1746
J. Chem. Phys., Vol. 115, No. 4, 22 July 2001
Wang et al.
͑
5͒ The favorable reaction routes are via intermediate V. The
decomposition of the three-membered ring in V will lead
to the reaction channels ͑1͒, ͑2͒, and ͑3͒.
will lead to CO ϩCH , channel ͑3͒. As shown in Fig. 3, two
2
3
barriers, TS7 and TS9, in channel ͑3͒ are also lower. Channel
3͒ is therefore the second most significant reaction channel.
͑
The C–O band cleavage of the ring in V followed by an H
atom elimination will result in the H C O ϩH channel.
2
2
2
The reaction routes of channels ͑4͒ and ͑6͒ are relatively
simple. Because the O–O bond still remains in the final
ACKNOWLEDGMENTS
product HO of channel ͑4͒, the intermediates are not neces-
2
This work is supported by the China National Science
Foundation and by the Department of Science and Technol-
ogy of China. The authors deeply appreciate Professor Qi-He
Zhu for reviewing the manuscript.
sary to be ring-structures. The 1,4-hydrogen shifting in inter-
mediate I via TS3 accompanied by the cleavage of the C–O
bond leads to the final products C H ϩHO . Channel ͑6͒ is
2
2
2
obtained by O elimination in intermediate III via TS1. How-
ever, the high barriers ͑TS3, 41.7 kcal/mol and TS1, 38.6
kcal/mol͒ cause channels ͑4͒ and ͑6͒ to occur only in high
temperatures. Furthermore, because the total energy released
in both reactions is only 14.9 kcal/mol and 9.5 kcal/mol re-
spectively, the small amount of the exothermicity is insuffi-
cient to extensively excite the vibrations of the products. The
mechanism explains why we can only record very weak IR
emission signals for these species.
1
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9
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1
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11
are observed by the TR-FTIR spectroscope.
1
1
2
3
͑
2͒ The predominant reaction pathway is confirmed as chan-
nel ͑1͒, which has been experimentally verified and theo-
retically predicted already. The second most important
reaction route is channel ͑3͒, which has not been experi-
mentally observed.
14
15
1
1
6
7
͑
3͒ Weak IR signals may refer to C H O ( ), C H ( ),
2 2 2 1 2 2 3
1
1
8
9
HO ( ), or C H O( ). These are the products of the
2
1
2
3
1
reaction channels ͑2͒, ͑4͒, and ͑6͒.
͑
4͒ CO is the secondary reaction product. The CO source is
either the decomposition of hot HCO or the subsequent
reaction of HCOϩO →COϩHO .
2
2
0
1
H. J. Aa Jensen and P. Jørgensen, J. Chem. Phys. 80, 1204 ͑1984͒.
2
2
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