halogen elimination channel thermochemically favorable for
vinyl halides containing Cl or Br, but not F. This may serve to
explain the marked difference in observed reaction pathways
Photolysis of CF
3 3
CHO gives CF and HCO radicals while
reaction with OH, which is of lesser importance, but also
3
represents a sink for CF CHO, gives CF CO radicals. Atmo-
0
3
3
1
1
for t-CF CHQCHCl, when compared to t-CF CHQCHF.
spheric degradation routes by which CF CO radicals can be
3
3
3
Based on heat of formation, prop-1-en-1-ol has been calculated
to be less stable than its corresponding oxo form, propanal, and
will exist only in negligible amounts in a keto–enol mixture,
but the keto–enol tautomerization has a significant energy
transformed into CF COOH (TFA) as a minor (o10%)
3
3
product have been documented. TFA is a natural trace
1
3
2
component of the oceanic environment and any additional
burden from t-CF CHQCHCl oxidation will be negligible.
The remaining oxidation fragments will be converted into CO
3
27
barrier in the uncatalysed gas-phase. It is thus unclear if our
2
3
3
enol tautomer, CF CHQCHOH, which may also be stabilized
3
and HF through oxidation and hydrolysis. No long-lived
chlorine containing oxidation products were identified in
through fluorine mediated hydrogen bonding, would tauto-
merize to the aldehyde configuration. IR features belonging to
3
the OH radical initiated oxidation of t-CF CHQCHCl. The
3 2
CF CH CHO were sought in the product spectra but were not
atmospheric fate of the hypothesized oxidation product,
observed. However, reaction of OH radicals with CF CH CHO
3
CF CHQCHOH, is likely reaction with OH (directly, or
2
,10
3
4
proceeds quickly k(OH + CF CH CHO)/k E 6,
and
indirectly via reaction with the tautomer CF CH CHO) to
3
3
2
1
2
would render the detection of CF CH CHO in the present
3
yield CF CHO, HCHO and HCOOH. With an estimated
3
2
4
system difficult. If CF CHQCHOH is stable in the chamber,
atmospheric lifetime of 26 days for t-CF CHQCHCl, any
3
3
reaction of OH radicals with CF
proceed rapidly through addition of OH radicals to the carbon–
carbon double bond, followed by reaction with O and/or
decomposition to yield, CF CHO, HCHO and HCOOH.
Unfortunately, HCHO and HCOOH are also byproducts of
the photolysis of CH ONO, rendering these species of no value
as further evidence for the formation of CF CHQCHOH.
3
CHQCHOH is expected to
3
contribution from t-CF CHQCHCl oxidation to the strato-
spheric Cl atom loading will be insignificant (the Ozone
2
Depletion Potential (ODP) has recently been estimated at
3
0.00034 ). At the anticipated levels in the environment, the
4
3
3
atmospheric oxidation products of t-CF CHQCHCl are not
of concern.
3
3
Acknowledgements
4
. Atmospheric implications
We thank R. Singh (Honeywell International Inc.) for provid-
ing the t-CF CHQCHCl samples used in this study and S. P.
We present the results of the first study of the atmospheric
oxidation mechanism of t-CF CHQCHCl. The major products
in the Cl atom initiated oxidation of t-CF CHQCHCl were
, minor products were
COCl. Chemical activation
CHClCHClO,
CHClO, radicals in the
3
Sander (JPL) for helpful discussions. We thank N. Prisle and
F. F. Østerstrøm (University of Copenhagen) for assistance in
the experimental work. O.J.N. acknowledges financial support
from the Danish Natural Science Research Councilthe Villum
Kann Rasmussen Foundation and EUROCHAMP2. This
work was performed partly at the Jet Propulsion Laboratory,
California Institute of Technology, under a contract with the
National Aeronautics and Space Administration. M.P.S.A. is
supported by an appointment to the NASA Postdoctoral
Program, administered by Oak Ridge Associated Universities
through a contract with NASA. Copyright 2011.
3
3
CF
CF
3 3 2
CHClCHO and CF C(O)CHCl
3
CHO, HCOCl and CF
3
plays a significant role in the fate of CF
CF CH(O)CHCl , and possibly CF
3
3
2
3
system. The dominant atmospheric fate of t-CF CHQCHCl is
addition of OH radicals to the {CQCz double bond. The
OH radical initiated oxidation of t-CF CHQCHCl in one
3
atmosphere of air gives CF CHO and HCOCl in molar yields
3
3
of approximately 60%. Chamber experiments indicate a signi-
ficant decomposition channel involving chlorine elimination
3
with formation of the fluorinated enol CF CHQCHOH,
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2
8
probably 5–15 days. Hydrolysis of HCOCl gives formic acid
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of no concern. The dominant fate of CF CHO is photolysis
3
2
9
resulting in an estimated atmospheric lifetime of r2 days.
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Phys. Chem. Chem. Phys., 2012, 14, 1735–1748 1747