Proton affinity and absolute heat of formation of trifluoromethanol
- Purdue Univ., West Lafayette, IN (United States)
The proton affinity and absolute heat of formation of trifluoromethanol have been derived from translational energy threshold measurements for reactions involving oxygen-protonated trifluoromethanol. The reaction of ionized iodotrifluoromethane with water was used to prepare CF{sub 3}OH{sub 2}{sup +} in the flow tube of a flowing afterglow triple-quadrupole instrument. The isomeric cluster ion, (HF)CF{sub 2}OH{sup +}, was shown to be more stable than CF{sub 3}OH{sub 2}{sup +} by the base-catalyzed conversion of CF{sub 3} OH{sub 2}{sup +} to (HF)CF{sub 2}OH{sup +} using either SO{sub 2} or OCS as the catalyst. The proton affinity of CF{sub 3}OH at oxygen was determined from the enthalpy change for the endothermic proton transfer reaction CF{sub 3}OH{sub 2}{sup +} + CO {yields} CF{sub 3}OH + HCO{sup +}. The measured enthalpy change was combined with the known value for the proton affinity of CO (141.9 kcal mol{sup -1}) to yield a value for the oxygen proton affinity of CF{sub 3}OH. The dissociation energy for the loss of water from CF{sub 3}OH{sub 2}{sup +} was measured by energy-resolved collision-induced dissociation. This value was used in a thermochemical cycle along with the measured proton affinity of CF{sub 3}OH to derive the gas-phase heat of formation of CF{sub 3}OH. This experimental value is slightly lower than, but in good agreement with, the 298 K heat of formation of CF{sub 3}OH that is predicted by high-level molecular orbital calculations. 37 refs., 7 figs., 3 tabs.
- OSTI ID:
- 420868
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 40 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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