Hydrogen bonding in the gas phase. Part 2.—Determination of thermodynamic parameters for amine–methanol systems from pressure, volume, temperature measurements

Abstract

Pressure, volume, temperature studies have been made of gas phase amine-methanol systems. An apparatus which allows such observations without the need for weighing of original samples to be mixed is described. Equilibrium constants for the formation of hydrogen bonded complexes over the temperature range 2545°C are reported and thermodynamic parameters have been evaluated for systems formed by methanol with methylamine, dimethylamine, trimethylamhe and triethylamine. The values obtained are discussed in comparison with solution values. Larger values of AH" are found for gas phase complexes than for the corresponding complexes in solution, and the effect is interpreted in terms of solvation. It is found that the electron donating powers of the amines, as measured by AH" values for hydrogen bond formation in the gas phase, increase with increasing methylation of the amine. Wavenumber displacement AV of the 0-H stretching frequency on formation of such hydrogen bonds, are found to correlate with AHo values, and it is suggested that AV values may be used to estimate AH' values.

B3LYP and MP2 Calculations of the Enthalpies of Hydrogen-Bonded Complexes of Methanol with Neutral Bases and Anions: Comparison with Experimental Data

“…32 Because they were obtained in the same work by the same method, the results of this systematic study 32 of the methanol-amine complexes are expected to be self-consistent. Moreover, the methanol-trimethylamine value is supported by an infrared result.…”

Similar Strength of the NH···O and NH···S Hydrogen Bonds in Binary Complexes

“…The enthalpy of complex formation for the MeOH−DMA complex was predicted to be −28.3 kJ mol −1 with the wB97XD/aVTZ method, in reasonable agreement with experimental results of −25.9 ± 1.0 and −35.8 ± 3.9 kJ mol −1 in two separate experiments, taking into account that the enthalpy is difficult to both calculate and determine experimentally. 40,41 In comparison, the corresponding value predicted with the B3LYP/aVTZ method is −19.8 kJ mol −1 . 40 The structures of the compounds were also optimized at the CCSD(T)-F12a 42 /VDZ-F12 43 (F12) level of theory using Molpro.…”

Fundamental and overtone vibrational spectroscopy, enthalpy of hydrogen bond formation and equilibrium constant determination of the methanol–dimethylamine complex

“…[16][17][18][19][20][21] Thus, methanol-amine complexes have been studied frequently. 19,[22][23][24][25][26][27][28][29][30] Vibrational spectroscopy is one of the most useful experimental tools in the study of hydrogen bonded clusters. [31][32][33][34][35][36][37][38][39] Molecular complexes can be identified by new ro-vibronic bands that are not present in the spectra of the monomers.…”