Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study

Article abstract of DOI:10.1002/1097-4601(200103)33:3<191::AID-KIN1013>3.0.CO;2-8

The thermal dehydrochlorination CCl₂FCH₃→CClF double bond CH₂+HCl has been studied in a static system between 610 and 700 K at pressures ranging from 14 to 120 torr. The experiments were performed in the absence and presence of an added inhibitor (0.5 to 7 torr of C₃H₆) or catalyst (2 to 8 torr of CCl₄). The evolution of the reaction was followed by measuring the pressure rise in the quartz reaction vessel and analyzing the products by gas chromatography. All the experimental results can be explained quantitatively in terms of a reaction model both radical and molecular. The molecular dehydrochlorination has an activation energy of 52.05 kcal/mol and a preexponential factor of 10^14.02 s^-1.

Full text of DOI:10.1002/1097-4601(200103)33:3<191::AID-KIN1013>3.0.CO;2-8

Pyrolysis of 1,1-Dichloro-
-Fluoroethane in the
1
Absence and Presence of
Added Propene or CCl4:
A Computer-Aided Kinetic
Study
G. HUYBRECHTS, K. EERDEKENS
Laboratorium voor Fysische Scheikunde en Polymeren, Vrije Universiteit Brussel, 1050 Brussels, Belgium
Received 13 June 2000; accepted 13 October 2000
ABSTRACT: The thermal dehydrochlorination CCl FCH : CClF"CH ϩ HCl has been studied
2
3
2
in a static system between 610 and 700 K at pressures ranging from 14 to 120 torr. The
experiments were performed in the absence and presence of an added inhibitor (0.5 to 7 torr
of C H ) or catalyst (2 to 8 torr of CCl ). The evolution of the reaction was followed by measuring
3
6
4
the pressure rise in the quartz reaction vessel and analyzing the products by gas chromatog-
raphy. All the experimental results can be explained quantitatively in terms of a reaction model
both radical and molecular. The molecular dehydrochlorination has an activation energy of
7.05 kcal/mol and a preexponential factor of 1014.02 s . ꢀ 2001 John Wiley & Sons, Inc. Int J Chem
Ϫ1
5
Kinet 33: 191–197, 2001
INTRODUCTION
though the inhibitory effect of added NO they mea-
sured was weak.
Kinetic and mechanistic studies in our laboratory have
shown that the thermal dehydrochlorination of
CCl CH is mainly a radical reaction [1], while that of
It seemed, therefore, interesting to us to reinvesti-
gate the reaction in the same conditions as those pre-
viously used in the cases of CCl CH3 [1] and
3
3
3
CClF CH is molecular [2,3]. This work deals with the
CClF CH3 [2,5]. The experiments were thus per-
2
3
2
intermediate case of CCl FCH (Freon 141b), which
formed in the same conditioned quartz static reaction
vessel in the absence and presence of added C H or
2
3
completes the series CCl3ϪnFnCH , with n ϭ 0–2.
3
3
6
Sianesi et al. [4] studied the elimination of HCl
from CCl FCH in a Pt tubular reactor between 803
CCl4.
2
3
and 853 K at pressures ranging from 100 to 760 torr.
These authors observed first-order kinetics with an ac-
tivation energy of only 47 kcal/mol. They attributed
this low value to a predominant radical pathway, al-
EXPERIMENTAL
CCl FCH (Solvay), propene (Messer-Griesheim),and
2
3
CCl (UCB), 99.95, 99.98, and 99.997% pure, respec-
Correspondence to: G. Huybrechts (ghuybrec@vub.ac.be)
4
ꢀ
2001 John Wiley & Sons, Inc.
tively, were used without further purification.

1
92
HUYBRECHTS AND EERDEKENS
1
The pyrolysis of CCl FCH was followed by mea-
initiation (2), the chain propagations (3) and (4) and
2
3
suring the variation of the total pressure with a Pyrex
Bourdon gauge. The conventional static system, the
cylindrical quartz reaction cell (surface-to-volume ra-
their reverses, the radical transfer reactions (5) and (6)
and their back reactions, and the chain terminations
(Ϫ2), (7), and (8), the last one being heterogeneous.
Ϫ
1
tio S/V of about 1.2 cm , V ϭ 100 mL), and the tech-
nique were the same as in the previous studies of the
pyrolyses of CCl CH [1] and CClF CH [2,5]. The
When CCl is added, the chain initiation (2) is re-
4
placed by the faster step (9) followed by the transfer
steps (10) to (12) and their reverses, and the chain
terminations become the radical recombinations (Ϫ9),
(13), and (14).
3
3
2
3
reactor walls were conditioned by pyrolyzing several
times large amounts of CCl FCH at high temperature
2
3
(
723 K). The GC-analyses of the reaction products
Steps (Ϫ1), (Ϫ3), (Ϫ11), and (Ϫ13) are minor re-
actions for all experimental conditions used in this
work.
were performed on a 2-m column of 25% w/w Silicone
OV101 on 60–80 mesh ChromosorbPAW at 60 ꢁC.
More than 100 experiments were carried out. The
analyses showed that, in the absence and presence of
The reduction procedure involved a set of seven
typical experiments (three in the absence and four in
the presence of added C H or CCl ), with reaction
added propene or CCl , 1-chloro-1-fluoroethene and
4
3
6
4
1
,1-dichloroethene are formed according to the par-
conversions going up to about 20%. All their points
are shown in the figures given later, together with the
allel reactions
CClF"CH concentration-time profiles optimized by
2
means of OPTKIN. The corrections that were applied
to the initial values of the kinetic and thermodynamic
parameters to obtain these profiles are given in Tables
I and II, respectively. As can be seen, their values are
small. They are less than 0.6 kcal/mol for activation
energies and 0.2 log units for A-factors. The maximum
corrections on heats of formation and entropies
amount to Ϫ0.6 kcal/mol and 0.89 cal/mol K, respec-
tively.
CCl FCH !: CClF"CH ϩ HCl
(1)
2
3
2
and
CCl FCH !: CCl "CH ϩ HF
(2)
2
3
2
2
No other products are detected. The dehydrochlori-
nation (1) yields reproducible results but not the de-
hydrofluorination (2). The latter reaction, which is
about 10 times slower than the former (100 times when
CCl is added), is most probably heterogeneous (see
later) and has not been studied. The CClF"CH con-
RESULTS AND DISCUSSION
Pyrolysis of CCl FCH
4
2
2
3
centration-time profile of the dehydrochlorination was
obtained from the pressure rise in the reaction vessel
corrected for the small contribution of the dehydro-
fluorination. It also appears from the analyses that the
added C H and CCl are hardly consumed in the
The dehydrochlorination of CCl FCH has been stud-
2
3
ied between 650 and 700 K. The pressure ranged from
4 to 120 torr. Figures 1 and 2 show typical CClF"
1
CH concentration-time profiles for different temper-
2
3
6
4
atures and pressures. As can be seen, the reaction ob-
served, which is only slightly faster than the molecular
reaction at the beginning, accelerates markedly with
time and is well described by the optimized model
given in Table I. Note that the initial model already
yields reasonable results (see Fig. 1).
course of the reaction.
NUMERICAL MODELING OF THE
EXPERIMENTAL RESULTS
Analyses of the rates of the elementary reaction
steps show that the autoacceleration actually results
mainly from the radical step (6). This reaction converts
The numerical modeling procedure is similar to that
given in [1,5–7]. The molecular and radical reaction
model used is based on that for the pyrolyses of
CCl CH [1] and CClF CH [5]. The Arrhenius param-
eters, E and A, are either known or estimated; this also
holds for the thermochemical parameters used to cal-
culate E and A for back reactions from the “principle
of microscopic reversibility.” Using OPTKIN [8], this
reaction model could be reduced, by repeated simu-
lations and optimizations, to the reaction steps and the
parameters given in Tables I and II. The steps are the
molecular reactions (1) and (Ϫ1), the radical chain
the unreactive DCClFCH radicals (formed in the ini-
3
3
3
2
3
tiation step (2) and in the transfer step (5)) into Cl
chain carriers due to the HCl produced by the molec-
1
The C9Cl BDE in CFCl CH calculated from Table II is 79
2
3
kcal/mol. This value is much lower than values for other BDEs in
this molecule obtained from Table II, [1], [14], and [20]: These
values are 93, 103, and 113 kcal/mol for the C9C, C9H, and
C9F bonds, respectively. Reaction (2) is therefore likely the pri-
mary initiation step for radical formation.

PYROLYSIS OF 1,1-DICHLORO-1-FLUOROETHANE
193
Table I Kinetic Model for the Pyrolysis of CCl FCH3a
2
E
log A
10
Initial
Optim.
Corr.
0.05
Initial
Optim.
Corr.
a. Molecular reaction
1
57.00b
37.50c
57.05
38.17
14.00b
7.74c
14.02
7.94
0.02
CCl FCH ERF CClF"CH ϩ HCl
2
Ϫ1
2
3
b. Radical reactions
2
77.53c
0.00d
76.52
0.00
15.84c
10.30d
16.00
10.35
CCl FCH E
R
F DCClFCH ϩ Cl
2
3
3
Ϫ2
—
0.05
3
4.37e
4.84c
4.82
6.48
0.45
9.26e
7.69c
9.09
7.81
Ϫ0.17
Cl ϩ CCl FCH E
R
F CCl FCH D ϩ HCl
2
3
2
2
Ϫ3
4
19.97c
0.00f
20.54
0.00
14.89c
10.20f
15.15
10.37
CCl FCH D E
RF CClF"CH ϩ Cl
2
Ϫ4
2
2
—
0.17
0.19
5
22.05c
2.00g
20.77
1.74
10.51c
8.80g
10.81
8.99
Cl ϩ CCl FCH E
R
F DCClFCH ϩ Cl2
2
3
3
Ϫ5
Ϫ0.26
6
9.35c
2.48h
10.02
3.07
8.43c
10.00h
8.09
9.95
DCClFCH ϩ HCl E
RF CHClFCH ϩ Cl
3
Ϫ6
3
0.59
—
Ϫ0.05
Ϫ0.07
0.14
7
0.00d
0.00
9.30d
9.23
0.02
2
DCClFCH 9
9: product(s)
3
8
Ϫ0.08i
Ϫ0.28
Ϫ0.20
Ϫ0.12i
Cl ϩ wall 99 : Cl-wall
c. Additional radical reactions when CCl is added
4
9
67.91c
0.00j
68.17
0.00
16.77c
10.86j
16.84
10.76
CCl E
R
F CCl D ϩ Cl
4
3
Ϫ9
—
Ϫ0.10
1
0
15.52c
5.10j
15.69
5.00
10.78c
8.70j
11.09
8.83
Cl ϩ CCl E
R
F CCl D ϩ Cl2
4
3
Ϫ10
Ϫ0.10
0.13
1
1
19.00k
11.24c
19.23
13.37
0.23
8.99k
8.82c
8.97
9.08
Ϫ0.02
CCl D ϩ CCl FCH E F CCl H ϩ CCl FCH D
R
3
2
3
3
2
2
Ϫ11
1
2
11.53c
3.30l
10.88
3.37
8.41c
9.80l
8.49
9.89
CCl D ϩ HCl E
RF CCl H ϩ Cl
3
Ϫ12
3
0.07
—
0.09
0.04
13
0.00j
66.73c
0.00
9.67j
17.27c
9.71
2
CCl D E
RF C Cl
2 6
Ϫ13
3
67.07
17.58
1
4
0.00d
0.00
—
9.30d
9.27
Ϫ0.03
CCl D ϩ DCClFCH 99 : product(s)
3
3
a
The activation energies E are expressed in kcal/mol and the preexponential factors A in L, mol, and s-units: the values given below the
lines are for back reactions. Initial and Optim. are values before and after optimization, respectively. Correction Corr. ϭ Optim. Ϫ Initial.
When a dash (—) is given for Corr., the corresponding parameter was held constant during the optimization.
b
Experimental value obtained by means of OPTKIN from the data of this work concerning only the experiments with added propene.
Calculated in the computer program from the thermodynamic data given in Table II and the rate constant of the back reaction at the mean
c
temperature of all experiments.
d
Experimental data for the recombination reaction between Cl atoms and halogenated radicals are very scarce. It is, however, generally
1
0.3
accepted that these reactions occur with zero activation energy and a preexponential factor of 10 L/mol.s [1].
Recombination reactions between two halogenated alkyl radicals are expected to proceed slower. The value for the preexponential factor
9.3
and the rate constant is estimated at 10 L/mol.s [9].
e
Experimental value from [10].
f
Assumed to be equal to the value for Cl ϩ CF ϭ CH : CClF CH D from [11], derived from fitting to a mechanism.
2
2
2
2
g
h
i
Estimated from Arrhenius parameters for similar reactions.
Experimental value from [12].
Value determined in [5] for the reactor used in this work.
Value derived from fitting to a mechanism in [6].
j
k
l
Assumed to be equal to the value for CCl D ϩ CClF CH : CCl H ϩ CClF CH D proposed in [2].
3
2
3
3
2
2
Experimental value from [13].

1
94
HUYBRECHTS AND EERDEKENS
2
Table II Enthalpies of Formation ⌬Hꢁ (kcal/mol), Heat Capacities Cꢁ ϭ a ϩ bT ϩ cT , and Entropies Sꢁ (Gibbs/mol)
f
pT
Based on a 1-Atm Standard Statea
⌬
Hꢁ
Sꢁ
298
Cꢁ
p,T
f,298
2
5
Compound
Cl
Initial
Corr.
Initial
Corr.
a
10 ·b
10 ·c
29.0b
18.0c
—
0.12
Ϫ0.43
Ϫ0.60
—
39.5b
71.2c
—
0.60
0.89
Ϫ0.89
—
4.72
9.87
4.32
9.5
7.07
7.19
7.49
12.80
7.32
12.50
19.90
5.69
0.225
2.24
4.35
Ϫ0.179b
Ϫ1.41
Ϫ1.44
Ϫ1.11
Ϫ0.25b
0.161h
Ϫ1.73i
Ϫ1.93
Ϫ1.44k
b
CCl3 ·
CClFCH3
CCl FCH ·
d
e
f
·
Ϫ30.2
68.8
74.4
Ϫ29.7g
f
3.98
f
2
2
Cl2
HCl
0.0b
53.3b
0.426
Ϫ0.114
3.12
3.00
4.35
3.98
5.35
3.82
h
h
Ϫ22.1
—
44.7
70.6
73.8
—
0.59
Ϫ24.6i
Ϫ0.60
Ϫ0.15
Ϫ0.35
0.59
Ϫ0.11
Ϫ0.03
i
CCl H
3
c
c
b
CCl4
CHClFCH3
Ϫ22.2
Ϫ0.19
Ϫ0.45
0.39
Ϫ0.04
Ϫ0.47
Ϫ74.9j
Ϫ80.8j
65.8k
k
k
CCl FCH3
71.4
95.2
67.4
Ϫ1.11
Ϫ3.32
Ϫ1.87l
2
c
c
c
CCl CCl3
Ϫ33.2
3
Ϫ36.9l
l
CClF"CH2
a
Initial and Optim. are values before and after optimization, respectively. Correction Corr. ϭ Optim. Ϫ Initial. When a dash (—) is given
for Corr., the corresponding parameter was held constant during the optimization.
b
From JANAF thermochemical tables [14].
Value derived from fitting to a mechanism in [6] and [7].
Estimated value which corresponds to a value of the C9Cl bond dissociation energy for CCl FCH lying between the values for CCl CH
3
c
d
2
3
3
and CClF CH , calculated from data given in [1] and [3], respectively.
2
3
e
Estimated value that corresponds to a value of the preexponential factor for step (2) (see Table I) lying between those for the cases of
CCl CH [1] and CClF CH [3].
3
3
2
3
f
Value for a radical R estimated from the value for the corresponding molecule RH from this table.
g
Obtained from an interpolation of C9H bond dissociation energies for CCl CH and CClF CH , calculated from data given in [1] and
3
3
2
3
[
3], respecitvely.
h
Critical evaluation in [15].
Critical evaluation in [16].
Estimated value from [17].
i
j
k
l
Estimated by means of Yoneda’s method (see [18]) from the value for CClF CH estimated in [5].
2
3
Estimated from database in [19].
ular reaction (1) and the radical reaction (3) (see Table
I). The concentration of the Cl atoms thus increases
rapidly with time and hence also the rate of the radical
chain propagation (3), while the concentration of the
unreactive radicals decreases (see, e.g., Fig. 3). The
amounts of Cl and CHClFCH , produced by steps (5)
2
3
and (6), respectively, are more than a thousand times
lower than that of the main product CClF"CH . Nev-
2
ertheless, these steps are quite quickly close to reach-
ing a steady state of quasiequilibrium. Therefore, as
can be seen from Figure 3, the unreactive radicals re-
main the most abundant. This figure also shows that
the concentration of the CCl FCH D radicals is so low
2
2
that these chain carriers would not be involved in chain
termination steps even if “fall-off” effects would sig-
nificantly decrease their dissociation rate in step (4).
The small influence of the rate parameters of this chain
propagation step is confirmed by sensitivity analyses
as a function of reaction time. These analyses were
performed with OPTKIN using the model from Table
I completed with all possible chain terminations in-
Figure 1 Pyrolysis of 14.4 torr CCl FCH at 697.8 K. Con-
2
3
centration C of CClF"CH vs. reaction time t. (•)—Ex-
2
perimental; (Full and dotted curves)—Simulations using op-
timized and initial Arrhenius parameters from Table I,
respectively; (Dashed curve)—Simulation using only the
molecular reaction (1) and its optimized Arrhenius param-
eters from Table I.

PYROLYSIS OF 1,1-DICHLORO-1-FLUOROETHANE
195
Figure 2 Pyrolysis CCl FCH . Concentration C of CClF
2
3
Figure 4 Pyrolysis of 200 torr CCl FCH at 803 K. Con-
2
3
"
CH vs. reaction time t. (•)—Temperature ϭ 654.0 K and
2
centration C of CClF"CH vs. reaction time t. (•)—Cal-
2
initial pressure of CCl FCH ϭ 107.0 torr; (ꢂ)—Tempera-
2
3
culated from experiments in [4]; (Full curve)—Simulation
using optimized Arrhenius parameters from Table I; and
ture ϭ 696.2 K and initial pressure of CCl FCH ϭ 53.0
2
3
torr; (Full curves)—Simulations using optimized Arrhenius
parameters from Table I; and (Dashed curves)—Simulations
using only the molecular reaction (1) and its optimized Ar-
rhenius parameters from Table I.
(Dashed curve)—Simulation using only the molecular re-
action (1) and its optimized Arrhenius parameters from Ta-
ble I.
chain termination steps. Note also that the sensitivity
volving the CCl FCH D radicals. For example, they
2
2
coefficient for a possible isomerization of DCClFCH
3
reveal that for the experiment at 696.2 K from Figure
radicals to CClFHCH D radicals by H atom migration
2
2
, the reduced sensitivity coefficient Ѩ(ln[CClF"
is very low.2
CH ])/Ѩ(ln(rate constant)) for step (4) is about a hun-
2
Further support for the optimized molecular-radical
model is to be found in the good agreement between
dred times smaller than that for the other chain prop-
agation step (3). These analyses also show the relative
importance of the molecular step (1), the chain initi-
ation step (2), the transfer steps (5), (Ϫ5), (6), and
3
experimental and simulated concentrations of the
CClF"CH product (see Fig. 4) at a temperature
2
about 100 K higher than the highest temperature used
for the optimization of the model. The molecular
model prediction is not much lower (see also Fig. 4).
This could explain why Sianesi et al. [4] did not ob-
serve a large inhibitory effect of added NO.
(Ϫ6), and the termination steps (Ϫ2), (7), and (8), as
well as the low sensitivity to the rate constant of the
reverse steps (Ϫ1), (Ϫ3), and (Ϫ4), and of the added
It thus seems that the molecular pathway plays a
much more important role in the dehydrochlorination
of CCl FCH than that suggested in [4].
2
3
Pyrolysis of CCl FCH in the Presence of
2
3
Propene
The pyrolysis of CCl FCH has also been studied in
2
3
the presence of propene added as radical scavenger
between 650 and 700 K. The pressure of CCl FCH3
2
ranged from 15 to 120 torr and that of propene from
0
.5 to 7 torr. The addition of propene slightly reduces
2The model consisted of the reactions from Table I, the isom-
erization, the decomposition of the produced radicals, their reactions
with HCl and Cl , and all possible reverse reactions and chain ter-
Figure 3 Pyrolysis of 107.0 torr CCl FCH at 654.0 K (see
2
2
3
minations.
Fig. 2). Concentrations C of radicals and Cl atoms vs. re-
action time t. Simulations using optimized Arrhenius param-
eters from Table I.
3Calculated for experimental conditions from Sianesi et al. [4]
(
200 torr of CCl FCH at 803 K and a reaction time of 2 s) using
2 3
the rate constant measured by these authors.

1
96
HUYBRECHTS AND EERDEKENS
Figure 5 Pyrolysis of CCl FCH in the presence of pro-
Figure 7 Pyrolysis of 48.1 torr CCl FCH in the presence
2 3
2
3
pene. Concentration C of CClF"CH vs. reaction time t.
of 6.3 torr CCl at 655.5 K. Concentration C of CClF"CH2
2
4
(
•)—Temperature ϭ 650.8 K and initial pressures of
vs. reaction time t. (•)—Experimental; (Full curve)—Sim-
ulation using optimized Arrhenius parameters from Table I;
and (Dashed curve)—Simulation in the absence of added
CCl4.
CCl FCH and propene ϭ 58.2 and 1.6 torr, respectively;
2
3
(ꢂ)—Temperature ϭ 698.7 K and initial pressures of
CCl FCH and propene ϭ 52.5 and 1.82 torr, respectively;
2
3
and (Full curves)—Simulation using only the molecular re-
action (1) and its optimized Arrhenius parameters from Ta-
ble I.
A are 57.05 kcal/mol and 101 s , respectively (see
4.02
Ϫ1
4
Table I). These values fit the experimental data very
well (see Fig. 5). The value of E is to be compared
with the values of 56.0 and 58.5 kcal/mol obtained
from chemical activation experiments [21] and ab in-
itio quantum chemical calculations [22], respectively.
Note that the molecular elimination of HF has a 14
kcal/mol higher E [21]. This means that at a mean
temperature of 675 K the ratio of concentrations
the reaction rate and the autoacceleration disappears.
The amount of C H is of no influence. The reaction
3
6
observed must therefore correspond to the maximally
inhibited dehydrochlorination. It is of the first order.
Its rate can thus be attributed to the homogeneous mo-
lecular elimination of HCl. The optimized values for
the activation energy E and the preexponential factor
[CCl "CH ]/[CFCl"CH ] should be on the order
2 2 2
Ϫ
4
Ϫ1
of 10 . The much higher value observed (about 10 )
suggests heterogeneous rather than homogeneous HF
elimination in this work.
Pyrolysis of CCl FCH in the Presence of
2
3
CCl4
The pyrolysis of CCl FCH has also been studied in
2
3
the presence of added CCl at temperatures between
4
6
12 and 656 K. The pressure ranged from 36 to 104
torr for CCl FCH and from 2 to 8 torr for CCl . Fig-
2
3
4
ures 6 and 7 show that in the temperature range stud-
ied, the dehydrochlorination is much faster when CCl4
is added and that its rate also increases in the course
of time. As also can be seen, this autoacceleration is
well described by the optimization model. Analyses of
the rates of the elementary reaction steps show that (i)
Figure 6 Pyrolysis of 98.3 torr CCl FCH in the presence
2
3
of 8.0 torr CCl at 612.6 K. Concentration C of CClF"CH2
4
vs. reaction time t. (•)—Experimental; (Full curve)—Sim-
ulation using optimized Arrhenius parameters from Table I;
and (Dashed curve)—Simulation in the absence of added
CCl4.
4Optimizations based solely on the experiments in the presence
of propene yield almost the same Arrhenius parameters (see Table
I); this also holds when only the experiments with pure CCl FCH
2
3
are used.

PYROLYSIS OF 1,1-DICHLORO-1-FLUOROETHANE
197
the acceleration is due to the supplementary produc-
tion of Cl atoms by the fast chain initiation step (9),
and (ii) the autoacceleration results from reactions (11)
model also enables one to explain why Sianesi et al.
observed only a weak inhibitory effect of added NO
[4] and to determine the Arrhenius parameters of the
molecular dehydrochlorination even from experiments
in the absence of added propene.
and (12), which convert unreactive CCl D radicals into
3
reactive CCl FCH D and Cl chain carriers, respec-
2
2
tively. Figure 8 shows that the concentration of the
CCl D radicals remains almost constant in the course
3
of reaction, while the concentrations of the chain car-
riers increase. It also appears that the concentration of
the CCl FCH D radical is so low that its participation
BIBLIOGRAPHY
1. Huybrechts, G.; Hubin, Y.; Van Mele, B. Int J Chem
Kinet 1989, 21, 575.
2
2
in the chain terminations is negligible. This is also true
2
3
4
. Huybrechts, G.; Hubin, Y. Int J Chem Kinet 1985, 17,
57.
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968, 50, 619.
for the unreactive DCClFCH radical, except at the be-
3
1
ginning of the reaction.
For the sake of completeness, numerical calcula-
tions show that (i) the reactions (5), (6), (10), and (12)
tend rapidly towards a steady state of quasiequili-
3
1
brium; (ii) the amounts of the side products Cl2,
5. Huybrechts, G.; Van Assche, G.; Van der Auwera, S.
Int J Chem Kinet 1998, 30, 359.
6. Huybrechts, G.; Narmon, M.; Van Mele, B. Int J Chem
Kinet 1996, 28, 27.
CHClFCH , CCl H, and C Cl formed in steps (10) to
3
3
2
6
3
(
13), respectively, are at least 10 times lower than that
of the reaction product CClF"CH ; and (iii) CCl is
2
4
almost not consumed in the course of the reaction.
7. Huybrechts, G.; Theys, J.; Van Mele, B. Int J Chem
Kinet 1996, 28, 755.
8
. Huybrechts, G.; Van Assche, G. Comput Chem 1998,
2, 413.
2
CONCLUSION
9
. Huybrechts, G.; Hubin, Y.; Van Mele, B. Int J Chem
Kinet 1992, 24, 671.
2
The kinetics of the dehydrochlorination of CCl FCH3
10. Talhaoui, A.; Louis, F.; Devolder, P.; Meriaux, B.; Saw-
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erates and rapidly becomes equally fast. In the pres-
ence of CCl , on the other hand, the radical reaction
4
12. Martens, G. J.; Godfroid, M.; Delvaux, J.; Verbeyst, J.
is always much faster than the molecular reaction and
accelerates, too. All these observations can be quan-
titatively described by the model given in Table I. This
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2
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Figure 8 Pyrolysis of 48.1 torr CCl FCH in the presence
2
3
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4
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2
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