Kinetic and product study of the Cl-initiated oxidation of 1,2,3-trichloropropane (CH2ClCHClCH2Cl)

Article abstract of DOI:10.1021/jp002227m

The kinetics and products of the Cl atom initiated oxidation of 1,2,3-trichloropropane were studied using FTIR-smog chamber systems at (295 ± 2) K in 700-760 torr of air. The major oxidation product in terms of carbon balance was 1,3-dichloroacetone with smaller amounts of HC(O)Cl and CH₂ClC(O)Cl. Chemical activation effects played a significant role in the atmospheric fate of CH₂ClCHClO(·) and CH₂ClCO(·)ClCH₂Cl radicals. The UV-visible spectrum of CH₂ClC(O)CH₂Cl was measured at 270-385 nm and has a maximum at 305 nm where σ = (1.6 ± 0.2) × 10^-19 sq cm/molecule (base e). Assuming a photolysis quantum yield of 1-0.04, the lifetime of CH₂ClC(O)CH₂Cl with respect to photolysis on a summer day of 40° latitude was 0.5-12 hr. Photolysis was likely to be the dominant atmospheric loss mechanism of CH₂ClC(O)CH₂Cl. The results were discussed in the context of the atmospheric chemistry of 1,2,3-trichloropropane.

Full text of DOI:10.1021/jp002227m

J. Phys. Chem. A 2001, 105, 5123-5130
5123
Kinetic and Product Study of the Cl-Initiated Oxidation of 1,2,3-Trichloropropane
(CH2ClCHClCH2Cl)
I. Voicu, I. Barnes,* and K. H. Becker
Bergische UniVersita¨t GH Wuppertal/ FB 9 Physikalische Chemie,
Gaussstrasse 20, D-42097 Wuppertal, Germany
T. J. Wallington*
Ford Research Laboratory, SRL-3083, Ford Motor Company, P.O. Box 2053, Dearborn, Michigan 48121-2053
Y. Inoue and M. Kawasaki†
Department of Molecular Engineering, Kyoto UniVersity, Kyoto 606-8501, Japan
ReceiVed: June 21, 2000; In Final Form: March 19, 2001
The kinetics and products of the Cl atom initiated oxidation of CH2ClCHClCH2Cl (1,2,3-trichloropropane)
have been investigated at (295 ( 2) K in 700-760 Torr of air in a 405 L reaction chamber. The major
oxidation product (in terms of carbon balance) was CH2ClC(O)CH2Cl with smaller amounts of HC(O)Cl and
CH2ClC(O)Cl. It was observed that chemical activation effects play a significant role in the atmospheric fate
of CH2ClCHClO(‚) and CH2ClCO(‚)ClCH2Cl radicals. Relative rate techniques were used to measure the
following: k(Cl + CH2ClCHClCH2Cl) ) (1.86 ( 0.32) × 10-12, k(Cl + CHCldCHCH2Cl) ) (1.67 ( 0.18)
× 10-10, k(Cl + CH2dCClCH2Cl) ) (1.46 ( 0.15) × 10-10, and k(Cl + CH2ClC(O)CH2Cl) ) (5.53 ( 0.63)
× 10-13 cm3 molecule-1 s-1. The UV-visible spectrum of CH2ClC(O)CH2Cl was measured over the range
270-385 nm and has a maximum at 305 nm where σ ) (1.6 ( 0.2) × 10-19 cm2 molecule-1 (base e).
Assuming a photolysis quantum yield of 1.00-0.04, the lifetime of CH2ClC(O)CH2Cl with respect to photolysis
on a summer day at 40° latitude is calculated to be 0.5-12 h. Photolysis is likely to be the dominant atmospheric
loss mechanism of CH2ClC(O)CH2Cl. The results are discussed in the context of the atmospheric chemistry
of 1,2,3-trichloropropane.
1. Introduction
radicals derived from CH3Cl and C2H5Cl; three-center intramo-
lecular elimination of HCl.4-8 However, it is unclear as to
1,2,3-Trichloropropane is a volatile (bp 156 °C) chlorinated
solvent used in paint removal and degreasing operations.
Assessment of the environmental impact of organic compounds
such as trichloropropane released into the atmosphere requires
a detailed understanding of their atmospheric degradation
pathways. Little is currently known about the atmospheric
oxidation mechanism of trichloropropane.
Alkoxy radicals are important intermediates in the atmo-
spheric oxidation of all organic compounds. At the present time
there are significant uncertainties in our understanding of the
atmospheric chemistry of alkoxy radicals. Reaction of alkyl
peroxy radicals with NO can produce alkoxy radicals possessing
internal excitation that is comparable to, or greater than, the
barrier to decomposition. These “hot” alkoxy radicals (e.g., CF3-
CFHO(‚),1 CH2ClO(‚),2 and HOC2H4O(‚)3) can decompose
immediately and play an important role in dictating the nature
of the atmospheric oxidation products. Alkoxy radicals formed
in the oxidation of compounds such as trichloropropane possess
a variety of potentially accessible decomposition pathways
(elimination of Cl atoms, HCl) and may be prone to chemical
activation effects not recognized previously.
whether three-center intramolecular elimination of HCl is of
general importance in the atmospheric oxidation of chlorinated
organic compounds. To improve the technical basis for predic-
tions of the environmental impact of industrial solvents we have
conducted a study of the atmospheric chemistry of 1,2,3-
trichloropropane.
The atmospheric oxidation of CH2ClCHClCH2Cl is initiated
by reaction with OH radicals producing alkyl radicals that will,
in turn, react with O2 to give peroxy radicals:
CH2Cl-CHCl-CH2Cl + OH f
CH2Cl-CHCl-C(‚)HCl + H2O (1a)
CH2Cl-CHCl-CH2Cl + OH f
CH2Cl-C(‚)Cl-CH2Cl + H2O (1b)
CH2Cl-CHCl-C(‚)HCl + O2 + M f
CH2Cl-CHCl-CHClO2(‚) + M (2a)
Experimental studies have demonstrated the importance of a
novel decomposition pathway for the R-monochloroalkoxy
CH2Cl-C(‚)Cl-CH2Cl + O2 + M f
CH2Cl-CClO2(‚)-CH2Cl + M (2b)
* To whom correspondence should be addressed. E-mail: barnes@
physchem.uni-wuppertal.de (I. Barnes) and E-mail: twalling@ford.com
(Wallington).
In urban air masses, the peroxy radicals will react with NO to
generate the alkoxy radicals CH2Cl-CHCl-CHClO(‚) and CH2-
† E-mail: mkawasa7@ip.media.kyoto-u.ac.jp.
10.1021/jp002227m CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/04/2001

5124 J. Phys. Chem. A, Vol. 105, No. 21, 2001
Voicu et al.
Cl-CClO(‚)-CH2Cl which will react further to give a diverse
array of halogenated products.
spectral range of 70 nm on the diode array detector. The
wavelength scale was calibrated using atomic emission lines
from a low-pressure mercury lamp. The UV absorbance
increased linearly with CH2ClC(O)CH2Cl concentration in
accordance with Lambert-Beer’s law, ln(Io/I) ) σcl. The
products of the Cl atom initiated oxidation of trichloropropane
in the present and absence of NOx were investigated at Ford
using a 140 L Pyrex reactor10 surrounded by 22 fluorescent
blacklamps (GTE F40BLB, λ > 300 nm). All experiments were
performed at 700-760 Torr total pressure (N2 + O2) and 296
( 3 K.
In the initial stages of this work a relative kinetic and product
study of the reaction of CH2ClCHClCH2Cl with OH radicals
was attempted; however, with the source of OH radicals
employed (the photolysis of methyl nitrite) the reaction was
too slow to produce accurate results. Thus, in the present work,
reaction with Cl was substituted for reaction with OH. Although
reaction of volatile organic compounds (VOCs) with Cl atoms
is, in general, not as selective as with OH radicals the subsequent
chemistry is the same and thus it is a convenient method to
emulate OH radical initiated chemistry.
3. Results and Discussion
We present here the results of a kinetic and mechanistic study
of the Cl atom initiated oxidation of CH2ClCHClCH2Cl using
FTIR-smog chamber systems at the Bergische Universita¨t GH
Wuppertal and Ford Motor Company.
3.1. Relative Rate Kinetic Studies of Cl Atoms with
Halogenated Organics. Prior to investigating the oxidation
products of 1,2,3-trichloropropane, relative rate experiments
were performed to study the kinetics of reactions of Cl with
1,2,3-trichloropropane (CH2ClCHClCH2Cl), 1,3-dichloropro-
pene (CHCldCHCH2Cl), 2,3-dichloropropene (CH2dCClCH2-
Cl), and 1,3-dichloroacetone (CH2ClC(O)CH2Cl). Reaction 3
was measured relative to (9) and (10), reactions 6 and 7 were
measured relative to (11) and (12), and reaction 8 was studied
relative to (9, 13, and 14).
Cl + CH2ClCHClCH2Cl f products
2. Experimental Section
(3)
The majority of experiments were performed at Wuppertal
using a 405 L Pyrex cylindrical glass reactor (1.5 m length, 0.6
m diameter) with Teflon coated metal end flanges described
elsewhere.9 A White mirror system (base path length 1.4 m)
mounted inside the reactor and coupled by an external mirror
system to a Fourier Transform-Spectrometer (Nicolet 7199)
enables the in-situ monitoring of both reactants and products
by long path infrared absorption, using a total path length 50.4
m. The reactor is equipped with 18 fluorescent lamps (Philips
TLA 40 W/ 05: 320 < λ < 480 nm, λmax ) 365 nm) arranged
concentrically around the chamber. Experiments were performed
in 700-760 Torr total pressure of synthetic air at 295 ( 2 K.
Rate constants for reactions of Cl atoms with trichloropro-
pane, 1,3-dichloropropene, 2,3-dichloropropene, and 1,3-dichlo-
roacetone were determined at Wuppertal using the relative rate
method in which the reactant and reference are exposed to attack
by Cl atoms.
Cl + CH2ClCHClCH2Cl f products
Cl + CHCldCHCH2Cl f products
Cl + CH2dCClCH2Cl f products
Cl + CH2ClC(O)CH2Cl f products
Cl + CH3OCHO f products
Cl + CH3CH2Cl f products
Cl + C2H6 f products
(3)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
Cl + C3H6 f products
Cl + reactant organic f products
(4)
(5)
Cl + reference compound f products
Cl + CH3Cl f products
Provided that the reactant and reference compounds are removed
solely by reaction with Cl atoms and are not formed in any
process, then it can be shown that
Cl + CH4 f products
Figures 1 and 2 show plots of the loss of reactants versus
reference compounds following exposure to Cl atoms in 700-
760 Torr of air. Rate constant ratios, kcompd/kref, derived from
linear least-squares analysis of the data in Figures 1 and 2 are
given in Table 1. Quoted errors for kcompd/kref in Table 1 are
two standard deviations from the least squares analyses. The
[reactant]t0
[reactant]t
k
[reference]t0
[reference]t
ln
)
4 ln
(i)
(
)
(
)
k5
Plots of ln([reactant]t0/[reactant]t) versus ln([reference]t0/[ref-
erence]t) yield slopes of k4/k5.
relative rate data can be placed upon an absolute basis using k9
-11 13
Reactants were injected into the reactor in a stream of
synthetic air or nitrogen using microliter syringes for liquids
and gastight syringes for gases. Concentrations of the organic
reactants were in the range (19-26) ppm (1 ppm ) 2.48 ×
1013 molecule cm-3 at 298 K). The photolysis of Cl2 (70-100
ppm) was used to generate Cl atoms. The Cl atom concentrations
) 1.4 × 10-12 11
,
k10 ) 8.04 × 10-12 12
,
k11 ) 5.7 × 10
,
k12 ) 2.48 × 10-10 14
,
k13 ) 4.9 × 10-13 15
and k14 ) 1.0 ×
,
10-13 cm3 molecule-1 s-1 14
As seen in Table 1, consistent
.
values of kcompd were obtained using multiple reference com-
pounds suggesting the absence of substantial systematic errors
associated with the use of individual reference reactions. We
chose to quote final values of k3, k6, k7, and k8 which are
averages of the individual measurements, together with error
limits which encompass the extremes of the individual deter-
minations. Hence, k3 ) (1.86 ( 0.32) × 10-12, k6 ) (1.67 (
0.18) × 10-10, k7 ) (1.46 ( 0.15) × 10-10, k8 ) (5.53 ( 0.63)
× 10-13 cm3 molecule-1 s-1. We estimate that potential
systematic errors associated with uncertainties in the reference
rate constants contribute an additional 10% to the uncertainty
were typically (4-9) × 109 cm-3
.
The UV-absorption spectrum of CH2ClC(O)CH2Cl was
measured in a 480 L volume reactor at Wuppertal equipped
with multiple reflection mirror optics for simultaneous in situ
measurement in the UV and IR. The UV spectrometer consists
of a modified 22-cm monochromator (SPEX) and a diode array
detector (EG & G PAR 1412). A spectral resolution of 0.6 nm
was achieved with a grating of 1200 lines/mm covering a

Cl-Initiated Oxidation of 1,2,3-Trichloropropane
J. Phys. Chem. A, Vol. 105, No. 21, 2001 5125
TABLE 1: Kinetic Data for Cl Atom Reactions Investigated in This Study
rate coefficient ratio
rate coefficient kcompd
(cm3 molecule-1 s-1
recommended value kcompd
(cm3 molecule-1 s-1
compound (compd)
reference (ref)
kcompd/ kref
)
)
CH2ClCHClCH2Cl
(1,2,3-trichloropropane)
CH2Cl-CHdCHCl
(1,3-dichloropropene)
CH2Cl-CCldCH2
(2,3-dichloropropene)
CH2ClC(O)CH2Cl
CH3OCHO
C2H5Cl
CH3CH3
CH3CHdCH2
CH3CH3
CH3CHdCH2
CH4
1.22 ( 0.12
0.25 ( 0.02
3.06 ( 0.20
0.65 ( 0.04
2.41 ( 0.07
0.63 ( 0.01
5.7 ( 0.5
(1.71 ( 0.17) × 10-12
(2.01 ( 0.16) × 10-12
(1.74 ( 0.11) × 10-10
(1.61 ( 0.10) × 10-10
(1.36 ( 0.05) × 10-10
(1.57 ( 0.02) × 10-10
(5.7 ( 0.5) × 10-13
(5.0 ( 0.4) × 10-13
(5.9 ( 0.7) × 10-13
(1.86 ( 0.32) × 10-12
(1.67 ( 0.18) × 10-10
(1.46 ( 0.15) × 10-10
(5.53 ( 0.63) × 10-13
(1,3-dichloroacetone)
CH3Cl
CH3OCHO
1.04 ( 0.08
0.42 ( 0.05
CHCl2CHClCH2Cl
(1,1,2,3-tetrachloropropane)
CH2ClCCl2CH2Cl
(9.3 ( 2.0) × 10-13
(1.7 ( 1.0) × 10-13
(1,2,2,3-tetrachloropropane)
range. There are no previous studies of these reactions with
which to compare our results.
3.2. Reaction Site Selectivity for Cl + 1,2,3-Trichloropro-
pane. To ascertain the relative importance of Cl atom attack at
the terminal and central H atoms in 1,2,3-trichloropropane,
experiments were performed in which mixtures of CH2-
ClCHClCH2Cl and Cl2 in 760 Torr of N2 diluent were subjected
to UV irradiation. The alkyl radicals formed following H atom
abstraction react with Cl2 to give either 1,1,2,3-tetrachloropro-
pane (terminal H abstraction) or 1,2,2,3-tetrachloropropane
(central H abstraction)
CH2Cl-CHCl-CH2Cl + Cl f
CH2Cl-CHCl-C(‚)HCl + HCl (3a)
CH2Cl-CHCl-CH2Cl + Cl f
CH2Cl-C(‚)Cl-CH2Cl + HCl (3b)
CH2Cl-CHCl-C(‚)HCl + Cl2 f
CH2Cl-CHCl-CHCl2 + Cl (15a)
CH2Cl-C(‚)Cl-CH2Cl+ Cl2 f
CH2Cl-CCl2-CH2Cl + Cl (15b)
The yields of 1,1,2,3- and 1,2,2,3-tetrachloropropane provide
information on the importance of Cl attack at the central and
terminal H atoms, respectively. Unfortunately, neither of the
tetrachloropropanes are commercially available. To obtain
calibrated infrared spectra of these compounds they were
produced in-situ from 1,3-dichloropropene and 2,3-dichloro-
propene (which are commercially available) by UV irradiation
of dichloropropene/Cl2 mixtures in 760 Torr of N2. By analogy
to the reaction with propene,16 it is reasonable to assume that
the reaction of Cl atoms with dichloropropene proceeds
predominately via addition to the double bond and that the fate
of the resulting chloroalkyl radical is reaction with Cl2.
Figure 1. Loss of trichloropropane (A) and 1,3-dichloropropene (B)
versus reference compounds following exposure to Cl atoms in 760
Torr of air at 296 K.
CH2Cl-CHdCHCl
(1,3-dichloropropene)
+ Cl2 + hv f f
The filled symbols in Figure 3 show the observed formation
of 1,1,2,3- and 1,2,2,3-tetrachloropropane versus consumption
of 1,2,3-trichloropropane following UV irradiation of trichloro-
propane/Cl2/N2 mixtures. The dotted lines are second-order fits
to the data to aid visual inspection of the data trends. We
attribute the curvature of the plot to secondary loss of tetra-
chloropropane via reaction with Cl atoms. Control experiments
in which reaction mixtures were allowed to stand in the chamber
in the dark revealed no evidence for heterogeneous loss of
tetrachloro- or trichloropropanes. To derive values for the yields
of the tetrachloropropanes and their reactivity with Cl atoms
CH2Cl-CHCl-CHCl2
(1,1,2,3-tetrachloropropane)
(16)
CH2Cl-CCldCH2
(2,3-dichloropropene)
+ Cl2 + hv f f
CH2Cl-CCl2-CH2Cl
(1,2,2,3-tetrachloropropane)
(17)
Calibration of the spectra was achieved by assuming 100%
conversion of dichloropropene into tetrachloropropane.

5126 J. Phys. Chem. A, Vol. 105, No. 21, 2001
Voicu et al.
( 0.32) × 10-12 cm3 molecule-1 s-1 (see section 3.1) results
in the values for k18 given in Table 1.
Combining the branching ratios above with k3 ) (1.86 (
0.32) × 10-12 gives k3a ) (7.3 ( 1.5) × 10-13 and k3b ) (1.1
( 0.2) × 10-12 cm3 molecule-1 s-1. The reactivity of each
-CH2Cl group in trichloropropane is k3a/2 ) (3.6 ( 0.7) ×
10-13 cm3 molecule-1 s-1. As might be expected from such
structurally similar molecules, this result is comparable to the
reactivity of a -CH2Cl group in CH2ClCH2Cl: (6.5 ( 1.0) ×
10-13 cm3 molecule-1 s-1 18
.
3.3. Is Chemical Activation Important for CH2ClCHClO-
(‚) Radicals? Prior to the investigation of the Cl-initiated
oxidation of 1,2,3-trichloropropane a limited set of experiments
were conducted to determine if chemical activation is an
important factor in the fate of CH2ClCHClO(‚) radicals.
Experiments were first conducted using a mixture containing
26 mTorr of CH2ClCH2Cl and 160 mTorr of Cl2 in 700 Torr of
air. UV irradiation led to the formation of HC(O)Cl and CH2-
ClC(O)Cl in molar yields of 53 ( 6% and 15 ( 2%,
respectively. These results are in excellent agreement with yields
of 56 ( 4% and 16 ( 2% for these species reported previously.18
Experiments were then performed in the presence of NO using
mixtures containing 26 mTorr of CH2ClCH2Cl, 160 mTorr of
Cl2, 30 mTorr of NO, and either 126 or 401 Torr of O2 in 700
Torr total pressure with N2 diluent. HC(O)Cl was observed in
a yield comparable to that observed in the absence of NO.
Interestingly, in the presence of NO there was no observable
formation of CH2ClC(O)Cl (<3% yield).
Reaction of Cl atoms with 1,2-dichloroethane gives CH2ClC-
(‚)HCl radicals which add O2 to give peroxy radicals, CH2-
ClCHClO2(‚), which are then converted into alkoxy radicals,
CH2ClCHClO(‚), either via self-reaction or, when NO is present,
via reaction with NO.
Figure 2. Loss of 2,3-dichloropropene (A) and dichloroacetone (B)
versus reference compounds following exposure to Cl atoms in 760
Torr of air at 296 K.
CH2ClC(‚)HCl + O2 + M f CH2ClCHClO2(‚) + M (19)
the following expression17 was fit to the data in Figure 3
CH2ClCHClO2(‚) + CH2ClCHClO2(‚) f
[tetrachloropropane]t
CH2ClCHClO(‚) + CH2ClCHClO(‚) + O2 (20a)
)
[1,2,3-trichloropropane]t0
CH2ClCHClO2(‚) + CH2ClCHClO2(‚) f
R
(1 - x)[(1 - x){k18/k3} - 1] (I)
CH2ClC(O)Cl + CH2ClCHClOH + O2 (20b)
k18
1 -
k3
CH2ClCHClO2(‚) + NO f CH2ClCHClO(‚) + NO2 (21)
where x is the conversion of 1,2,3-trichloropropane, defined as
CH2ClCHClO(‚) radicals formed in reaction 20a undergo
[1,2,3-trichloropropane]t
reaction with O2 and intramolecular HCl elimination.18
x ≡ 1 -
[1,2,3]trichloropropanet
0
CH2ClCHClO(‚) + M f CH2ClC(‚)O + HCl + M (22)
CH2ClCHClO(‚) + O2 f CH2ClC(O)Cl + HO2 (23)
R is the molar yield of the tetrachloropropane, and k3 and k18
are the rate constants for reactions 3 and 18.
Using experiments employing reaction 20a as a source of CH2-
tetrachloropropane + Cl f products
(18)
ClCHClO(‚), it has been reported that k23/k22 ) 2.3 × 10-20
A fit of expression I to the data in Figure 3 gives R ) 0.70
( 0.09 and 0.44 ( 0.05 and k18/k3 ) 0.09 ( 0.05 and 0.50 (
0.06 for 1,2,2,3- and 1,1,2,3-tetrachloropropane, respectively.
Corrections to account for loss of the tetrachloropropanes can
be calculated using the values of k18/k3 derived above to give
the data indicated by the open symbols in Figure 3. Normalizing
the combined product yield to 100% gives k3a/(k3a+k3b) ) 0.39
( 0.04 and k3b/(k3a+k3b) ) 0.61 ( 0.08. Quoted errors include
our estimate of uncertainties associated with the tetrachloro-
propane calibrations and corrections for their reaction with Cl.
Combination of the k18/k3 rate constant ratios with k3 ) (1.86
cm3 molecule-1 18
. Hence, in the presence of 401 Torr O2 the
yield of CH2ClC(O)Cl is expected to be 22%. The absence of
CH2ClC(O)Cl can be explained by the fact that reaction 21 is
more exothermic than reaction 20a. Reaction 21 may produce
CH2ClCHClO(‚) radicals possessing significant internal excita-
tion which undergo decomposition on a time scale too short
for the bimolecular reaction 23 to compete. It appears that
chemical activation plays a significant role in the atmospheric
chemistry of CH2ClCHClO(‚) radicals.
3.4. Product Study of Cl-Initiated Oxidation of 1,2,3-
Trichloropropane with/without NO Present. The products of

Cl-Initiated Oxidation of 1,2,3-Trichloropropane
J. Phys. Chem. A, Vol. 105, No. 21, 2001 5127
Figure 5. Formation of CH2ClC(O)CH2Cl (squares), HC(O)Cl (circles),
and CH2ClC(O)Cl (triangles) versus loss of trichloropropane following
the Cl atom initiated oxidation of trichloropropane in the presence of
NOx. Experiments were conducted in 700 Torr total pressure of N2 at
296 K with [O2] ) 17 (open), 147 (gray), or 554 Torr (filled symbols).
Figure 3. Formation of 1,2,2,3- and 1,1,2,3-tetrachloropropane versus
loss of trichloropropane following UV irradiation of trichloropropane/
Cl2/N2 mixtures. Filled symbols are observed data; open symbols have
been corrected for secondary reaction with Cl atoms.
Comparison of panel B with reference spectra of HC(O)Cl, CH2-
ClC(O)CH2Cl, and CH2ClC(O)Cl in panels C-E shows these
species are products. In the Cl atom initiated oxidation of CH2-
ClCHClCH2Cl, three carbon-containing products were readily
identified: HC(O)Cl, CH2ClC(O)Cl, and CH2ClC(O)CH2Cl. In
addition, a small unidentified product feature was observed at
1802 cm-1. The unknown increased with increasing [O2] and
was not present in experiments conducted in the presence of
NO. We tentatively assign the unknown to CH2ClCHClC(O)-
Cl. Features attributable to CO and CO2 were observed. The
molar CO2 yield was approximately 40%. The molar CO yield
was inversely dependent on the O2 partial pressure and varied
from ≈10% in experiments conducted in 700 Torr of O2 in the
absence of NO to ≈55% in experiments with an O2 partial
pressure of 16 Torr in the presence of NO. Figure 5 shows the
formation of HC(O)Cl, CH2ClC(O)Cl, and CH2ClC(O)CH2Cl
versus loss of trichloropropane following irradiation of tri-
chloropropane/Cl2/NO/O2/N2 mixtures. Small corrections (<10%)
were applied to the HC(O)Cl and CH2ClC(O)CH2Cl data to
account for loss of these species via reaction with Cl atoms.
Corrections were computed using the kinetic data reported in
section 3.1 and k(Cl+HC(O)Cl) ) 7.8 × 10-13 cm3 molecule-1
s-19 using the expression17
correction factor )
x
1
kprod
(1 - x)[(1 - x){kprod/k3 - 1} - 1]
Figure 4. Spectra acquired before (A) and after (B) a 470 s irradiation
of a mixture containing 20 ppm CH2ClCHClCH2Cl and 73 ppm Cl2 in
760 Torr of synthetic air. Reference spectra of HC(O)Cl (C), CH2ClC-
(O)Cl (D), and CH2ClC(O)CH2Cl (E) are shown for comparison.
)
1 -
[
(
)
k3
The “correction factor” is the factor by which the observed
product yield needs to be mulitiplied to account for secondary
loss via reaction with Cl atoms, “x” is the fractional consumption
of trichloropropane, and k3 and kprod are the bimolecular rate
constants for reaction of Cl atoms with trichloropropane and
the product. To facilitate accurate corrections for secondary
reactions a product study of the Cl atom initiated oxidation of
dichloroacetone in air was performed. UV irradiation of
dichloroacetone/Cl2/air mixtures produced HC(O)Cl in a molar
yield indistinguishable from 200%. This finding is consistent
the Cl atom initiated oxidation of trichloropropane in 700 Torr
of synthetic air were studied using the UV irradiation of mixtures
of 15-30 mTorr trichloropropane, 50-200 mTorr Cl2, 0-30
mTorr NO, and either 16-700 Torr of O2 in 700 Torr total
pressure using N2 diluent. Figure 4 shows typical infrared spectra
in the wavenumber region (2200-1700) cm-1 obtained before
(A) and after (B) UV irradiation of a mixture of 15 mTorr CH2-
ClCHClCH2Cl and 50 mTorr Cl2 in 700 Torr of synthetic air.

5128 J. Phys. Chem. A, Vol. 105, No. 21, 2001
Voicu et al.
TABLE 2: Product Data for the Cl Atom Initiated
Oxidation of 1,2,3-Trichloropropane in 700 Torr of N2/O2
Diluent at 298 K
molar yield (%)
(without NOx)
molar yield (%)
[O2] ) [O2] ) [O2] )
(with NOx)
product
HC(O)Cl
CH2ClC(O)Cl
16 Torr 147 Torr 700 Torr [O2] ) 16-554 Torr
55 ( 4 57 ( 5 47 ( 5
13 ( 1 13 ( 1 18 ( 2
68 ( 7
24 ( 3
39 ( 5
78 ( 9
CH2ClC(O)CH2Cl 36 ( 3 36 ( 3 35 ( 3
carbon balance
63 ( 5 64 ( 6 63 ( 6
with the atmospheric oxidation mechanism of acetone20 and
butadione.21 Reaction of Cl atoms with CH2ClC(O)Cl is 1.9 ×
10-12/6.4 × 10-14 18 ) 30 times slower than with trichloropro-
pane; no correction of the CH2ClC(O)Cl data is required. As
seen from Figure 5, there was no discernible effect of [O2] on
the product yields observed in the presence of NO. Linear least-
squares analysis of the data in Figure 5 gives molar yields (%)
for HC(O)Cl, CH2ClC(O)Cl, and CH2ClC(O)CH2Cl of 68 (
7, 24 ( 3, and 39 ( 5 for the Cl atom initiated oxidation of
1,2,3-trichloropropane in the presence of NO. Results obtained
in the presence and absence of NOx are given in Table 2. As
shown in Table 2, there was a small but significant effect of
[O2] on the yields of HC(O)Cl and CH2ClC(O)Cl observed in
experiments in the absence of NO. The increased CH2ClC(O)-
Cl and decreased HC(O)Cl yields observed in the experiment
conducted in 700 Torr of O2 presumably reflect the competition
of reactions 22 and 23 for the available CH2ClCHClO(‚)
radicals.
At this point it is germane to consider possible additional
losses of these products in the chamber. None of the products
are expected to be photolyzed significantly by the UV black-
lamps for the 10-60 s irradiation periods used in this work.
To check for possible heterogeneous losses, reaction mixtures
were allowed to stand in the dark; there were no significant
losses (<2%) of any of these compounds over the time scale
of the experiments.
3.5. UV-Visible Absorption Spectrum of CH2ClC(O)-
CH2Cl. Eight separate injections of CH2ClC(O)CH2Cl were
made into the 480-L chamber in Wuppertal of 4-25 ppm of
CH2ClC(O)CH2Cl. The resulting UV and IR spectra scaled
linearly (to within (5%) with the CH2ClC(O)CH2Cl concentra-
tion. The UV spectrum had a maximum at 305 nm. Values of
σ (305 nm) ) (1.6 ( 0.2) × 10-19 cm2 molecule-1 and σ (1750
cm-1) ) 5.8 × 10-19 cm2 molecule-1 (both base e) were
obtained. The quoted errors reflect uncertainties associated with
the reproducibility of the measurements and our estimate of
possible systematic errors associated with uncertainties in the
UV and IR path length, calibration of the CH2ClC(O)CH2Cl
concentration, and sample purity. Figure 6 shows the UV-
visible absorption spectrum of CH2ClC(O)CH2Cl measured in
the present work together with spectra of acetone (average from
refs 22 and 23) and chloroacetone.24 As seen from Figure 6,
chlorination of acetone results in a red shift and increase of the
UV absorption spectrum. Prolonged exposure of CH2ClC(O)-
CH2Cl/air mixtures in the reaction chamber to UV irradiation
led to the formation of two products: HC(O)Cl and CO2.
Formation of these products suggests that photolysis proceeds
to give CH2ClC(O) and CH2Cl radicals which add O2 to give
the corresponding peroxy radicals which are then converted into
HC(O)Cl.2
Figure 6. UV spectra of CH2ClC(O)CH2Cl (this work), CH3C(O)CH2-
Cl,24 and CH3C(O)CH3.22
are required:
j ) σ(λ)φ(λ)I(λ)dλ
∫
λ
While no gas-phase photolysis quantum yield data are available
for CH2ClC(O)CH2Cl (to the best of our knowledge) such data
are available for acetone. At the maximum of the UV absorption
(278 nm) the photodissociation quantum yield for acetone is
close to unity, at 300 nm the quantum yield is approximately
0.2, and at 330 nm the quantum yield drops to approximately
0.04.25 For simplicity we will assume that the quantum yield at
all wavelengths for CH2ClC(O)CH2Cl photolysis is less than
unity and greater than 0.04. Using actinic flux data from
Finlayson-Pitts and Pitts,26 the photolysis rate of CH2ClC(O)-
CH2Cl is calculated to lie in the range (0.2-5.6) × 10-4 s-1
for a solar zenith angle of 25 degrees (representative of a typical
summer day at 40°N), corresponding to a photolysis lifetime
of between 30 min and 12 h.
We can compare this result with the expected atmospheric
lifetime of CH2ClC(O)CH2Cl with respect to reaction with OH
radicals. Using k(OH+CH2ClC(O)CH2Cl) ) 5 × 10-13 27
,
an
atmospheric lifetime for methane of 9 years,28 and k(OH+CH4)
) 6.3 × 10-15 cm3 molecule-1 s-1 gives an atmospheric lifetime
of CH2ClC(O)CH2Cl with respect to reaction with OH radicals
of 40 days. We conclude that photolysis is the atmospheric fate
of CH2ClC(O)CH2Cl.
4. Discussion
4.1. Atmospheric Oxidation Mechanism of 1,2,3-Trichlo-
ropropane. The data in Table 2 provide insight into the
atmospheric oxidation mechanism of 1,2,3-trichloropropane. As
discussed above, the reaction of Cl atoms with 1,2,3-trichloro-
propane gives two different alkyl radicals which are expected
to rapidly (within 1 µs in an atmosphere of air) add O2 to give
alkyl peroxy radicals. Alkyl peroxy radicals (RO2) react rapidly
with NO via two pathways giving alkoxy radicals (RO) as major
products and organic nitrates (RONO2) as minor products.
RO2 + NO f RO + NO2
(24a)
(24b)
To determine a first-order photolysis rate (j) for CH2ClC-
(O)CH2Cl in the atmosphere, wavelength-dependent cross
section, σ(λ), quantum yield, φ(λ), and actinic flux, I(λ), data
RO2 + NO + M f RONO2 + M

Cl-Initiated Oxidation of 1,2,3-Trichloropropane
J. Phys. Chem. A, Vol. 105, No. 21, 2001 5129
The database concerning nitrate yields for reactions of alkyl
peroxy radicals with NO shows that the organic nitrate yield,
k19b/(k19a+k19b), increases with the size of the peroxy radical
from <0.005 for methylperoxy,29 0.036 for 1- and 2-propyl-
peroxy radicals,30 to 0.20-0.30 for heptyl- and octylperoxy
radicals.30 Organic nitrates have a characteristic IR feature at
1660-1670 cm-1 (asymmetric NO2 stretch).31 The product
spectra in the present work were examined for features which
could be assigned to organic nitrates; none were found. Using
an integrated absorption cross section of (2.5 ( 0.2) × 10-17
cm molecule-1 (base 10) for the asymmetric NO2 stretch31 an
upperlimit of 10% for the sum of the yields of CH2-
ClCHClCHClONO2 and CH2ClCCl(ONO2)CH2Cl was estab-
lished. The chlorinated peroxy radicals generated from trichlo-
ropropane generate far less organic nitrate than unsubstituted
alkyl peroxy radicals of comparable molecular weight. Hydroxy-32
and fluoro-33 substituted peroxy radicals also give lower nitrate
yields in their reactions with NO than comparable alkyl peroxy
radicals. At the present time the factors which dictate the nitrate
yield in reactions of peroxy radicals with NO are unclear.
However, in light of the similar effect of -OH, -F, and -Cl
substituents it seems reasonable to speculate that electron
withdrawing groups decrease the nitrate yield in reactions of
peroxy radicals with NO. In the following discussion we will
not consider nitrate formation further.
As seen from Table 2 the combined yield of dichloroacetone
and CH2ClC(O)Cl in the absence of NOx is smaller than that in
the presence of NOx, and the relative importance of the two
different products is different. By analogy to other peroxy radical
reactions,14 reaction 26 is expected to be 14 kcal mol-1 more
exothermic than reaction 29. Alkoxy radicals formed in reaction
26 may possess significant internal excitation. It appears that
chemical excitation of CH2ClCO(‚)ClCH2Cl radicals produced
in reaction 26 results in a greater fraction of these radicals
undergoing decomposition via C-C bond scission. As discussed
in the Introduction, such chemical activation effects have been
reported for several atmospherically relevant alkoxy radicals.
Let us now consider the fate of the alkoxy radical formed
following H-atom abstraction from the end of the trichloropro-
pane molecule. The CH2ClCHClCHClO(‚) radical can either
react with O2, decompose via intramolecular HCl elimination,
undergo C-C bond scission, or elimate a Cl atom.
CH2ClCHClCHClO(‚) + O2 f CH2ClCHClC(O)Cl + HO2
(30)
CH2ClCHClCHClO(‚) + M f
CH2ClCHClC(‚)(O) + HCl + M (31)
CH2ClCHClCHClO(‚) + M f
As stated in the Introduction a major goal of the present study
was to investigate the atmospheric fate of the two different
alkoxy radicals formed from 1,2,3-trichloropropane. To this end
it is useful to consider first the product data obtained from the
Cl-initiated oxidation in the presence of NO. In such experiments
the peroxy radicals derived from trichloropropane react with
NO to give two alkoxy radicals:
CH2ClC(‚)HCl + HC(O)Cl + M (32)
CH2ClCHClCHClO(‚) + M f
CH2ClCHClC(O)H + Cl + M (22)
The observation of a substantial HC(O)Cl yield shows that
reaction 30 does not dominate the fate of CH2ClCHClCHClO-
(‚) radicals. The CH2ClCHClC(‚)(O) radicals formed in reaction
31 will be converted into CH2ClC(‚)HCl radicals via
CH2ClCHClCHClO2(‚) + NO f
CH2ClCHClCHClO(‚) + NO2 (25)
CH2ClCHClC(‚)(O) + O2 + M f
CH2ClCHClC(O)O2(‚) + M (34)
CH2ClCO2(‚)ClCH2Cl + NO f
CH2ClCO(‚)ClCH2Cl + NO2 (26)
CH2ClCHClC(O)O2(‚) + RO2 f
Two reaction channels are open to the CH2Cl-CO(‚)Cl-CH2-
Cl radical, ejection of a Cl atom, or C-C bond scission:
CH2ClCHClC(O)O(‚) + RO + O2 (35)
CH2ClCHClC(O)O(‚) + M f
CH2ClCO(‚)ClCH2Cl + M f CH2ClCOCH2Cl + Cl + M
CH2ClC(‚)HCl + CO2 + M (36)
(27)
The observation of a significant yield of CO2 suggests, but
does not prove, that reaction 31 is an important loss fate of
CH2ClCHClCHClO(‚). At present we are unable to deduce the
atmospheric fate of CH2ClCHClCHClO(‚) radicals.
CH2ClCO(‚)Cl-CH2Cl + M f
CH2ClC(O)Cl + CH2Cl(‚) + M (28)
CH2ClCOCH2Cl product provides a marker for the importance
of reaction 27. CH2ClC(O)Cl product provides a marker for the
importance of reaction 28. It should be noted that in the presence
of NO there are no complications caused by CH2ClC(O)Cl
formation following decomposition of CH2ClCHClCHClO(‚)
radicals (see section 3.3). As seen from Table 2, the combined
yield of dichloroacetone and CH2ClC(O)Cl in the presence of
NOx (63 ( 6%) was indistinguishable from the yield of CH2-
Cl-CO(‚)Cl-CH2Cl radicals in the system; k3b/(k3a+k3b) ) (61
( 8%). We conclude that reactions 27 and 28 are competing
fates of CH2ClCO(‚)ClCH2Cl radicals formed in reaction 26.
Peroxy radical self-and cross reactions are the source of CH2-
ClCO(‚)ClCH2Cl radicals in the absence of NOx, e.g.,
4.2. Implications for Atmospheric Chemistry. We present
here the results of the first study of the atmospheric oxidation
mechanism of 1,2,3-trichloropropane. Atmospheric oxidation
will be initiated by reaction with OH radicals which is calculated
to proceed with a rate constant of 3.5 × 10-13 cm3 molecule-1
s-1 at 298 K.27 Assuming an atmospheric lifetime for methane
of 9 years34 and a rate constant for the CH4 + OH reaction of
6.3 × 10-15 cm3 molecule-1 s-1 leads to an atmospheric lifetime
for 1,2,3-trichloropropane against reaction with OH of 2 months.
Dichloroacetone is the major oxidation product with smaller
amounts of CH2ClC(O)Cl, HC(O)Cl, and CH2ClCHClC(O)Cl.
The atmospheric fate of dichloroacetone is photolysis which is
estimated to proceed at a rate of (5.6 ( 0.7) × 10-4 s-1 in the
sunlit atmosphere to produce HC(O)Cl. The atmospheric fate
of the acid chlorides CH2ClC(O)Cl, CH2ClCHClC(O)Cl, and
HC(O)Cl is expected to be incorporation into rain-cloud-
CH2ClCOO(‚)ClCH2Cl + CH2ClCOO(‚)ClCH2Cl f
2CH2ClCO(‚)ClCH2Cl + O2 (29)

5130 J. Phys. Chem. A, Vol. 105, No. 21, 2001
Voicu et al.
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fogwater followed by hydrolysis and removal by wet deposition
within probably 5-15 days.35 Hydrolysis of HC(O)Cl gives
formic acid which is a ubiquitous component of the environment
and is of no concern. Hydrolysis of CH2ClC(O)Cl and CH2-
ClCHClC(O)Cl gives monochloroacetic and 1,2-dichloroprop-
ionic acids. In spiked river water, biodegradation of monochlo-
roacetic acid was complete within 30 days,36 and it is likely
that degradation of 1,2-dichloropropionic acids will be equally
rapid. The atmospheric degradation of 1,2,3-trichloropropane
is unlikely to produce persistent organic pollutants.
Finally, the present work shows that chemical activation plays
a role in the atmospheric fate of CH2ClCHClO(‚) and CH2ClCO-
(‚)ClCH2Cl radicals. Activation effects have now been demon-
strated for several atmospherically important alkoxy radicals
and should be considered when assessing the atmospheric
oxidation mechanism of organic compounds.
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Fundamentals and Experimental Techniques, John Wiley and Sons: New
York, 1986.
Acknowledgment. Support of this work within the European
Commission 4th Framework Program project EUROSOLV and
by the Japanese Government with a NEDO grant is gratefully
acknowledged. We thank Geert Moortgat (Max-Planck Institute,
Mainz) for helpful discussions. T.J.W. thanks the Alexander
von Humboldt (AvH) Stiftung for an AvH Fellowship.
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