Ab Initio Kinetics for the Unimolecular Reaction C<sub>6</sub>H<sub>5</sub>OH → CO + C<sub>5</sub>H<sub>6</sub><sup>†</sup>

2006-02-02T00:00:00Z (GMT) by Z. F. Xu M. C. Lin
The unimolecular decomposition of C<sub>6</sub>H<sub>5</sub>OH on its singlet-state potential energy surface has been studied at the G2M//B3LYP/6-311G(d,p) level of theory. The result shows that the most favorable reaction channel involves the isomerization and decomposition of phenol via 2,4-cyclohexadienone and other low-lying isomers prior to the fragmentation process, producing <i>cyclo</i>-C<sub>5</sub>H<sub>6</sub> + CO as major products, supporting the earlier assumption of the important role of the 2,4-cyclohexadienone intermediate. The rate constant predicted by the microcanonical RRKM theory in the temperature range 800−2000 K at 1 Torr − 100 atm of Ar pressure for CO production agrees very well with available experimental data in the temperature range studied. The rate constants for the production of CO and the H atom by O−H dissociation at atmospheric Ar pressure can be represented by <i>k</i><sub>CO</sub> = 8.62 × 10<sup>15</sup> <i>T</i><sup>-0.61</sup> exp(−37 300/<i>T</i>) s<sup>-1</sup> and <i>k</i><sub>H</sub> = 1.01 × 10<sup>71</sup> <i>T</i><sup>-15.92</sup> exp(−62 800/<i>T</i>) s<sup>-1</sup>. The latter process is strongly <i>P</i>-dependent above 1000 K; its high- and low-pressure limits are given.