Kinetics study of the gas-phase reactions of C2F 5OC(O)H and n-C3F7OC(O)H with OH radicals at 253-328 K

Article abstract of DOI:10.1016/j.cplett.2004.11.019

The rate constants, k₁ and k₂ for the reactions of C₂F₅OC(O)H and n-C₃F₇OC(O)H with OH radicals were measured using an FT-IR technique at 253-328 K. k₁ and k₂ were det

Full text of DOI:10.1016/j.cplett.2004.11.019

Chemical Physics Letters 400 (2004) 563–568
www.elsevier.com/locate/cplett
Kinetics study of the gas-phase reactions of C F OC(O)H and
2
5
n-C F OC(O)H with OH radicals at 253–328 K
3
7
*
L. Chen , S. Kutsuna, K. Tokuhashi, A. Sekiya
National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan
Received 16 September 2004; in final form 1 November 2004
Available online 21 November 2004
Abstract
The rate constants, k
1
2 2 5 3 7
and k for the reactions of C F OC(O)H and n-C F OC(O)H with OH radicals were measured using an
ꢀ
13
ꢀ12
FT-IR technique at 253–328 K. k and k were determined as (9.24 ± 1.33) · 10
exp[ꢀ(1230 ± 40)/T] and (1.41 ± 0.26) · 10
. The random errors reported are ±2 r, and potential systematic errors of 10% could add
OC(O)H and n-C OC(O)H with respect to reaction with OH radicals were
1
2
3
ꢀ1 ꢀ1
exp[ꢀ(1260 ± 50)/T] cm molecule
s
to the k
1
and k
2
. The atmospheric lifetimes of C
2
F
5
3 7
F
estimated at 3.6 and 2.6 years, respectively.
2004 Elsevier B.V. All rights reserved.
ꢀ
1
. Introduction
Two hydrofluoroethers (HFEs), C F OCH and
n-C F OCH , have been developed to replace hydro-
C
2
F
5
OCðOÞH þ OH ! products
k
1
ð1Þ
ð2Þ
n-C F OCðOÞH þ OH ! products k2
3
7
2
5
3
3
7
3
Therefore, the rate constants for OH radical reaction,
k and k , are important factors in the atmospheric
chlorofluorocarbons and hydrofluorocarbons [1,2].
These HFEs have stratospheric–ozone depletion poten-
tials of zero because they do not contain Cl atoms. How-
ever, they have been reported to have relative short
atmospheric lifetimes of 4.9 and 5.0 years, respectively,
which were estimated from the rate constants of their
OH radical reactions at 272 K by scaling from the life-
1
2
chemistry of these compounds. An upper limit of
ꢀ
15
3
cm molecule
ꢀ1 ꢀ1
8.2 · 10
s for k has been estimated
2
on the basis of the rate constant k(n-C F O
3
7
ꢀ
15
3
C(O)H + Cl), which is (8.2 ± 2.2) · 10
cule
cm mole-
ꢀ1
at 295 K [4]. However, k and k have not
ꢀ
1
s
1
2
been measured. In this study, we determined k and k
1
2
time of CH CCl (6 years) [3]. Two perfluoroalkyl for-
3
3
by using a Fourier transform infrared spectroscopic
3
technique in an 11.5-dm reaction chamber at 253–328
mates, C F OC(O)H and n-C F OC(O)H, are major
2
5
3
7
primary products of the oxidation of C F OCH and
3
2
5
K. The atmospheric lifetimes of C F OC(O)H and
2
5
n-C F OCH by OH radicals in the atmosphere [4,5].
3
7
3
n-C F OC(O)H with respect to reaction with OH radi-
3 7
These perfluoroalkyl formates are potential greenhouse
gases owing to their strong absorption at 1000–1300
cm , and thus an assessment of their atmospheric
chemistry is needed [4,5]. In the atmosphere, they can
be removed by reaction with OH radicals:
cals were estimated from the data for k and k at 272 K.
1
2
ꢀ
1
2. Experimental
The C F OCH and n-C F OCH samples (99%
2
5
3
3
7
3
pure) used in this study were provided by the Research
Institute of Innovative Technology for the
Earth (RITE). Measurements were carried out in an
*
Corresponding author. Fax: +81 298 61 8163.
E-mail address: l-chen@aist.go.jp (L. Chen).
0
009-2614/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.cplett.2004.11.019

564
L. Chen et al. / Chemical Physics Letters 400 (2004) 563–568
3
1.5-dm cylindrical quartz chamber (diameter, 10 cm;
ꢀ5 ꢀ1
s (one lamp), respec-
1
lamps) and (1.24 ± 0.13) · 10
tively); [OH] is the average concentration of OH
length, 146 cm) with an external jacket [6]. The temper-
ature in the reaction chamber was controlled by circulat-
ing heated water or a coolant through the external
jacket. One or Two 40-W low-pressure Hg lamps
av
radicals in the reaction chamber; D[n-C F
OCH ] ,
3 t
n
2n+1
[n-C F
n
OC(O)H] and [n-C F
n
OCH ] are, respec-
2n+1 3 0
2n+1
t
tively, the concentration of n-C F
n
OCH consumed,
3
2n+1
(
as the UV light source.
254 ± 8 nm) (GL-40, National Co., Japan) were used
the concentration of n-C F2n+1OC(O)H formed at
n
reaction time t, and the initial concentration of
n-C F
The OH radicals were generated by UV photolysis of
O in the presence of water vapor at an initial pressure
of 200 Torr of He, as illustrated in Eqs. (3) and (4):
OCH . However, Eq. (I) is based on the pre-
2n+1 3
n
supposition that the concentration of OH radicals is
approximately constant during measurement [7]. In this
study, a nearly constant OH radical concentration were
produced by means of continuous addition of the
3
1
O
3
þ hm ! Oð DÞ þ O
2
ð3Þ
ð4Þ
1
O
3
/O
The typical initial concentrations (in molecules cm
gas mixture into the chamber during irradiation.
2
Oð DÞ þ H O ! 2OH
2
ꢀ
3
)
1
5
He was used as a diluent because of its low quenching
1
efficiency for O( D). The O /O (3%) gas mixture was
were 1.0 · 10
(C F OCH or n-C F OCH ) and
2 5 3 3 7 3
1
7
3
2
5.6 · 10 (H O) in He at 200 Torr. The decay of reactant
2
generated from pure O with a silent-discharge ozone
2
was ꢃ90% over a 60-min irradiation period at 298 K.
generator (ECEA-1000, EBARAJITSUGYO, Japan).
The O /O gas mixture was continuously introduced
The loss of n-C F
n
OCH and the formation of
3
2n+1
3
2
n-C F2n+1OC(O)H3 were monitored with an FT-IR
n
3
ꢀ1
into the chamber at a flow rate of 6–20 cm min
during the UV irradiation period [6].
spectrometer (JIR-6500, JEOL Ltd., Japan) with a
nickel-coated aluminum multiple-reflection IR cell
3
375 cm ; optical path length, 3 m) at a resolution of
In the measurement of the rate constants,
n-C F OCH (n = 2 and 3) served as both a reference
compound and a precursor for n-C F2n+1OC(O)H.
(
ꢀ1
n
2n+1
3
0.5 cm . The sample in the reaction chamber was con-
tinuously circulated through the IR cell by a magneti-
cally driven glass circulating pump at a flow rate of 850
n
n-C F2n+1OC(O)H not only reacts with OH radicals
n
3
ꢀ1
but also undergoes photolysis under UV irradiation.
Therefore, n-C F2n+1OC(O)H is the intermediate in the
consecutive reactions illustrated in Eqs. (5)–(7)
cm min
during UV irradiation. The absorption
2
ꢀ1
ꢀ1
n
cross-sections (e) (cm molecule
(base 10)) of
ꢀ20
C F OCH (8.08 · 10
9.73 · 10
at 1461 cm ), n-C F OCH
at 1461 cm ), CF C(O)F (1.72 · 10
2
5
3
3
7
3
ꢀ19
ꢀ
20
ꢀ1
(
3
n-C
n
F
2nþ1OCH
3
þ OH ! an-C
n
F
2nþ1OCðOÞH
ꢀ
1
ꢀ19
ꢀ1
at 1883 cm ), C F C(O)F (2.96 · 10
at 1883
2
5
þ other products
ð5Þ
ð6Þ
ð7Þ
ꢀ1
ꢀ19
cm ), and COF (6.3 · 10
at 1928 cm ) were cal-
2
culated from the IR spectra of their He mixtures of
known concentration. The following reagents were
used: CF C(O)F (99%, RITE); C F C(O)F (97%,
n-C
n-C
n
n
F
F
2nþ1OCðOÞH þ OH ! products
3
2 5
2nþ1OCðOÞH þ hmð254 nmÞ ! products
PCR Inc.); COF /N standard (85%); He (99.99995%,
2
2
The parameter a is the yield of n-C F2n+1OC(O)H from
Takachiho Chemical Industry Co., Japan); and pure
O (99.99%, Nihon Sanso Corp., Japan).
n
the reaction of n-C F
OC(O)H with OH radicals
n
2n+1
3
2
(
from Eq. (I) [7]
a = 0 ꢀ 1). The values of a and k can be determined
6
3
. Results and discussion
3.1. Absorption cross-section of n-C F2n+1OC(O)H
n
a
y ¼ 1 h ꢀ
k6
ꢁi
J
ꢀ
1 þ
k5
k6½OHꢁav
ꢂ
ꢃ
2
ꢀ
ꢁ
3
ꢀ1
k
k
6
5
J
1
þk
½OHꢁ
av
The observed products of the OH radical-initiated oxi-
dation of C F OCH were C F OC(O)H, CF C(O)F,
and COF , and those for n-C F OCH were n-C F O
6
6
7
ꢂ ð1 ꢀ xÞ4ð1 ꢀ xÞ
ꢀ 15;
ðIÞ
2
5
3
2
5
3
2
3
7
3
3 7
C(O)H, C F C(O)F, and COF (Fig. 1). We did not
2
2
5
D½n ꢀ C
n
F
2nþ1OCH
3
ꢁt
determine CO in this study. C F OC(O)H and n-C F O
2 2 5 3 7
x ¼
;
½
n ꢀ C
n
F
2nþ1OCH
3
ꢁ
C(O)H were identified from their reported spectra [4,5].
For the reaction of C F OCH , because C F OC(O)H,
CF C(O)F, and COF were the only products that con-
0
½
n ꢀ C
n
F
2nþ1OCðOÞHꢁ
2
5
3
2 5
t
y ¼ ꢀ
;
3
2
½
n ꢀ C
n
F2nþ1OCH
3
ꢁ
0
tained both carbon and fluorine, we determined the e
ꢀ
19
where k and k are the rate constants for the reactions in
6
value for C F OC(O)H to be (5.20 ± 0.50) · 10
5
2
ꢀ1
5
2
cm molecule (base 10) at 1803 cm from the material
ꢀ1
Eqs. (5) and (6); J is the rate of photolysis of n-C F2n+1O
n
C(O)H (the J values of C F OC(O)H and n-C F O
2
balance equation D[C F OC(O)H] = D[C F OCH ] ꢀ
2 5
5
3
7
2
5
t
2
5
3 t
ꢀ
5
C(O)H were determined to be (1.88 ± 0.10) · 10 (two
[CF C(O)F] ꢀ [COF ] , where D[C F OCH ] = ([C F
3
t
2 t
2
5
3 t

L. Chen et al. / Chemical Physics Letters 400 (2004) 563–568
565
(
(
(
a) Before UV Irradiation
(d) Before UV Irradiation
b) After UV Irradiation
(e) After UV Irradiation
for 30 min
for 30 min
CF C(O)F
C F C(O)F
3
2 5
C F OC(O)H
COF2
2 5
COF2
n-C F OC(O)H
3
7
c) CF C(O)F
(f) C F C(O)F
2 5
3
2
000
1800
1600
1400
1200
1000
800 2000
1800
1600
1400
1200
-1
1000
800
-1
Wavelength (cm )
Wavelength (cm )
1
5
17
Fig. 1. IR spectra observed before and after 30-min irradiation of C
17
2
F
5
OCH
3
(1.01 · 10 )/H
2
O(5.6 · 10 ) (a) and (b), and n-C
3
F
7
OCH
3
1
5
(
1.01 · 10 )/H
2
O(5.6 · 10 ) (d) and (e) at 298 K in 200 Torr of He; reference spectra of CF
3
2 5
C(O)F (c) and C F C(O)F (f).
OCH ] ꢀ [C F OCH ] ) for the initial 18-min period.
ꢀ1
d½n ꢀ C
n
F
2nþ1OCH
3
ꢁ ;
3
0
2
5
3 t
½
OHꢁ ¼
t
The e value for n-C F OC(O)H was determined to be
k ½n-C F2nþ1OCH3ꢁt
dt
3
7
5
n
ꢀ
19
2
cm molecule (base 10) at 1803
ꢀ1
(
cm by the same method.
5.47 ± 0.57) · 10
ðIIÞ
ꢀ
1
Although a blank experiment indicated that the con-
centrations of CF C(O)F, C F C(O)F, and COF were
where [OH] and [n-C F
n
OCH ] are the concentra-
3 t
3
2
5
2
t
2n+1
reduced by photolysis and wall reaction in this system,
the losses of CF C(O)F, C F C(O)F, and COF were
tions of OH radicals and n-C F
n
OCH at reaction
2n+1 3
time t, and k is the rate constant for reaction (5).
5
3
2
5
2
<2%, <2%, and 2%, respectively, in the initial 18-min
Fig. 2 shows the plots of C F OCH and OH radical
2
5
3
period. Therefore, calculation of the e values for C F O-
concentration versus irradiation time. To derive the
value of d[C F OCH ]/dt at time t, the [C F OCH ]
2
5
C(O)H and n-C F OC(O)H from the data during the ini-
7
3
2
5
3
2
5
3
tial 18-min period was not affected by these losses.
Therefore, calculation of the e values for C F OC(O)H
vs. time data were fitted to a third-order polynomial,
and the function thus obtained was differentiated to ob-
tain d[C F OCH ]/dt. The OH radical concentration
2
5
and n-C F OC(O)H from the data during the initial
3
7
2
5
3
1
8-min period was not affected by these losses.
was nearly constant during irradiation. The average
1
0
OH radical concentration was (4.1 ± 0.8) · 10 radicals
ꢀ
cm . Over all the measurements of C F OC(O)H and
2 5
3
3
.2. Estimate of OH radical concentration
n-C F OC(O)H, the average OH radical concentration
3
7
1
0
ꢀ3
The concentration of OH radicals in the reaction
chamber was estimated from the decay rate of
n-C F OCH by means of Eq. (II).
range was (2.41–5.41) · 10 radicals cm . The varia-
tion of OH radical concentration was less than 30%
for each measurement.
n
2n+1
3

566
L. Chen et al. / Chemical Physics Letters 400 (2004) 563–568
ꢀ
14
3
cm molecule
ꢀ1 ꢀ1
10
1
5
5
4
4
4
4
10
1
1
8
6
4
2
.2x10
5x10
CH + OH) (298 K) = 1.21 · 10
3
s
ꢀ5
ꢀ1
at 298 K [3], J = 1.88 · 10
s
, and [OH]av = 4.1 · 10
OH
ꢀ3
1
radicals cm . Average a and k values of (0.99 ± 0.12)
1
.0x10
10
4
3
2
x10
x10
x10
ꢀ14
3
cm molecule s , respec-
ꢀ1 ꢀ1
and (1.50 ± 0.11) · 10
tively, were obtained from four runs. The plot of [n-
1
.0x10
10
10
10
C F OC(O)H] /[n-C F OCH ] versus D[n-C F O CH ] /
n-C F OCH ] at 298 K obtained was also shown in
3 7 3 0
3
7
t
3
7
3 0
3
7
3 t
[
1
C F OCH
3
.0x10
2
5
Fig. 3. The values of a and k were determined to be
2
ꢀ14
3
cm mole-
(0.99 ± 0.06) and (2.04 ± 0.14) · 10
1
ꢀ1 ꢀ1
.0x10
cule
random errors and represent precision only. Potential
s . The errors reported are ±2 SD, which are
1
1x10
.0x10
systematic errors to the k and k values might be from
2
1
the errors in the values of J, the average OH radical con-
centration, the values of the absorption cross-sections (e)
0
0
0
10 20 30 40 50 60 70 80
Irradiation time (min)
for n-C F
stants for n-C F
OC(O)H , and the values of the rate con-
OCH with OH radicals. The loss
3
n
2n+1
3
n
2n+1
of n-C F2n+1OC(O)H by photolysis was actually only
Fig. 2. Plots of C
2
F
5
OCH
3
and OH radical concentrations versus
n
irradiation time. The data were obtained from the experiment in Fig. 1.
The curves were obtained by fitting the data to a third-order
polynomial.
less than 5% of the loss by the OH reaction. The errors
for k and k due to the errors in the values of J (10%)
and the average OH radical concentration (30%) were
examined to be less than 3%. We examined the influence
1
2
3.3. Rate constants for the reaction of n-CnF2n+1OC(O)H
with OH radicals
of the errors in the e of n-C
of k , k , and, a in this method. The same values of k
and k , 10% change of a value, were obtained by varying
n
F2n+1OC(O)H to the values
1
2
1
2
Fig. 3 shows a plot of [C F OC(O)H] /[C F OCH ]
3 0
the value of e of n-C
errors in the e of n-C
to affect the values of k
tematic errors could add an additional 10% to the k
and k values with due consideration for the errors in
the rate constants of n-C with OH radicals.
The a values for C F OC(O)H and n-C F OC(O)H
n
F
2n+1OC(O)H with 10%. Thus, the
2n+1OC(O)H were not considered
and k . Finally, potential sys-
2
5
t
2
5
versus D[C F OCH ] /[C F OCH ] at 298 K. Fitting
F
n
2
5
3 t
2
5
3 0
the data for C F OCH and C F OCH in Fig. 3 to
2
1
2
5
3
2
5
3
Eq. (I) by means of a nonlinear least-squares analysis
gave a and k values of (0.98 ± 0.03) and (1.60 ± 0.06)
1
1
2
ꢀ
14
3
cm molecule
ꢀ1 ꢀ1
·
10
s
using
k
(C F O-
5
F2n+1OCH
n 3
2
2
5
3 7
showed that the yields of C F OC(O)H and n-C F O-
2
5
3 7
C(O)H were unity for the reactions of C F OCH and
3
2
5
0
0
0
.35
n-C F OCH with OH radicals, a result that is consist-
3
7
3
ent with the results of previous studies [4,5].
.30
.25
It is necessary to examine whether, and to what
extent, C F OCH , n-C F OCH , C F OC(O)H, and
n-C F OC(O)H are consumed in processes other than
2
5
3
3
7
3
2 5
3
7
2n+1
n
reaction with OH radicals and photolysis of C F O-
2 5
C(O)H and n-C F OC(O)H. Possible routes for loss of
3 7
n
0.20
t
these species are direct UV photolysis of C F OCH
3
2
5
1
and n-C F OCH , reactions with O( D) produced by
3
7
3
0
.15
.10
the photolysis of O , and the dark reaction.
3
When C F OCH or n-C F OCH was directly pho-
2
5
3
3
7
3
0
2
n
+
1
tolyzed by irradiation of
a
C F OCH (or n-
2
5
3
n
C F OC(O)H
2
5
C F OCH )/He gas mixture at 298 K for 5 h, no
3 7 3
n
0.05
0
change in C F OCH or n-C F OCH concentration
2 5 3 3 7 3
n-C F OC(O)H
3
7
was observed. The rate constants for reactions of or-
1
ꢀ10
ganic compounds with O( D) range from 10
to
[8]. By assuming that the
upper limit for the rate constants of the reactions of
0
0.2
0.4
0.6
0.8
1.0
ꢀ13
3
ꢀ1 ꢀ1
1
0
cm molecule s
∆
[n-C F OCH ]/[n-C F2n+1OCH3]0
n
2n+1
3 t
n
1
ꢀ10
3
ꢀ1 ꢀ1
reactants with O( D) was 2 · 10
we can estimate the reaction rate to be <2 · 10 s
which is 1/500 times the reaction rate of H O and O
cm molecule s
,
,
Fig. 3. Plot of [n-C
/[n-C
experiment in Fig. 1. The curve is a fit of Eq. (I) to the data for
n-C 2n+1OC(O)H] /[n-C and D[n-C /[n-
2n+1OCH
n
F
2n+1OC(O)H]
t
/[n-C
n
F2n+1OCH
3
]
0
versus D[n-
5
ꢀ1
C
n
F
2n+1OCH
3
]
t
n
F
3 0
2n+1OCH ] . The data were obtained from the
2
2
8
ꢀ1
(
>1.27 · 10 s ) in this system. Therefore, reactions
[
n
F
t
n
F
2n+1OCH
3
]
0
n 3 t
F2n+1OCH ]
1
of the HFEs with O( D) were insignificant.
C
n
F
3
]
0
.

L. Chen et al. / Chemical Physics Letters 400 (2004) 563–568
567
-14
5x10
The dark reactions of C F OCH , n-C F OCH ,
2
5
3
3
7
3
C F OC(O)H, and n-C F OC(O)H were investigated
3 7
2
5
C F OC(O)H
2
5
over a period of 5–6 h in the presence of the same con-
centration of water vapor as that used in the measure-
ment. No changes in C F OCH and n-C F OCH
3
n-C F OC(O)H
3
7
2
5
3
3
7
concentrations were observed, and the decay rates of
C F OC(O)H and n-C F OC(O)H were determined to
-14
2x10
2
5
3 7
ꢀ
6
ꢀ6 ꢀ1
be (3.1 ± 0.6) · 10 and (3.3 ± 0.6) · 10
tively. In the measurement, the irradiation time was less
s , respec-
than 2 h, and the decays of C F OC(O)H and n-C F
3 7
2
5
-14
1x10
OC(O)H were estimated to be less than 3% for a 2-h
irradiation period. Therefore, losses due to the dark
reactions of C F OCH , n-C F OCH , C F OC(O)H,
k
2
5
3
3
7
3
2 5
and n-C F OC(O)H were negligible.
3
7
-15
5x10
The a, k and k values were measured over the tem-
1
2
2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2
perature range 253–328 K. Plots of [n-C F
n
2n+1
-1
1
000/T (K )
OC(O)H] /[n-C F
t
OCH ] versus D[n-C F2n+1OCH3]t
3 0
n
2n+1
n
/
[n-C F
n
OCH ] could be fitted by Eq. (I), as could
3 0
2 5
Fig. 4. Arrhenius plots for the reactions of C F OC(O)H and
2n+1
the plot shown in Fig. 3. Values of a, k and k at vari-
3 7
n-C F OC(O)H with OH radicals.
1
2
ous temperatures are summarized in Table 1. Arrhenius
plots for k and k2 are shown in Fig. 4. Using
1
ꢀ
Ea=RT
k ¼ Ae
, we estimated the temperature dependences
ꢀ13
of k and k as (9.24 ± 1.33) · 10
exp[(ꢀ1230 ± 40)/T]
3.4. Atmospheric lifetime of n-CnF2n+1OC(O)H with
respect to reaction with OH radicals
1
2
ꢀ12
3
and (1.41 ± 0.26) · 10
exp[(ꢀ1260 ± 50)/T] cm mole-
ꢀ1
s from the nonlinear weighted least-squares
ꢀ
1
cule
analysis of the data in Fig. 4. The Arrhenius parameters
and the values of k and k at 298 K are listed in Table 2.
We estimated the atmospheric lifetimes of C F O
2
5
1
2
C(O)H and n-C F OC(O)H with respect to reaction
3 7
Table 1
Observed values of a, k
1
and k
2
at the temperature range of 253–328 K
[OH]av range
b
a
Compound Temp.
K)
328
k
(10
r
k
s
10
ꢀ3
ꢀ14
3
cm molecule
ꢀ1 ꢀ1 a
ꢀ14
3 ꢀ1 ꢀ1 b
cm molecule s )
(
(10 molecule cm
)
s
)
(10
C
2
F
5
OC(O)H
3.19–3.28
2.76–4.20
3.60–4.11
2.41–2.78
3.37–3.71
3.08–3.90
1.90
1.53
1.00 ± 0.03
1.00 ± 0.02
0.99 ± 0.12
1.00 ± 0.02
0.98 ± 0.02
0.96 ± 0.04
2.11 ± 0.11
1.82 ± 0.07
1.50 ± 0.11
1.19 ± 0.06
0.911 ± 0.052
0.712 ± 0.033
3
2
2
2
2
13
98
83
68
53
1.21
0.915
0.679
0.486
n-C
3
F
7
OC(O)H
328
2.94–3.10
3.64–3.83
4.31–5.41
3.91–4.61
3.47–4.92
3.98–5.13
1.88
1.50
0.99 ± 0.04
0.99 ± 0.06
0.99 ± 0.06
1.03 ± 0.04
1.00 ± 0.03
0.99 ± 0.04
2.95 ± 0.26
2.51 ± 0.12
2.04 ± 0.14
1.66 ± 0.16
1.20 ± 0.13
0.965 ± 0.053
3
2
2
2
2
13
98
83
68
53
1.17
0.892
0.658
0.468
a
Ref. [3].
b
The errors reported are ±2 SD. Potential systematic errors could add an additional 10% to the k
1
and k
2
values with due consideration for the
n 3
errors in the rate constants of n- F2n+1OCH with OH radicals.
Table 2
Arrhenius rate constant parameters for the OH radical reaction of C
2
F
5
OC(O)H and n-C
3
F
7
OC(O)H
a
E /R
Compound k (298 K)
1
A
(10
Temp. range
(K)
ꢀ14
3
cm molecule
ꢀ1 ꢀ1 a
ꢀ12
3
cm molecule
ꢀ1 ꢀ1 a
a
(
10
s
)
s
)
(K)
C
n-C F OC(O)H
2
F
5
OC(O)H
1.48 ± 0.06
2.04 ± 0.04
0.924 ± 0.133
1.41 ± 0.26
1230 ± 40
1260 ± 50
253–328
253–328
3 7
a
1 2
The errors reported are ±2 SD. Potential systematic errors could add an additional 10% to the k and k values with due consideration for the
n 3
errors in the rate constants of n-C F2n+1OCH
with OH radicals.

568
L. Chen et al. / Chemical Physics Letters 400 (2004) 563–568
with OH radicals to be 3.6 and 2.6 years, respectively, by
using Eq. (III) [9]
[3] K. Tokuhashi, A. Takahashi, M. Kaise, S. Kondo, A. Sekiya, S.
Yamashita, H. Ito, Int. J. Chem. Kinet. 31 (1999) 846.
[
4] Y. Ninomiya, M. Kawasaki, A. Guschin, L.T. Molina, M.J.
Molina, T.J. Wallington, Environ. Sci. Technol. 34 (2000)
2973.
k
3
CH CCl3
s
i
¼
ꢂ sCH CCl3
;
ðIIIÞ
3
k
i
[5] K. Nohara, M. Toma, S. Kutsuna, K. Takeuchi, T. Ibusuki,
Environ. Sci. Technol. 35 (2001) 114.
where s and s
(6.0 years [10]) represent the atmos-
CH CCl3
3
i
pheric lifetimes of n-C F
n
OC(O)H and CH CCl with
3
[6] L. Chen, S. Kutsuna, K. Tokuhashi, A. Sekiya, Int. J. Chem.
Kinet. 35 (2003) 317.
2n+1
3
respect to reaction with OH radicals, and k and k
i
CH CCl3
3
ꢀ15
3
cm molecule
ꢀ1 ꢀ1
[7] L. Chen, S. Kutsuna, K. Tokuhashi, A. Sekiya, Int. J. Chem.
Kinet. 36 (2004) 337.
(
constants for the reactions of n-C F2n+1OC(O)H and
6.0 · 10
s
[8]) represent the rate
n
[8] W.B. DeMore, S.P. Sander, D.M. Golden, R.F. Hampson, M.J.
Kurylo, C.J. Howard, A.R. Ravishankara, C.E. Kolb, M.J.
Molina, JPL Publ. 97-4, 1997.
CH CCl with OH radicals at 272 K. The k and k values
3
3
1
2
ꢀ
14
at 272 K were estimated to be 1.00 · 10
and
ꢀ
14
3
cm molecule
ꢀ1 ꢀ1
s , respectively.
[9] C.M. Spivakovsky, J.A. Logan, S.A. Montzka, Y.J.
Balkanski, M. Foreman-Fowler, D.B.A. Jones, L.W. Hor-
owitz, A.C. Fusco, C.A.M. Brenninkmeijer, M.J. Prather,
S.C. Wofsy, M.B. McElroy, J. Geophys. Res. 105 (2000)
1
.37 · 10
References
8
931.
[
10] R.G. Prinn, J. Huang, R.F. Weiss, D.M. Cunnold, P.J. Fraser,
P.G. Simmonds, A. McCulloch, C. Harth, P. Salameh, S.
OÕDoherty, R.H.J. Wang, L. Porter, B.R. Miller, Science 292
(2001) 1882.
[
[
1] A. Sekiya, S. Misaki, Chemtech 26 (1996) 44.
2] UNEP/WMO, Global Ozone Research and Monitoring Project:
Scientific Assessment of Ozone Depletion: Report No. 37, 1994.