TY - JOUR
T1 - Temperature dependence of the rate constants for the reactions of C 2 H with C 2 H 2 , H 2 , and D 2
AU - Koshi, Mitsuo
AU - Fukuda, Koichi
AU - Kamiya, Kenshu
AU - Matsui, Hiroyuki
PY - 1992/11/1
Y1 - 1992/11/1
N2 -
Reactions of the ethynyl (C
2
H) radical with C
2
H
2
, H
2
, and D
2
were studied over the temperature range 298-438 K by time-resolved mass spectrometry. The rate of the reaction with C
2
H
2
was followed by measuring the appearance rate of C
4
H
2
. The rates of the reactions with H
2
and D
2
were deduced by measuring the dependence of C
4
H
2
production (arising from the reaction of C
2
H with the C
2
H
2
precursor) on the partial pressure of added H
2
or D
2
. The rate constants for the reaction C
2
H + C
2
H
2
→ C
4
H
2
+ H were also measured following reflected shock waves by monitoring H atom resonant absorption at 121.6 nm. In both experiments, the C
2
H radical was generated by ArF (193-nm) laser photolysis of C
2
H
2
. A rate constant of (1.5 ± 0.3) × 10
-10
cm
3
molecule
-1
s
-1
was obtained for reaction 1 without any temperature dependence at T = 298-2177 K. The results for the reactions C
2
H + H
2
→ C
2
H
2
+ H and C
2
H + D
2
→ C
2
HD + D could be represented by the Arrhenius expressions, k
2
= (1.8 ± 1.0) × 10
-11
exp(-(1090 ± 299)/T) and k
3
= (1.4 ± 0.8) × 10
-11
exp(-(1377 ± 301)/T) cm
3
molecule
-1
s
-1
, over the range of T = 298-438 K. The classical barrier height for reactions 2 and 3 was estimated to be 2 kcal/mol on the basis of conventional transition-state theory. The isotope effects on reactions 2 and 3 calculated with Wigner tunneling correction were in good agreement with the present results.
AB -
Reactions of the ethynyl (C
2
H) radical with C
2
H
2
, H
2
, and D
2
were studied over the temperature range 298-438 K by time-resolved mass spectrometry. The rate of the reaction with C
2
H
2
was followed by measuring the appearance rate of C
4
H
2
. The rates of the reactions with H
2
and D
2
were deduced by measuring the dependence of C
4
H
2
production (arising from the reaction of C
2
H with the C
2
H
2
precursor) on the partial pressure of added H
2
or D
2
. The rate constants for the reaction C
2
H + C
2
H
2
→ C
4
H
2
+ H were also measured following reflected shock waves by monitoring H atom resonant absorption at 121.6 nm. In both experiments, the C
2
H radical was generated by ArF (193-nm) laser photolysis of C
2
H
2
. A rate constant of (1.5 ± 0.3) × 10
-10
cm
3
molecule
-1
s
-1
was obtained for reaction 1 without any temperature dependence at T = 298-2177 K. The results for the reactions C
2
H + H
2
→ C
2
H
2
+ H and C
2
H + D
2
→ C
2
HD + D could be represented by the Arrhenius expressions, k
2
= (1.8 ± 1.0) × 10
-11
exp(-(1090 ± 299)/T) and k
3
= (1.4 ± 0.8) × 10
-11
exp(-(1377 ± 301)/T) cm
3
molecule
-1
s
-1
, over the range of T = 298-438 K. The classical barrier height for reactions 2 and 3 was estimated to be 2 kcal/mol on the basis of conventional transition-state theory. The isotope effects on reactions 2 and 3 calculated with Wigner tunneling correction were in good agreement with the present results.
UR - http://www.scopus.com/inward/record.url?scp=33751390954&partnerID=8YFLogxK
U2 - doi.org/10.1021/j100203a048
DO - doi.org/10.1021/j100203a048
M3 - Article
AN - SCOPUS:33751390954
VL - 96
SP - 9839
EP - 9843
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
SN - 0022-3654
IS - 24
ER -