Hydrogen bonding Part 34. Thermodynamics of dissociation, stoichiometry, and IR study of the hydrates of N,N-diphenylpiperazine dioxide and N,N-di-p-tolylpiperazine dioxide

Abstract Vapor pressure versus H 2 O content studies show that N , N -diphenylpiperazine dioxide does not form any hydrates other than the previously reported dihydrate and octahydrate. N , N -Di- p -tolylpiperazine dioxide forms a previously unreported dihydrate in addition to the known, tetrahydrate. Thermodynamic values for the dissociations of these four hydrates were determined through equilibrium dissociation vapor pressure measurements. The HOH⋯ON hydrogen bonds in the two dihydrates appear to be significantly weaker than those in the higher hydrates; this conclusion is supported by IR spectral observations. IR comparisons with other hydrates of known structure suggest that H 2 0 molecules in the two N , N -diarylpiperazine dioxide dihydrates bridge between two amine oxide oxygens.