7606 J. Phys. Chem. A, Vol. 105, No. 32, 2001
Aschmann et al.
TABLE 5: Product Formation Yields from Reactions of the
Acknowledgment. The authors thank the California Air
Resources Board for supporting this research through Contract
No. 97-312. The statements and conclusions are those of the
authors and not necessarily those of the California Air Resources
Board.
OH Radical with a Series of C -C10 Alkanes Studied in This
5
Laboratory, in the Presence of NO (This Work and
Reference 15)
yield (%)
alkyl
hydroxy- hydroxy-
alkane
n-pentane
n-hexane
n-heptane
n-octane
n-decane
carbonylsa nitrates carbonyls
nitrates
References and Notes
47
10
e1
e1
10.5
14.1
17.8
22.6
22.6
18
36
53
46
27
22
11
37
2.6
4.6
4.7
5.4
2.4
1.7
2.3
(1) Atkinson, R. Atmos. EnViron. 2000, 34, 2063.
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(
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3
,4-diethylhexane
∼40
n-butylcyclohexane
7
19
(
a
of the alkoxy radicals.3,11
From decomposition or reaction with O
2
Pitts, J. N., Jr. J. Phys. Chem. 1982, 86, 4563.
The cited yields account for the formation of two carbonyls as
coproducts in many instances and hence the cited yields refer to the
reaction pathways.
(7) Atkinson, R.; Carter, W. P. L.; Winer, A. M. J. Phys. Chem. 1983,
8
7, 2012.
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1987, 5, 91.
(
(
carbonylnitrates of molecular weight 233, hydroxydicarbonyls
of molecular weight 186, and, to a lesser extent, dicarbonyls of
molecular weight 170. As mentioned above, ion peaks attributed
to products of molecular weight 170, 217 and, possibly, 233
were observed in the API-MS analyses. In the case of the
hydroxydicarbonyls of molecular weight 186, it is possible that
the major ion peak observed from this product in the positive
(
(
10) Harris, S. J.; Kerr, J. A. Int. J. Chem. Kinet. 1989, 21, 207.
11) Atkinson, R.; Kwok, E. S. C.; Arey, J.; Aschmann, S. M. Faraday
Discuss. 1995, 100, 23.
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Chem. A 1997, 101, 8042.
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Chem. A 1999, 103, 2688.
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104, 5072.
+
ion mode was the [M+H-H2O] at 169 u, which is isobaric
with the [M+H-H2] of the molecular weight 170 hydroxy-
(15) Arey, J.; Aschmann, S. M.; Kwok, E. S. C.; Atkinson, R. J. Phys.
+
Chem. A 2001, 105, 1020.
carbonyl(s), and that the observed 185 u ion peak (Figure 5B)
is the [M+H-H2] of this hydroxydicarbonyl.
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Pollut. Control Assoc. 1981, 31, 1090.
+
Our product yield data given in Table 4 (assuming that butanal
and cyclohexanone are formed as coproducts) account for 65%
of the reaction products and pathways (and taking the uncertain-
ties into account), with a range of ∼40-110%.
(
19) Atkinson, R.; Tuazon, E. C.; Aschmann, S. M. EnViron. Sci.
Technol. 1995, 29, 1674.
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(
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Atmospheric Implications. Combining our room-tempera-
ture rate constants for the reactions of OH radicals with
n-decane, 3,4-diethylhexane and n-butylcyclohexane with a 24-
2
(
6
hr average OH radical concentration of 1.0 × 10 molecule
P. B. J. Phys. Chem. A 1998, 102, 8903.
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Pitts, J. N., Jr. Int. J. Chem. Kinet. 1982, 14, 781.
-3
36,37
cm (the global tropospheric average)
leads to tropospheric
lifetimes of 0.9 days, 1.6 days and 0.7 days for n-decane, 3,4-
diethylhexane, and n-butylcyclohexane, respectively. The prod-
ucts observed and quantified show that the detailed reactions
after the initial H-atom abstraction depend on the structure of
the alkane, with the alkoxy radicals produced from n-decane
and n-butylcyclohexane undergoing largely isomerization and
leading to hydroxycarbonyl formation, whereas the alkoxy
radicals formed from 3,4-diethylhexane also decompose to a
significant or dominant extent, thereby leading to volatile
products which can be readily analyzed by gas chromatography.
As shown in Table 5 for a series of C5-C10 alkanes for which
hydroxycarbonyl and hydroxynitrate yields are available (this
work and ref 15), the major reaction products of several alkanes
are now known and a significant fraction of the atmospheric
reaction products of gC5 n-alkanes (and other alkanes whose
intermediate alkoxy radicals can isomerize) are comprised of
hydroxycarbonyls and hydroxynitrates. The estimation method
(
25) Nolting, F.; Behnke, W.; Zetzsch, C. J. Atmos. Chem. 1988, 6, 47.
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Atmos. EnViron. 1988, 22, 1113.
(
27) Kwok, E. S. C.; Atkinson, R. Atmos. EnViron. 1995, 29, 1685.
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Estimation Methods for Chemicals: EnVironmental and Health Sciences;
Boethling, R. S., Mackay, D., Eds.; Lewis Publishers: Boca Raton, 2000,
pp 335-354.
(
(
29) Atkinson, R. J. Phys. Chem. Ref. Data 1994, Monograph 2, 1.
30) Dagaut, P.; Wallington, T. J.; Liu, R.; Kurylo, M. J. J. Phys. Chem.
1988, 92, 4375.
(
31) Aschmann, S. M.; Atkinson, R. Int. J. Chem. Kinet. 1999, 31, 501.
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T. J.; Vereecken, L.; Peeters, J. J. Phys. Chem. A 1998, 102, 8116.
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Kinetics and Thermodynamics Division, National Institute of Standards and
Technology, Gaithersburg, MD, January 1994.
(
34) Kerr, J. A.; Stocker, D. W. Strengths of Chemical Bonds in
Handbook of Chemistry and Physics, 80th ed.; Lide, D. R., Ed.; CRC
Press: Boca Raton, FL, 1999-2000.
(35) Atkinson, R.; Baulch, D. L.; Cox, R. A.; Hampson, R. F., Jr.; Kerr,
J. A.; Rossi, M. J.; Troe, J. J. Phys. Chem. Ref. Data 2000, 29, 167.
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Cunnold, D. M.; Fraser, P. J.; Hartley, D. E.; Simmonds, P. G. Science
2,3
proposed by Atkinson and revised by Aschmann and Atkin-
3
1
son appears to be useful in that its quantitative predictions
concerning the products formed and their yields are in generally
good agreement with our experimental observations.
1
995, 269, 187.
37) Hein, R.; Crutzen, P. J.; Heimann, M. Global Biogeochem. Cycles
1997, 11, 43.
(