors: Adam
authors: Richard I
authors: RI
authors: Cooper
authors: Derek S
authors: DS
authors: Middlemiss
authors: Chick C
authors: CC
authors: Wilson