Structure of 4-(trimethylammonium)benzoate hydrate studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra

The structure of 4-(trimethylammonium)benzoate hydrate (1) has been studied by X-ray diffraction, B3LYP/6-311++G(d,p) calculations, FTIR and NMR spectroscopic techniques. The crystals are monoclinic, space group P21/c. Water molecule interacts with two 4-(trimethylammonium)benzoate molecules via two O(1w)–H⋯O hydrogen bonds of the lengths 2.781(2) and 2.774(2) Å. The FTIR spectrum of the solid compound is consistent with the X-ray results. The second-derivative IR spectrum of 1 and calculated frequencies for the optimized structure 2 are used to explain frequencies in the experimental FTIR spectrum. The interpretation of 1H and 13C NMR spectra have been based on 2D experiments and calculated GIAO/B3LYP/6-311++G(d,p) magnetic isotropic shielding constants. Interesting are dimer structures (6 and 7) estimated by B3LYP/6-311++G(d,p) calculations, which are stabilized by N+⋯O–C electrostatic interactions.