Hydrogen bonding Part 44. 1-Methyl-1,3,5,7-tetra-aza-adamantan-1-ium (N-methylhexamethylenetetramine cation) halide hydrates: IR and thermodynamic study of planar C2h(H2O*Br-)2 and (H2O*Cl-)2 clusters, a possible C2h(H2O*I-)2 cluster,and two higher Cl- hydrates

Article abstract of DOI:10.1016/0022-2860(92)85018-C

The IR spectrum of the C_2h(H2O*Br^-)2 cluster in the bromide monohydrate of the N-methylhexamethylenetetramine cation (MHMTA⁺) correlates well with that of the C_2h(H2O*Cl^-)2 cluster in the tetraethylammonium chloride monohydrate.MHMTA⁺Cl^- forms a monohydrate which contains a similar cluster, as well as a dihydrate and trihydrate.Equilibrium dissociation vapor pressure measurements show that the minimum value for H-O-H...X^- hydrogen bonds is about 6.5 kcal mol^-1 in the bromide monohydrate and about 7.5 kcal mol^-1 in the chloride monohydrate.MHMTA⁺I^- forms an ephemeral monohydrate; dissociation measurements over a limited range suggest a minimum value of about 8 kcal mol^-1 for H-O-H...I^- hydrogen bonds.The IR spectrum of the iodide monohydrate does not distinguish clearly between a planar cyclic and an extended spiral structure for the water-iodide structure.