Hydrogen bonding induced proton exchange reactions in dense D{sub 2}-NH{sub 3} and D{sub 2}-CH{sub 4} mixtures
- Institute for Shock Physics, Department of Physics and Department of Chemistry, Washington State University, Pullman, Washington 99164 (United States)
We have investigated high-pressure behaviors of simple binary mixtures of NH{sub 3} and D{sub 2} to 50 GPa and CH{sub 4} and D{sub 2} to 30 GPa using confocal micro-Raman spectroscopy. The spectral data indicate strong proton exchange reactions occur in dense D{sub 2}-NH{sub 3} mixture, producing different isotopes of ammonia such as NH{sub 3}, NH{sub 2}D, NHD{sub 2}, and ND{sub 3}. In contrast, the proton exchange process in dense D{sub 2}-CH{sub 4} mixture is highly limited, and no vibration feature is apparent for deuterated methane. The vibrational modes of H{sub 2} isotopes in D{sub 2}-NH{sub 3} are blue shifted from those of pure H{sub 2} isotopes, whereas the modes of D{sub 2}-CH{sub 4} show overall agreement with those in pure D{sub 2} and CH{sub 4}. In turn, this result advocates the presence of strong repulsion and thereby internal pressure in D{sub 2}-NH{sub 3} mixture, which are absent in D{sub 2}-CH{sub 4}. In fact, the bond length of hydrogen molecules in D{sub 2}-NH{sub 3}, calculated from the present spectral data, is shorter than that observed in pure hydrogen – supporting the enhanced intermolecular interaction in the mixture. Comparing the present spectral results with those previously observed in D{sub 2}-H{sub 2}O mixtures further suggests that the strength of repulsive interaction or the magnitude of internal pressure in the mixtures is proportional to the strength of hydrogen bonding in H{sub 2}O, NH{sub 3}, and CH{sub 4} in decreasing order. Hence, we suggest that the proton exchange is assisted by hydrogen bonding in these molecules.
- OSTI ID:
- 22255208
- Journal Information:
- Journal of Chemical Physics, Vol. 140, Issue 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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