Kinetics and mechanisms of the thermal gas-phase reactions of CF3OF and CF3OOCF3 with NO2

Article abstract of DOI:10.1524/zpch.1999.210.Part_1.083

The kinetics of the reactions of CF₃OF and CF₃OOCF₃ with NO₂ have been investigated using a conventional static system. The reaction between CF₃OF and NO₂ has been studied in a quartz reactor in the temperature range of 313.2-334.2 K, varying the initial pressure of CF₃OF between 19.4 and 165.2 Torr and that of NO₂ + N₂O₄ between 18.2 and 179.2 Torr. Some experiments were made in presence of 506.5-600.8 Torr of N₂. The total pressure had no influence on the reaction rate. COF₂ and FNO₂ were identified as reaction products. The expression obtained for the rate constant for the abstraction of fluorine atom from CF₃OF by NO₂ was: k₁ = (1.1±0.2) × 10⁹ exp(-16.4±1 kcal mol^-1/ RT) dm³ mol^-1 s^-1. The reaction of CF₃OOCF₃ with NO₂ has been studied in an aluminum reactor in the temperature range of 474.0-512.5 K, varying the initial pressure of CF₃OOCF₃ between 24.1 and 202.5 Torr and that of NO₂ between 24.7 and 202.7 Torr. Several experiments were made in presence of 399.8-490.5 Torr of N₂. The reaction rate was proportional to [CF₃OOCF₃]^1/2. The reaction approached the first order with respect to NO₂ at low pressure of NO₂. Increasing the pressure of NO₂, the ratio of the reaction rates increased more rapidly than the ratio of the corresponding concentrations of NO₂. Three products were formed: COF₂, FNO and O₂. The expression obtained for the rate constant for the abstraction of the fluorine atom from the radical CF₃O by NO₂ was: k₈ = (1.72±0.4) × 10⁹ exp(-10.8±1 kcal mol^-1/RT) dm³ mol^-1 s^-1. The mechanisms for both reactions were postulated. by Oldenbourg Wissenschaftsverlag, Muenchen.

Full text of DOI:10.1524/zpch.1999.210.Part_1.083

Zeitschrift für
©
Chemie, Bd. 210, S. 83-94 (1999)
Physikalische
by Oldenbourg Wissenschaftsverlag, München
Kinetics and Mechanisms
of the Thermal Gas-Phase Reactions
of
and CF3OOCF3 with N02
CF3OF
By J.
Czamowski
Instituto de
Fisicoquímicas Teóricas
y
Aplicadas,
Investigaciones
Sucursal 4, Casilla de Correo 16, 1900 La Plata, Argentina
(
Received November 18, 1997; accepted February 23, 1998)
I
Thermal reactions ICF3OFI CF3OOCF31N02
Gas-phase
The kinetics of the reactions of CF,OF and CF,OOCF, with NO, have been investigated
conventional static system.
The reaction between CF,OF and N02 has been stud-
the initial
using
a
ied in
a
quartz reactor in the temperature range of 313.2—334.2 K, varying
of CF,OF between 19.4 and 165.2 Torr and that of N02
+
N204
between 18.2
pressure
and 179.2 Torr. Some experiments were made in presence of
5
06.5—600.8 Torr of N2.
The total pressure had no influence on the reaction rate. COF2 and FNO, were
identified
abstraction of
mol"7
as reaction
The expression obtained for the rate constant for the
products.
fluorine atom from CF,OF
NO, was: k,
(1.1 ±0.2)X 10" exp(-16.4±l kcal
by
dm3 moL1
s
'. The reaction of CF,OOCF, with NO, has been studied in an aluminum
RT)
of
reactor in the temperature range of 474.0—512.5 K, varying
the initial
pressure
between 24.1 and 202.5 Torr and that of N02 between 24.7 and 202.7 Torr.
CFjOOCF,
Several experiments were made in presence of 399.8—490.5
Torr of N2. The reaction rate
with respect
was
to [CF,OOCF,]"2. The reaction approached the first order
proportional
to NO, at low pressure of NO,. Increasing the pressure of N02, the
ratio of the reaction
rates increased more rapidly than the ratio of the corresponding
concentrations of NO,.
Three products were formed: COF2, FNO and O,. The expression
obtained for the rate
constant for the abstraction of the fluorine atom from the radical CF,0 by N02
was:
=
X
10"
dm3moL'
s
\ The mechanisms
ks
(1.72±0.4)
exp(-10.8±l kcalmoL7/?7)
for both reactions were
postulated.
Introduction
The thermal reaction of CF3OF with N02 has
been
investigated previously
the
of 367.0—393.0 K, using Magnesium and
[
1] in the temperature range
Aluminum
as reaction vessels. The formation of FN02 and
cylinders
due to the homolytic cleavage of O—F bond in
the bimolecu-
radical
CF30',
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84
J. Czarnowski
lar reaction between
and
was
as a
CF3OF
N02,
postulated
primary process.
was obtained:
process
The
for the rate constant of this
following expression
kx
3.46
X
10s exp(-15.78+0.25 kcal moì 'IRT) dm3 mol1 s1.
It is well known that radicals
are formed in the unimolecular
CF30'
of CF3OOCF3 above 450 [2-4].
decomposition
In this work, the
studies of the thermal reaction of CF3OF
respective
with N02 in
a
reactor at 313.2-334.2 and that of CF3OOCF3 with
quartz
N02 in
an aluminum reactor at 474.0—512.5
K,
have been undertaken in
reactions
order to obtain more kinetic data on the
occurring in
elementary
these
systems.
Experimental
Both reactions were studied
using a
conventional static
system, allowing
The
measurements at constant volume and
pressure
was measured with
temperature.
pressure
a
and the
was main-
quartz spiral gauge
temperature
tained within ±0.1 K,
a
Lauda thermostat.
using
Infrared
absorbance
were recorded on
of this
a
Perkin-Elmer 325
The
spectra
accuracy
spectrometer.
is ±0.5% and the wavenumber
spectrometer
and resolution are ±0.02% and <0.5cirr',
respectively. The
accuracy
10
cm cell with barium fluoride windows was used.
All reactants were commercial
CF3OF was washed with 0.1
products.
NaOH and filtered at
air
[5]. CF3OOCF3 was
liquid
temperature
purified by
fractional condensation between 133 and 163 K. To free N02 from NO,
a
series of freeze-thaw
color due to N203
cycles was
carried out in
of
until the blue
presence
N02 was
02
purified by
that distilled between 193 and 233 K.
The
fractional
disappeared.
degassed
condensation, using the fraction
N2
was bubbled
98%
H2S04 and
through
coil at
analytical-grade
passed slowly
through a Pyrex
liquid air temperature.
a) Reaction of CF3OF with N02
2
8
were made at 313.2, 323.1, 334.2 K,
a
experiments
using spherical quartz
reaction vessel. The course of the reaction was fol-
the of the reactants after
certain time,
bulb of 270 cm3 as
lowed
a
a
by determining
consumption
,
cooling the reaction vessel with liquid air and separating the reaction
mixture
fractional condensation. The initial
of CF3OF was
pressure
by
varied between 19.4 and 165.2 Torr and that of N02
and 179.2 Torr. Some were made
+
N204 between 18.2
N2,
varying its pres-
experiments
sure within 506.5 and 600.8 Torr.
adding
b) Reaction of CF3OOCF3 with N02
were made at 474.0, 492.8 and 512.5 K. An aluminum
2
6
experiments
cyl-
inder with
a
volume of 380 cm3 and the diameter of
5
cm was used as
a
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Kinetics and Mechanisms of the Thermal Gas-Phase Reactions
85
reaction vessel. The course of the reaction was followed
function of time. The initial
the
CF3OOCF3
by measuring
pressure increase as a
of
pressure
was varied between 24.1 and 202.5 Torr and that of N02 between 24.7 and
2
02.7 Torr. Several
were
in presence of N2,
performed
experiments
varying
its
from 399.8 to 490.5 Torr.
pressure
Results and discussion
a) Reaction of CF3OF with N02
A
where
small
increase was observed
the reaction course.
and At the
pressure
was the
during
ApiAt,
increase
Ap
pressure
point by point
correspond-
reaction time, was constant
the course of each
but
ing
varied from 1.1
were identified
during
experiment,
Two
2
X
10-3 to 1.6
X
10 Torr/min for different
experiments.
COF2 and FN02. SiF4
increase were
their known IR spectra
:
products
by
was also detected. Its formation and the observed
pressure
ascribed to the
The very
was never observed.
of FN02 on the
wall.
heterogeneous decomposition
quartz
infrared
band of CF3OOCF3 at 1166 cm-1 [6, 7]
strong
absorption
For
the reaction mixture, the reaction vessel was cooled down
analyzing
to the
air
and the mixture
fractional conden-
liquid
temperature
separated by
sation. There were no volatile
at
air
The
compounds
liquid
temperature.
fraction volatile at 133
consisted of CF3OF, COF2, FN02 and SiF4. To
determine the concentration of CF3OF and COF2 in this fraction, infrared
calibration curves were constructed,
the
These
using
pure compounds.
curves allowed the conversion of the
intensities at 1942 and
respectively. The residue
absorption
1
1
285 cm to the
at 133
The
of COF2 and CF3OF,
pressures
N204.
data of 13
was N02
+
are summarized in the Table 1,
analytical
experiments
where
is the reaction time,
is the pressure increase, [Nx02>], where
Ap
1
or
is
to
+
and indices
i
and
f
initial and
2,
equal
[N02
N204]
data,
signify
From these
it can be
that
final, respectively.
deduced,
[CF3OF]consumed
[
COF2].
The formation of
indicated that some
must be reformed in the
SiF4
N02
course of the reaction, due to the
of the reaction
decomposition
product
on the
wall.
FN02
quartz
To
the
results obtained for the
following mechanism was proposed:
explain
experimental
temperature range
of 313.2—334.2 K, the
+
CF3OF
CF30'
+
N02
N02
CF3CV
FN02
(1)
2)
+
+
M
CF3ON02
+
M
(
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8
6
J. Czarnowski
N02. ([N,02J.
Table 1. Analytical data of 13 experiments of the reaction CF,OF
+
where
1
or 2, is equal to [NO,
+
N204])
Run
At
(min)
CF,OF, CF,OF, COF, [N,02J¡ [ ,02>], N2
Ap
(Torr) (Torr)
(
)
(Torr)
(Torr) (Torr)
(Torr)
(Torr)
2
2
2
2
1
4
7
8
1
4
7
1
3
4
313.2 183.6
313.2 183.9
313.2 185.65
1.1
0.3
1.7
0.6
2.9
2.6
0.6
1.5
0.9
0.3
1.5
0.2
0.1
60.1
36.5
160.8
165.2
31.0
31.5
99.3
39.9
43.9
59.5
23.5
39.4
99.8
49.0
26.0
151.4
160.5
18.3
10.9
10.7
9.6
4.6
12.4
12.4
10.3
17.7
11.9
9.8
99.9
176.6
31.7
30.5
102.4
102.4
29.8
60.9
60.0
39.8
78.3
19.1
84.6
160.7
20.3
24.6
89.6
89.1
10.9
32.8
40.5
22.0
61.9
10.0
5.7
507.1
506.5
313.2
323.1
323.1
323.1
76.9
184.3
182.5
177.0
19.1
88.8
22.0
31.9
49.7
12.5
34.5
92.9
550.2
1
1
1
1
1
1
334.2 196.75
334.2
334.2
93.1
89.3
549.8
600.8
5
7
8
334.2 131.6
334.2 137.35
11.2
5.1
6.9
334.2
90.3
18.2
—
+
FN02
CF,ON02
COF2
(3)
(4)
The lack of formation of
FN02=^SiF4 +
4N02.
4
The reaction (1) is the rate
determining step.
removed
CF3OOCF3 indicates that the radical CF,0' is
N02,
the
was
by
giving
adduct CF3ON02. The formation of the adduct at room temperature
other authors [8—12]. The adduct may
COF2
reported by
decompose giving
and FN02 [13, 14] or dissociate
CF,0' and N02. The experi-
reforming
mental results
work,
that within the temperature and
decomposes
range of this
suggest,
pressure
into COF, and FNO, rather than dissociates to
the adduct
reform radical CF30\
the
to the reaction scheme, rep-
Applying
steady-state approximation
resented
(1) —(4), the
reaction rate for consumption of
by Eqs.
CF3OF was obtained:
following
-
d
d
fc,[CF3OF][N02]
the following expression was used
[N02]f)
(I)
[
CF3OF]/dt
[COF2]/Jí
To calculate the rate constant
:
/
/
+
X
At)
k{
{In ([CF3OF]¡
[CF3OF]f)}
{1/2 ([NO,],
(II)
where
mixture [NO,
and [N02]f are the initial and final contents of N02 in the
[
N02]¡
+
N204], as calculated
the equilibrium constant [15].
are represented in the Table 2.
using
The rate constants k¡ of 26
experiments
In this table At is the reaction time, [Nx02J, where
1
or 2, is equal to
+
N204] and
indices
i
and
f
denote initial and final concentration,
[
N02
respectively.
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Kinetics and Mechanisms of the Thermal Gas-Phase Reactions
87
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88
J. Czarnowski
-3.0
-
6.0
2.9
3.0
3.1
3.2
3.3
(
3/ )/
Fig. 1. Arrhenius plot of k¡.
From this table it can be seen that the
consumption rate
of
is not
CF3OF
affected
the total
by
pressure.
The mean values of &i obtained at 313.2, 323.1 and 334.2
were
10"2dm3moF1
of the rate constant k1 can be
X
10
\
(9.74±0.6)
X
10'3 and (2.32±0.2)
X
(
4.46±0.4)
s_l, respectively.
The
temperature dependence
in the Arrhenius form
1), as follows:
(Fig.
expressed
(1.1±0.2) X 109exp(-16.4±l
obtained
kcal
moV'IRT) dm3 mol"1
for k, in
[1] was:
previously
s"1.
k,
The
( )
Mg reactor
dm3 mol"1 s"1
expression
k,
3.46X108 exp (-15.78±0.25
kcal
mol"l/RT)
The difference between the two
for kx is ascribed to the
expressions
and
of some radicals CF30' on the wall of the
adsorption
decomposition
reactor.
Mg
Reaction of
with N02
CF3OOCF,
b)
The reaction
with
root of
to N02 at low
a
increase and its rate was
The reaction
proceeded
square
pressure
pro-
the
to the
first order with
portional
[CF3OOCF3].
approached
of N02.
the
than the
were COF2,
respect
pressure
Increasing
pres-
sure of N02 the ratio of the reaction rates increased more
rapidly
ratio of the
concentrations of N02. The
corresponding
products
FNO and 02. Traces of FN02 were also observed.
For
sel was
residual mixture was
the reaction mixture of the
the reaction ves-
and 02 evacuated. The
fractional condensation
analyzing
experiments,
cooled to the
air
rapidly
liquid
temperature
by
in three fractions
separated
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Kinetics and Mechanisms of the Thermal Gas-Phase Reactions
Table 3. Analytical data of
experiments of reaction CF,OOCF,
89
5
+
NO,.
Run
Ap
At
CF,OOCF(i CF,OOCF„ COF2 N02¡
02
02f
(
)
(Torr) (Ton)
(Ton)
(Ton)
(Ton) (Ton) (Ton) (Ton)
3
9
1
5
2
474.0 21.2
474.0 47.2
474.0 47.1
492.8 33.5
512.5 21.8
244.55 102.5
91.9
27.4
179.0
87.4
21.5
46.9
46.9
33.5
21.8
51.0
202.3
199.3
50.0
29.6 10.5
155.3 23.6
152.2 23.7
107.25
50.5
135.5
51.2
202.5
104.0
1
1
2
16.3
37.1
16.8
10.7
13.95 102.9
91.9
58.8
at 133 and 173 K. The fraction volatile at 133
consisted of COF2 and
FNO, identified by their known
IR
The concentration of
COF2
in
spectra.
this fraction was determined
the
constructed infrared cali-
using
previously
bration curve, which allowed the conversion of IR
intensities at
absorption
1
942 cm"1 to
of COF2. CF3OOCF3 distilled as volatile between
pressures
1
4
33 and 173 K. N02 remained as
a
residue. At the
of
no
temperature range
74.0-512.5 K, the dissociation
of N204 is so
high that
equilibrium
corrections were made for the N02 content.
The
data of
5
are summarized in the Table 3. In
analytical
experiments
this table
and
that
is the
increase, At is the reaction time and indices
i
Ap
pressure
final, respectively.
[CF3OOCF3]
[NO,] [COF2]
results obtained in the
f
denote initial
A
From these data it can be deduced
y
2
2
[
QJ.
To
the
the
of
explain
experimental
temperature range
postulated:
474.0—512.5
mechanism was
following
+
—
CF3OOCF3
CF30'
CF30'
(5)
(6)
(7)
(8)
(9)
+
+
M
+
M
CF30'
N02
—
CF3ONO,
(F(NO,))*
+
CF3ON02
COF2
—
+
CF30'
CF30"
+
N02
COF,
(F(N02))*
+
CF30"
—
CF3OOCF3
a'"mmumwa".
FNO
+
1/2 02.
(10)
(F(N02))*
In the
of 474.0—512.5 K, the
is the
temperature range
primary process
of CF3OOCF3
N02 has two
two radicals
[2—4]. The reac-
channels: the ad-
other au-
decomposition
giving
CF30'
tion
+
CF30"
thermochemically possible
dition or the abstraction of the fluorine atom. It was
reported by
thors [9] that, at room
the addition reaction is the dominant
temperature,
one, being >90% of the CF30' consumed via this reaction to give CF3ONO,.
As
traces of FN02 were observed and the main
nitrogen containing
only
detected was FNO, the formation of the latter was ascribed to the
product
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90
J. Czarnowski
Table 4.
N"
4
of the reaction CF,OOCF,
+
NO,. (T 474.0 K, CF,OOCF,
Experiment
24.1 Torr, N02
202.6 Torr,
5.0
x
IO 3).
ß
k'xW
(Torr""2 min"1)
(min)
(Torr)
5
.6
2.5
4.5
6.4
1.14
1.12
1.14
1.16
1.21
1.17
1.21
1.15
1.17
1.15
1.07
1.07
1
1
0.35
5.0
2
2
3
4
6
7
9
1
1
2.0
9.6
8.85
8.9
2.1
6.6
8.3
18.9
79.7
9.2
12.2
15.5
18.9
22.8
26.7
31.7
35.4
43.5
Table 5. Experiment
01.9 Torr, NO,
"
8
of the reaction CFìOOCF,
+
NO,. (T 474.0 K, CF,OOCF,
401.2 Torr).
1
24.7 Torr,
5.0
x
10
,
ß
rxio4
(Torr""2 min"1)
(Torr)
(min)
1
5
7.7
6.2
86.4
1.2
3.4
9.4
11.6
13.3
14.9
1.25
1.14
1.16
1.16
1.11
1.18
1
2
3
49.8
09.8
72.1
3
Table 6.
CF,OOCF,
N" 11 of the reaction CF,OOCF,
+
NO,. (T
474.0 K,
Experiment
202.5 Torr, N02
199.3 Torr,
5.0
x
IO"3).
ß
rxlO4
(Torr""2 min"')
(min)
(Torr)
2
.6
3.1
6.2
1.07
0.994
1.07
1.09
1.03
1.04
1.07
1.05
1.01
5.65
1
2.5
13.8
17.5
20.6
24.7
28.4
32.2
36.5
39.8
43.2
47.1
15.95
1
9.1
2
2
3
3
4
4
5
3.4
7.3
1.5
6.7
0.9
5.3
0.5
0.997
1.01
1.02
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Kinetics and Mechanisms of the Thermal Gas-Phase Reactions
Table 7. Experiment N° 15 of the reaction CF,OOCF,
91
+
NO,. (T
492.8 K,
CF,OOCF,
104.0 Torr, NO,
50.0 Torr,
ß
3.1
X
IO"3).
k'XW"2
(Torr
(min)
(Torr)
min ')
4
8
.4
.9
2.0
4.1
7.5
12.4
15.9
18.4
21.4
25.0
27.5
32.9
3.96
4.29
4.25
4.13
4.41
4.13
4.43
4.23
4.53
4.09
16.8
2
4
4
5
7
8
9.95
0.05
8.6
9.2
4.4
5.75
1
19.1
reaction of the excited (FONO)* on the Aluminum reactor
heterogeneous
wall. The
of FONO into FNO and
atom was
decomposition
oxygen
postu-
lated as one of the
The
channels for the
of FONO [16].
possible
decomposition
found
of the rate constant for the con-
experimentally
dependence
of CF3OOCF3 on [CF3OOCF3]1/2 indicated that in the
sumption
temperature
to reform
of this work, the
of the reaction
is
(6) displaced
range
equilibrium
the radicals
which associate
reforming
CF3OOCF3.
CF30",
the
to the reaction scheme,
rep-
Applying
steady-state approximation
resented
(5)
and
the concentration of radicals
by Eqs.
—(10),
taking
the
CF30'
to (k5/2
following expression for the consump-
+
equal
&9)1/2[CF3OOCF3]"2
tion rate of CF3OOCF3 was obtained:
-d
/
dt
[
CF3OOCF3]
k&(k5/2 Â:9)1/2[CF3OOCF3]1/2[N02]{Â:6//t8[M]
1}
(IV)
where
y6[N2]
M
+
+
+
+
+
y,[N02]
y2[CF3OOCF3]
y3[COF2]
yJFNO]
efficiency
that
y5[02]
and y,_6 are the
collisional deactivation
factors.
and
of N02,
respective
the effect of N02 was observed,
>
Only
indicating
y,
y2_6
M
To determine the effect of collisional
y,[N02].
(IV) was transformed in y
efficiency
where
y
the
k'
+
Eq.
k'ikJk^M.,
{
(d [CF3OOCF3]/í/í)/([CF3OOCF3],/2[N02])} and k'= k¿kJ2 k9Y'\ Plotting
as a
function of
[N02], a straight
line was obtained and
the obtained value of the
was
y
ß
{kjk^y^
derived from the
stants fc'were
con-
slope. Using
ß,
composite
for each
computed, point by point,
experiment.
The courses of five
N° 4, 8, 11, 15 and 22, are
typical experiments,
illustrated in the Tables 4, 5, 6,
7
and 8,
pressure
In these tables
is
respectively.
the reaction time and is the
increase.
The mean rate constants /c'and for 21
the Table 9. In this table the index
are
in
ß
experiments
represented
i means initial.
Unauthenticated
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9
2
J. Czarnowski
NO,. (T 512.5 K,
Table 8. Experiment N° 22 of the reaction CF^OCF,
+
102.9 Torr, NO,
58.8 Torr,
2.1
X
IO"3).
CF,OOCF.,
ß
k'xW
(Torr""2 min"1)
(Torr)
(min)
1
.7
3.3
7.3
11.4
14.9
18.3
21.8
1.50
1.46
1.52
1.62
1.72
1.42
4.0
6.5
8.7
1
1
0.9
3.95
Table 9. The mean constants k'and for 21
ß
of the reaction CF.,OOCF,
experiments
NO, at different temperatures.
Run
CF^OOCF-m
(Torr)
NO,,
(Torr)
ß
10'
N2
(Torr)
k'XW
(Torr""2 min"1)
(K)
3
474.0
474.0
474.0
474.0
474.0
474.0
474.0
474.0
474.0
474.0
474.0
492.8
492.8
492.8
492.8
492.8
512.5
512.5
512.5
512.5
512.5
102.5
24.1
200.1
101.5
103.0
101.9
51.2
24.7
202.5
103.2
101.1
104.0
201.2
25.8
24.8
50.4
102.9
24.8
101.8
100.6
50.2
51.0
202.6
26.0
101.9
201.1
24.7
202.3
202.7
199.3
50.5
51.5
50.0
25.2
198.6
100.3
25.8
58.8
102.0
25.6
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
5.0
3.1
3.1
3.1
3.1
3.1
2.1
2.1
2.1
2.1
2.1
0.933
1.15
1.42
0.946
1.02
1.17
1.08
1.16
1.04
0.994
0.979
4.25
4.35
4.12
4.27
4.27
15.4
16.9
15.0
14.5
4
5
6
7
8
9
401.2
402.3
1
1
1
1
1
0
1
2
3
5
399.8
16
17
18
19
490.5
402.8
2
2
2
2
2
3
4
5
25.2
101.5
26
15.6
The values of (1.08±0.1)
X
10 4, (4.25
10"4 and (1.55 ±0.1)
±
0.4)
X10"3 Torr ^min-1 were obtained for k' at 474.0, 492.8 and 512.5 K,
respectively.
In order to derive k8 from k'=
k9)U2, the calculated value for k9 of
ks(k5/2
and k5 was
IO10 dm3 mol-1 s-1 was used
from the
[
17]
computed
expression
obtained
[3]
:
previously
(1.26±0.45)X
1016
exp(-46.3±0.4 kcal mol"VRT)
s1.
ks
Unauthenticated
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Kinetics and Mechanisms of the Thermal Gas-Phase Reactions
93
10.7
f
1.9
2.0
2.1
2.2
(io3A)
/
Fig. 2. Arrhenius plot of ks.
The values of (1.75±0.4)X IO4, (2.83±0.6) 104 and (4.29±0.6) 104
dm3 mol"1 s"1 were obtained for kg at 474, 492.8 and 512.5
K, respectively.
of the rate constant ks for the abstraction of
The
temperature dependence
fluorine atom from
follows:
N02 can be
in Arrhenius form
CF30' by
expressed
Fig. 2) as
(
ks
(1.72±0.4)X109 exp(-10.8±l kcal mol VRT) dm3 mol"1 s"1.
Acknowledgement
The author thanks Mr Z. Czarnowski for
was
This work
Investigaciones
comments.
Nacional de
very helpful
financially supported by the Consejo
Científicas Técnicas.
y
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