1398 J. Phys. Chem. A, Vol. 109, No. 7, 2005
Mullen and Smith
with the data presented in Figure 8, where at low temperature
the reaction is likely proceeding via a complex addition
intermediate that can either be stabilized by collisions, or react
in an elimination or fragmentation process. Under these
circumstances, the data of Rohrig et al. is best understood as
participation of NH in either addition/elimination or abstraction
chemistry over a portion of the potential energy surface with a
barrier. Moreover, the reactions of hydroxyl radical with propene
whether the adduct proceeds to products or is stabilized by
additional collisions. Further, experiments focusing on the
pressure dependence and kinetic isotope effects would help to
resolve this issue, as would an accurate potential energy surface.
An understanding of the chemistry of these systems will help
to determine their importance to the atmospheric chemistry of
Saturn’s moon Titan, as well as other low-temperature environ-
ments where these molecules might be found.
-
10
3
(
(
1
k103K ) (0.81 ( 0.18) × 10
cm /s) and 1-butene (k103K )
cm /s) and with butenes (k75K ≈ 3 ×
-
10
3
54
1.24 ( 0.27) × 10
Acknowledgment. The authors gratefully acknowledge
financial support of this work by the National Science Founda-
tion through Grant No. CHE-9984613. In addition C.M. would
like to thank Dr. Andrey E. Belikov for his insight and scientific
advice throughout the course of the experiments.
-
10
3
55
0
cm /s) have been studied at low temperature in Laval
nozzle expansions and their rates are found to be fast and display
negative temperature dependence. Sims et al. find strong
evidence for the absence of any maximum of electronic potential
energy along the minimum energy path leading from separated
55
reagents to the radical adduct for the OH + butanes reactions,
while Vakhtin et al. expect the reactions of OH + propene and
-butene to be in their high-pressure limit under the low
References and Notes
1
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5
4,56
temperature and pressure conditions of their experiment.
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6
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(
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6, 175.
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(
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(
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3
+
hydrocarbon systems. They find good correlation between
(
the barriers for the NH and O isoelectronic species with
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(
3
participating in electrophilic addition. While both O( P) and
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3
-
NH( Σ ) are isoelectronic, and both form a diradical upon
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(
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(
1
(
3
formation of an adduct on an attractive potential, while the O( P)
(
experiences some electronic repulsion upon approach to the π
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3
O( P) + unsaturated hydrocarbon systems barriers are com-
mon.58
(
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1
5. Conclusion
(
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3
-
The reactions of NH(X Σ ) with NO and the hydrocarbons
methane, ethane, ethylene, acetylene, propene, and diacetylene
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(
(
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(
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(
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