Atmospheric chemistry of fluorinated alcohols: Reaction with Cl atoms and OH radicals and atmospheric lifetimes

Article abstract of DOI:10.1021/jp0373088

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with a series of fluorinated alcohols, F(CF₂)_nCH₂OH (n = 1-4), in 700 Torr of N₂ or air diluent at 296 ± 2 K. The length of the F(CF₂)_n group had no discernible impact on the reactivity of the molecule. For n = 1-4, k(Cl + F(CF₂)_nCH₂OH) = (6.48 ± 0.53) × 10^-13 and k(OH + F(CF₂)_nCH₂OH) = (1.02 ± 0.10) × 10^-13 cm³ molecule^-1 s^-1. Product studies of the chlorine initiated oxidation of F(CF₂)_nCH₂OH (n = 1-4) in the absence of NO show the sole primary product to be the corresponding aldehyde, F(CF₂)_nC(O)H. Consideration of the likely rates of other possible atmospheric loss mechanisms leads to the conclusion that the atmospheric lifetime of F(CF₂)_nCH₂OH (n ≥ 1) is determined by reaction with OH radicals and is approximately 164 days.

Full text of DOI:10.1021/jp0373088

J. Phys. Chem. A 2004, 108, 1973-1979
1973
Atmospheric Chemistry of Fluorinated Alcohols: Reaction with Cl Atoms and OH Radicals
and Atmospheric Lifetimes
M. D. Hurley* and T. J. Wallington
Ford Motor Company, SRL-3083, PO Box 2053, Dearborn, Michigan 48121-2053
M. P. Sulbaek Andersen
Department of Chemistry, UniVersity of Copenhagen, UniVersitetsparken 5, DK-2100 Copenhagen, Denmark
D. A. Ellis, J. W. Martin, and S. A. Mabury
Lash Miller Chemical Laboratories, 80 St. George St., UniVersity of Toronto, Toronto,
Ontario, Canada M5S 3H6
ReceiVed: October 31, 2003; In Final Form: January 6, 2004
Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with a
series of fluorinated alcohols, F(CF2)nCH2OH (n ) 1-4), in 700 Torr of N2 or air diluent at 296 ( 2 K. The
length of the F(CF2)n group had no discernible impact on the reactivity of the molecule. For n ) 1-4,
k(Cl + F(CF2)nCH2OH) ) (6.48 ( 0.53) × 10-13 and k(OH + F(CF2)nCH2OH) ) (1.02 ( 0.10) × 10-13 cm3
molecule-1 s-1. Product studies of the chlorine initiated oxidation of F(CF2)nCH2OH (n ) 1-4) in the absence
of NO show the sole primary product to be the corresponding aldehyde, F(CF2)nC(O)H. Consideration of the
likely rates of other possible atmospheric loss mechanisms leads to the conclusion that the atmospheric lifetime
of F(CF2)nCH2OH (n g 1) is determined by reaction with OH radicals and is approximately 164 days.
1. Introduction
experiments. Chlorine atoms were produced by photolysis of
molecular chlorine
The detrimental effects of chlorine chemistry on stratospheric
ozone levels are well established.1,2 As a result, there has been
a concerted effort to find replacements for chlorofluorocarbons
(CFCs) used previously as electronic equipment cleaners, heat
transfer agents, refrigerants, and carrier fluids for lubricant
deposition. The replacements for CFCs, hydrofluorocarbons
(HFCs) and hydrofluorochlorocarbons (HCFCs), have found
widespread industrial use over the past decade. Fluorinated
ethers and fluorinated alcohols are new classes of compounds
currently under consideration for use as CFC replacements.
In light of the potential widespread use of fluorinated alcohols,
detailed information on the environmental impact of this class
of compounds is needed. In particular, there is a need to quantify
the potential for atmospheric oxidation of fluorinated alcohols
to act as a source of perfluorinated carboxylic acids.3 To improve
our knowledge of the atmospheric chemistry of fluorinated
alcohols in general and F(CF2)nCH2OH (n ) 1-4) in particular,
these compounds were studied using the smog chamber at the
Ford Motor Company. The kinetics and mechanism of their
simulated atmospheric oxidation was monitored using Fourier
transform infrared (FTIR) spectroscopy. Results are reported
herein.
Cl2 + hν f Cl + Cl
(1)
OH radicals were produced by the photolysis of CH3ONO in
air
CH3ONO + hν f CH3O + NO
CH3O + O2 f HO2 + HCHO
HO2 + NO f OH + NO2
(2)
(3)
(4)
Relative rate techniques were used to measure the rate constant
of interest relative to a reference reaction whose rate constant
has been established previously. Chlorine atom kinetics were
studied by irradiating Cl2/reactant/reference mixtures in air or
N2 diluent using UV fluorescent blacklamps. The relevant
reactions in the system were (1, 5, 6):
Cl + reactant f products
Cl + reference f products
(5)
(6)
In such experiments Cl atoms are in steady state and the loss
of reactant and reference are given by
2. Experimental Section
Experiments were performed in a 140-liter Pyrex reactor
interfaced to a Mattson Sirus 100 FTIR spectrometer.4 The
reactor was surrounded by 22 fluorescent blacklamps (GE
F15T8-BL) which were used to photochemically initiate the
[reactant]t
[reference]t
0
k
0
Ln
)
5Ln
(I)
(
)
(
)
k6
[reactant]t
[reference]t
where [reactant]t , [reactant]t, [reference]t , and [reference]t are
0
0
the concentrations of reactant and reference at times “t0” and
“t”, k5 and k6 are the rate constants for reactions 5 and 6. Plots
* To whom correspondence should be addressed. E-mail: mhurley3@
ford.com.
10.1021/jp0373088 CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/25/2004

1974 J. Phys. Chem. A, Vol. 108, No. 11, 2004
Hurley et al.
of Ln([reactant]t /[reactant]t) versus Ln([reference]t /[reference]t)
0
0
should be linear, pass through the origin, and have a slope of
k5/k6.
The loss of F(CF2)nCH2OH (n ) 1-4) and the reference
compounds were monitored by FTIR spectroscopy using an
analyzing path length of 27 m and a resolution of 0.25 cm-1
.
Infrared spectra were derived from 32 co-added interferograms.
The reactants are liquids and were introduced into the chamber
by transferring the vapor above the liquid via calibrated vol-
umes. The contents of the calibrated volumes were swept into
the chamber with the diluent gas (either air or nitrogen). The
concentration of reactants in the chamber was calculated
using the vapor pressure measured in the calibrated volumes.
Reactant and reference compounds were monitored using
absorption features over the following wavenumber ranges
(cm-1): F(CF2)nCH2OH, 3600-3700; CH3Cl, 1400-1550;
CH3OC(O)H, 1700-1800; and C2H2, 650-800. Initial reagent
concentrations for the Cl atom relative rate experiments were
9-13 mTorr of F(CF2)nCH2OH, 15-30 mTorr of the reference
compound CH3Cl, 8-12 mTorr of the reference compound
CH3OC(O)H, and 100-120 mTorr of Cl2 in 700 Torr of either
N2 or air diluent. In the OH radical experiments, the initial
reagent concentrations were 14-53 mTorr of F(CF2)nCH2OH,
2-10 mTorr of the reference compound C2H2, and 50-100
mTorr of CH3ONO in 700 Torr of air diluent. All experiments
were performed at 296 K. Reagents were obtained from
commercial sources at purities of >99% and were subjected to
repeated freeze-pump-thaw cycling before use. The fluorinated
aldehydes used for references in the product studies were
synthesized as described elsewhere5 and purified by vacuum
distillation. In smog chamber experiments, it is important to
check for unwanted loss of reactants and products via photolysis,
dark chemistry, and heterogeneous reactions. Control experi-
ments were performed in which mixtures of reactants (except
Cl2 or CH3ONO) in N2 were subjected to UV irradiation for
15-30 min and product mixtures obtained after the UV
irradiation of reactant mixtures were allowed to stand in the
dark in the chamber for 15 min. There was no observable loss
of reactants or reference compounds suggesting that photolysis,
dark chemistry, and heterogeneous reactions are not a significant
complication in the present work. Quoted uncertainties are two
standard deviations from least squares regressions.
Figure 1. Loss of F(CF2)nCH2OH (n ) 1, circles; n ) 2, triangles;
n ) 3, squares; n ) 4, diamonds) versus CH3Cl (closed symbols) and
CH3OCHO (open symbols) following UV irradiation of F(CF2)nCH2-
OH/reference/Cl2 mixtures in 700 Torr of N2 (n ) 1, 3, 4) or air (n )
2), diluent at 296 K.
1.30 ( 0.05 and k7/k9 ) 0.481 ( 0.020. Using k8 ) 4.8 ×
10-13 cm3 molecule-1 s-1 6 and k9 ) 1.4 × 10-12 cm3
molecule-1 s-1,7 we derive k7 ) (6.24 ( 0.24) × 10-13 and
(6.73 ( 0.28) × 10-13 cm3 molecule-1 s-1. Results obtained
using the two different reference compounds were, within the
experimental uncertainties, indistinguishable. The fact that
consistent values of k7 were derived from experiments using
different reference compounds and diluent gas suggests the
absence of significant systematic errors in the present work.
We choose to cite a final value for k7 which is the average of
the two determinations together with error limits which encom-
pass the extremes of the individual determinations. Hence,
k7 ) (6.48 ( 0.53) × 10-13 cm3 molecule-1 s-1
.
Papadimitriou et al.8 used a discharge-flow mass spectrometric
technique to determine the k(Cl + CF3CH2OH) ) (6.3 ( 0.9)
× 10-13 cm3 molecule-1 s-1 at 303 K. Kelly and Sidebottom9
used a relative rate method to measure k(Cl + CF3CH2OH) )
(7 ( 1) × 10-13 cm3 molecule-1 s-1 at 298 K. The result
obtained in the present work is indistinguishable, within
experimental uncertainties, from those obtained in previous
studies.
3. Results
3.1. Relative Rate Study of the Reaction of Cl Atoms with
F(CF2)nCH2OH. The kinetics of reactions 7 were measured
relative to reaction 8 and 9
It is instructive to compare our Cl atom reactivity results with
those for ethane, ethanol, and a series of fluorinated ethanols,
which is done in Table 1. At ambient temperature the reaction
of Cl atoms with CH3CH3 proceeds with a rate of (5.75 ( 0.46)
× 10-11 10 and with CH3CH2OH with a rate of (9.5 ( 1.9) ×
Cl + F(CF2)nCH2OH f products
Cl + CH3Cl f products
(7)
(8)
(9)
10-11 cm3 molecule-1 s-1 11
. Reaction with CH3CH2OH occurs
93% via H-atom abstraction from the CH2 group11 demonstrating
the activating influence of the OH group. As fluorine is
substituted for hydrogen on the methyl group, there is a dramatic
decrease in the reactivity of the molecule toward Cl atoms which
presumably reflects an increase in strength of the C-H bonds
in the CH2 group. Once the methyl group is fully fluorinated,
the addition of CF2 groups (i.e., C2F5 compared to CF3) has no
further effect on reactivity.
Cl + CH3OC(O)H f products
Experiments were performed in which the reactivity of Cl atoms
with F(CF2)nCH2OH (n ) 1-4) was measured relative to the
reactivity of CH3Cl and CH3OC(O)H. Figure 1 shows the loss
of F(CF2)nCH2OH versus the reference compounds following
UV irradiation of F(CF2)nCH2OH/Cl2/reference mixtures in air
(for n ) 2) or N2 (for n ) 1, 3, and 4) diluent. As seen in
Figure 1, there was no discernible effect of fluorinated chain
length or diluent gas on the kinetic data.
The insensitivity of the kinetics of reaction of Cl atoms with
F(CF2)nCH2OH to the length of the “fluorinated tail” is
consistent with a recent study by Ellis et al.3 of the reactivity
of a series of fluorotelomer alcohols, F(CF2CF2)nCH2CH2OH
(n ) 2-4) in which the reactivity of Cl atoms to the
The lines through the data in Figure 1 are linear least-squares
fits to the combined data sets which give values of k7/k8 )

Atmospheric Chemistry of Fluorinated Alcohols
J. Phys. Chem. A, Vol. 108, No. 11, 2004 1975
TABLE 1: Rate Constants for the Reaction of Cl Radicals with Ethane, Ethanol and a Series of Fluorinated Ethanols at
Ambient Temperature. (rate constants are in units of 10-13 cm3 Molecule-1 s-1
)
Tyndall et al.10
Taatjes et al.11
Papadimitriou et al.8
Kelly and Sidebottom9
this work
CH3CH3
CH3CH2OH
575 ( 46
950 ( 190
CH2FCH2OH
CHF2CH2OH
CF3CH2OH
CF3CF2CH2OH
CF3(CF2)2CH2OH
CF3(CF2)3CH2OH
196 ( 29
29.5 ( 3.9
6.3 ( 0.9
244 ( 25
7 ( 1
6.5 ( 0.5
6.5 ( 0.5
6.5 ( 0.5
6.5 ( 0.5
Figure 3. Products versus loss of CF3CH2OH for successive irradia-
tions of a mixture of 20 mTorr CF3CH2OH and 100 mTorr Cl2 in air.
The products observed are CF3C(O)H (closed circles), CF3C(O)OH
(open circles), COF2 (open triangles), CF3OH (open diamonds), and
CF3O3CF3 (open squares). Lines are included as a guide to the eye.
scribed above. The product profiles shown in Figure 3 are
consistent with CF3C(O)H being the main primary product and
CF3COOH, COF2, CF3OH, and CF3O3CF3 being secondary
products formed from the reaction of CF3C(O)H with Cl in air
Figure 2. IR spectra obtained before (A) and after (B) 60 s of
irradiation of a mixture of 20 mTorr CF3CH2OH and 100 mTorr Cl2 in
700 Torr air. The consumption of CF3CH2OH was 41%. Panels C, D,
and E are reference spectra of CF3C(O)H, CF3C(O)OH, and COF2,
respectively.
Cl + CF3CH2OH f CF3CHOH + HCl
CF3CHOH + O2 f R CF3C(O)H + HO2
Cl + CF3C(O)H f products
(10)
(11)
(12)
fluorotelomer alcohols was found to be k(Cl + F(CF2CF2)n-
CH2CH2OH) ) (1.61 ( 0.49) × 10-11 cm3 molec-1 s-1 for
n ) 2, 3, 4.
3.2. Product Study of the Cl + F(CF2)nCH2OH Reaction
in 700 Torr of Air. The Cl atom initiated oxidation of F(CF2)n-
CH2OH (n ) 1-4) was investigated by irradiating mixtures
containing 10-20 mTorr F(CF2)nCH2OH and 100 mTorr Cl2
in 700 Torr of air diluent. Figure 2 shows spectra acquired before
(A) and after (B) 60 s of irradiation of 20 mTorr CF3CH2OH
and 100 mTorr Cl2 in 700 Torr of air. Consumption of CF3-
CH2OH was 41% during irradiation. The IR features in panel
B can be compared with the IR spectra of CF3C(O)H, CF3-
COOH, and COF2 shown in panels C, D, and E, respectively.
Product features due to CF3OH and CF3O3CF3 were also
observed. For the irradiation of mixtures containing F(CF2)n-
CH2OH (n ) 2-4), in addition to the trioxide CF3O3CF3, there
are residual features which are similar to those of CF3O3CF3
and consistent with the mixed trioxides F(CF2)xO3(CF2)yF
(x ) 1-4, y ) 1-4).
The concentration profile of a reactive primary product can be
described12 by the expression
[CF3C(O)H]t
)
[CF3CH2OH]t
0
R
12/k10
(1 - x){(1 - x)(k )-1 - 1} (II)
{
}
(1 - (k12/k10))
where x ) 1 - ([CF3CH2OH]t/[CF3CH2OH]t ) (the fractional
0
consumption of CF3CH2OH at time t) and R is the yield of
CF3C(O)H from the reaction of Cl with CF3CH2OH in the
presence of oxygen. Figure 4 shows a plot of [CF3C(O)H]t/
[CF3CH2OH]t versus ∆[CF3CH2OH]t/[CF3CH2OH]t for two
0
0
experiments. A fit of eq II to the data in Figure 4 gives R )
0.97 ( 0.03 and k12/k10 ) 2.92 ( 0.15. Using the value for k10
determined in this study, (6.48 ( 0.53) × 10-13 cm3 molecule-1
Figure 3 shows the observed formation of CF3C(O)H, CF3-
COOH, COF2, CF3OH, and CF3O3CF3 versus the loss of CF3-
CH2OH following successive irradiations of the mixture de-
s-1, gives k12 ) (1.90 ( 0.25) × 10-12 cm3 molecule-1 s-1
.

1976 J. Phys. Chem. A, Vol. 108, No. 11, 2004
Hurley et al.
Figure 4. Plot of the observed concentration of CF3C(O)H normalized
to the initial CF3CH2OH concentration versus the fractional loss of CF3-
CH2OH following the irradiation of either 10 (triangles), 11.6 (circles),
or 20 mTorr (diamonds) CF3CH2OH and 100 mTorr Cl2 in 700 Torr
air. The line is a fit of equation II to the data. See text for details.
Figure 5. Product formation versus CF3C(O)H loss during successive
irradiations of a mixture of 20 mTorr CF3CH2OH and 100 mTorr Cl2
in air. The products observed are CF3C(O)OH (closed circles), COF2
(open triangles), CF3OH (open diamonds), and CF3O3CF3 (open
squares). The solid line is a second-order polynomial fit to the CF3C-
(O)OH profile. The initial CF3C(O)OH yield is 0.26 ( 0.01. The broken
lines are included as a guide to the eye.
TABLE 2: Results of Fitting Equation II to the
F(CF2)nCH2OH Primary Product Data
F(CF2)nC(O)H
yield
k(Cl + F(CF2)nC(O)H)
In all cases, the aldehyde, F(CF2)nC(O)H, was the sole
primary product of the reaction of F(CF2)CH2OH with Cl in
air. F(CF2)nCOOH, COF2, CF3OH, and CF3O3CF3 were ob-
served as secondary products. Since the aldehyde is formed in
100% yield, the amount of aldehyde that has reacted in the
system can be equated to the difference between the observed
loss of alcohol and the observed formation of aldehyde
k12/k10
cm3 molecule-1 s-1
CF3CH2OH
CF3CF2CH2OH
0.97 ( 0.03 2.92 ( 0.15 1.90 ( 0.25 × 10-12
1.01 ( 0.08 3.60 ( 0.36 2.35 ( 0.42 × 10-12
CF3(CF2)2CH2OH 1.01 ( 0.05 3.94 ( 0.22 2.56 ( 0.35 × 10-12
CF3(CF2)3CH2OH 1.02 ( 0.04 3.82 ( 0.17 2.48 ( 0.31 × 10-12
Experiments with F(CF2)nCH2OH (n ) 2-4) gave similar
results, which are summarized in Table 2. Again, within
experimental error, the reactivity of Cl toward the fluorinated
aldehydes are indistinguishable, and we chose to cite a final
value which is the average of individual values with error limits
which encompass the extremes of the individual measurements,
k(Cl + F(CF2)nC(O)H) ) (2.3 ( 0.7) × 10-12 cm3 molecule-1
∆F(CF2)nC(O)H ) ∆F(CF2)nCH2OH - F(CF2)nC(O)H
(III)
Hence, the formation of the secondary products can be plotted
versus the loss of the aldehyde. This plot is shown in Figure 5
for CF3C(O)H. The product profile of CF3COOH is curved with
an initial yield of 0.25 ( 0.02. The other observed products,
COF2, CF3OH, and CF3O3CF3, are those expected from
decomposition. Plots of F(CF2)nCOOH versus ∆F(CF2)nC(O)H
(n ) 2-4) give F(CF2)nCOOH yields of 0.18 ( 0.01, 0.07 (
0.01, and 0.06 ( 0.01 for n ) 2-4, respectively. Andersen et
al.15 have studied the reaction of CF3CF2C(O)O2 with HO2 and
report formation of CF3CF2C(O)OH in a yield of 24 ( 2%.
The slightly lower CF3CF2C(O)OH yield is probably attributable
to lower HO2 concentrations in the present study and the fact
that reaction with HO2 is not likely to be the sole fate of CF3-
CF2C(O)O2 radicals. The reason for the curved F(CF2)nCOOH
profiles is unclear. It is unlikely that the curvature is due to
reaction of the acids with Cl, considering that Andersen et al.15
established an upper limit for the rate constant of Cl atoms with
CF3CF2C(O)OH, k(Cl + CF3CF2C(O)OH) < 1 × 10-17 cm3
molecule-1 s-1. Curvature is more likely to be caused by a
decrease of the HO2 radical concentration during the period of
the experiment.
s-1
.
There are three previous measurements of the reactivity of
Cl toward perfluorinated aldehydes. Wallington et al.13 used a
relative rate technique to determine k(Cl + CF3C(O)H) )
(1.79 ( 0.4) × 10-12 cm3 molecule-1 s-1, whereas Scollard et
al.,14 also using relative rate techniques, determined k(Cl +
CF3C(O)H) ) (2.71 ( 0.11) × 10-12 cm3 molecule-1 s-1. In a
recent paper, Andersen et al.5 used relative rate techniques to
determine k(Cl + CF3CF2C(O)H) ) (1.97 ( 0.28) × 10-12 cm3
molecule-1 s-1. The studies of Wallington et al.13 and Andersen
et al.5 were conducted in the absence of O2, whereas as discussed
elsewhere,13 that of Scollard et al.14 may have been conducted
in the presence of O2. The presence of O2 is an important
consideration as it will lead to the formation of CF3O radicals
which are likely to react with the fluorinated aldehyde. Hence,
to the extent that CF3O radical chemistry contributes to the loss
of F(CF2)nC(O)H, relative rate experiments conducted in the
presence of O2 will probably overestimate k(Cl + F(CF2)nC-
(O)H). Accordingly, the values given in Table 2 should be
considered upper limits for k(Cl + F(CF2)nC(O)H). Finally, in
light of the fact that the values of k(Cl + F(CF2)nC(O)H) for
n ) 1 and 2 in Table 2 are indistinguishable from those of
Wallington et al.13 and Andersen et al.5 obtained in N2 diluent,
it seems likely that the magnitude of the any unwanted CF3O
chemistry is modest.
The observed products from the Cl initiated oxidation of CF3-
CH2OH are consistent with the following reactions. Reaction
of F(CF2)nCH2OH (n ) 1-4) is initiated by the abstraction of
hydrogen, followed by reaction with oxygen, leading to forma-
tion of the aldehyde, F(CF2)nC(O)H

Atmospheric Chemistry of Fluorinated Alcohols
J. Phys. Chem. A, Vol. 108, No. 11, 2004 1977
F(CF2)nCH2OH + Cl f F(CF2)nCHOH + HCl (13)
F(CF2)nCHOH + O2 f F(CF2)nC(O)H + HO2 (14)
Cl then abstracts the aldehydic hydrogen from F(CF2)nC(O)H,
which reacts with oxygen to form the peroxy radical, F(CF2)n-
C(O)O2
F(CF2)nC(O)H + Cl f F(CF2)nC(O) + HCl
F(CF2)nC(O) + O2 f F(CF2)nC(O)O2
(15)
(16)
The peroxy radical reacts with HO2 to form the perfluorinated
carboxylic acid and ozone. HO2 radicals can react with other
HO2 radicals, whereas the alkyl peroxy radical can react with
other peroxy radicals to form the alkoxy radical
F(CF2)nC(O)O2 + HO2 f F(CF2)nC(O)OH + O3 (17)
HO2 + HO2 f H2O2 + O2
(18)
Figure 6. Loss of F(CF2)nCH2OH (n ) 1, circles; n ) 2, triangles;
n ) 3, squares; n ) 4, diamonds) versus the reference compound, C2H2,
following UV irradiation of F(CF2)nCH2OH/reference/CH3ONO mix-
tures in 700 Torr air diluent at 296 K.
F(CF2)nC(O)O2 + RO2 f F(CF2)nC(O)O + RO + O2 (19)
Reaction 19 leads to decomposition of F(CF2)nC(O)O, first
through the elimination of CO2 followed by reaction with
oxygen to form the peroxy radical, F(CF2)nO2
can be seen from Figure 6 that there is no discernible difference
in the reactivity of F(CF2)nCH2OH (n ) 1-4) relative to the
reference. The line through the data in Figure 6 is a linear least-
F(CF2)nC(O)O f F(CF2)n + CO2
F(CF2)n + O2 f F(CF2)nO2
(20)
(21)
squares fit to the combined data sets which gives k26/k27
)
)
0.12 ( 0.01. Using k27 ) 8.5 × 10-13 16
,
we derive k26
(1.02 ( 0.10) × 10-13 cm3 molecule-1 s-1
.
Reaction of F(CF2)nO2 with other peroxy radicals leads to
the formation of alkoxy radicals, F(CF2)nO, which are known
to eliminate COF2
The reactivity of OH toward CF3CH2OH has been measured
previously. Wallington et al.17 used a flash photolysis technique
to measure the absolute rate constant and reported k(OH +
CF3CH2OH) ) (9.55 ( 0.66) × 10-14 cm3 molecule-1 s-1
.
F(CF2)nO2 + RO2 f F(CF2)nO + RO + O2
(22)
Tokuhashi et al.18 used absolute rate techniques and reported
k(OH + CF3CH2OH) ) (1.00 ( 0.04) × 10-13 and k(OH +
CF3CF2CH2OH) ) (1.02 ( 0.04) × 10-13 cm3 molecule-1 s-1
.
F(CF2)nO f F(CF2)n-1 + COF2 (n > 1)
(23)
Chen et al.19 used the relative rate technique and derived
k(OH + CF3CF2CH2OH) ) (1.15 ( 0.08) × 10-13 cm3
molecule-1 s-1. There is excellent consistency in the kinetic
database for reaction of OH radicals with alcohols of the general
formula F(CF2)nCH2OH. It is clear that there is no effect of
fluorinated chain length on the reactivity of these molecules
and that k(OH + F(CF2)nCH2OH) ≈ 1.0 × 10-13 cm3
Repetition of reactions 21, 22, and 23 results in the unzipping
of the radical and the formation of n - 1 molecules of COF2
for F(CF2)nCH2OH (n ) 1-4). The last radical formed, CF3O,
reacts with CF3O2 to form the trioxide, CF3O3CF3, or abstracts
a H-atom from a hydrogen containing molecule (e.g., F(CF2)n-
C(O)H, H2O2, HCl) or radical (e.g., HO2) in the system
molecule-1 s-1
.
CF3O + HO2 f CF3OH + O2
(24)
4. Atmospheric Implications
Another fate of alkoxy and peroxy radicals formed in
reactions 18-20 is reaction to form trioxides
The value of k(OH + F(CF2)nCH2OH) (n ) 1-4) measured
here can be used to provide an estimate of the atmospheric
lifetime of F(CF2)nCH2OH with respect to reaction with OH
radicals by scaling to CH3CCl3. The optimal temperature for
such a scaling analysis is 272 K20 rather than 296 K used here.
The Arrhenius rate constant of CH3CCl3 has been determined
to be k(OH + CH3CCl3) ) 1.6 × 10-12 exp(-1520/T).6
Although we do not have kinetic data for k26 at 272 K, it is
reasonable to assume a temperature dependence similar to CF3-
CF2CH2OH. Tokuhashi et al.18 determined the Arrhenius rate
constant of CF3CF2CH2OH to be k(OH + CF3CF2CH2OH) )
(1.40 ( 0.27) × 10-12 exp[-(780 ( 60)/T]. Using these two
Arrhenius expressions, the rate constants at 272 K are calculated
to be k(OH + CH3CCl3) ) 6.0 × 10-15 cm3 molecule-1 s-1
and k(OH + F(CF2)nCH2OH) ) 8.0 × 10-14 cm3 molecule-1
s-1. Assuming an atmospheric lifetime for CH3CCl3 with respect
to reaction with OH radicals of 5.99 years21 leads to an estimate
of the atmospheric lifetime of F(CF2)nCH2OH (n ) 1-4) of
F(CF2)nOO + F(CF2)nO f F(CF2)nO3(CF2)nF (25)
CF3O3CF3 was an observed product. Small unidentified residual
IR features were present in the product spectra. The residual
spectra were similar to CF3O3CF3 and indicate the presence of
higher trioxides.
3.3. Relative Rate Study of the Reaction of OH Radicals
with F(CF2)nCH2OH. The reactivity of OH radicals toward
F(CF2)nCH2OH (n ) 1,2,3,4) was studied relative to reac-
tion 24
OH + F(CF2)nCH2OH f products
OH + C2H2 f products
(26)
(27)
Figure 6 shows the loss of F(CF2)nCH2OH versus the loss of
the reference compound, C2H2, on exposure to OH radicals. It

1978 J. Phys. Chem. A, Vol. 108, No. 11, 2004
Hurley et al.
TABLE 3: Physicochemical Properties of F(CF2)2CH2OH Used in EQC Level III Calculations
molar mass
(g/mol)
Henry’s law constant, Kh
water solubilitya
(g/m3)
vapor pressure
(Pa)
melting point
half-life τOH
(Pa m3/mol)
log KOW
(°C)
(h)
b
150
7.2
98 000
4700
2.6
-56
1900
b
a Calculated water solubility from KH and Vp. Kow for F(CF2)2CH2OH assumed to be similar order of magnitude as F(CF2)3CH2OH.
sphere, loss processes such as partition to aerosols (1.55 × 10-6
TABLE 4: Half-Times for Partition between Environmental
%), dry deposition (10 m/h), and rainout (1 × 10-4 m/h) are
Phases
insignificant processes compared with OH reaction and direct
air-water partition.
partition
air to water
air to soil
half-time (days)
73.9
556
It is worth noting that as the fluorocarbon chain length
increases for the alcohols the air-water partition is expected
to decrease, and hence, OH kinetics will start to govern, as was
found to be the case for fluorotelomer alcohols.3 Furthermore,
in geographic locations with little or no bodies of water, OH
reactions will completely predominate.
Loss of F(CF2)nCH2OH n > 4 via wet deposition, dry
deposition, photolysis, or reaction with atmospheric constituents
other than OH is expected to be of minor importance. The
atmospheric lifetime of F(CF2)nCH2OH is determined by
reaction with OH radicals and is approximately 164 days. As
discussed above, the atmospheric oxidation of F(CF2)nCH2OH
gives small, but significant yields of perfluorocarboxylic acids,
F(CF2)nC(O)OH. In light of the toxic29 and bioacculumative30-32
nature of long (>C6) chain perfluorocarboxylic acids, further
studies of the atmospheric chemistry and environmental impact
of long (>C6) chain F(CF2)nCH2OH are needed prior to any
large scale industrial use.
water to air
water to sediments
soil to air
51.3
4640
359
soil to water
486
(6.0 × 10-15)/(8.0 × 10-14) × 5.99 × 365 ) 164 days. The
approximate nature of the atmospheric lifetime estimate provided
here should be stressed. The average daily concentration of OH
radicals in the atmosphere varies significantly with both location
and season.22 The estimates presented here are for the global
average lifetime with respect to reaction with OH radicals.
The calculated behavior of a chemical in a model environment
provides a basis for evaluating its environmental fate. The
equilibrium criterion or EQC model23 is a widely used evaluative
model that treats an area of 105 km2 with 10% of the area being
covered by water. This model has been used for the evaluation
of the environmental dissemination of fluorinated aromatics.24
The temperature in the EQC environment is set at 25 °C, which
is a common temperature at which physicochemical properties
are measured. An evaluation of the atmospheric fate of F(CF2)2-
CH2OH was conducted using this model. The EQC level III
model allows nonequilibrium conditions to exist between
connected media at steady state. The output data is useful in
determining how the media of release affects environmental fate
and can also identify important transformation and interphase
partition processes.25 The model requires the input of key
physicochemical data for the fluorinated alcohol, which are
given in Table 3. For F(CF2)2CH2OH, the required physico-
chemical data appears in the literature,26-28 limiting the necessity
for assumptions concerning these to be made. The atmospheric
fate of the alcohol has been assessed solely through direct input
into that compartment.
Acknowledgment. M.P.S.A. thanks the Danish Research
Agency for a research grant.
References and Notes
(1) Molina, M. J.; Rowland, F. S. Nature 1974, 249, 810.
(2) Farman, J. D.; Gardiner, B. G.; Shanklin, J. D. Nature 1985, 315,
207.
(3) Ellis, D. A.; Martin, J. W.; Mabury, S. A.; Hurley, M. D.; Sulbaek
Andersen, M. P.; Wallington, T. J. EnViron. Sci., Technol. 2003, 37, 3816.
(4) Wallington, T. J.; Japar, S. M. J. Atmos. Chem. 1989, 9, 399.
(5) Sulbaek Andersen, M. P.; Hurley, M. D.; Wallington, T. J.; Ball,
J. C.; Martin, J. W.; Ellis, D. A.; Mabury, S. A.; Nielsen, O. J. Chem.
Phys. Lett. 2003, 379, 28.
(6) Sander, S. P.; Friedl, R. R.; Golden, D. M.; Kurylo, M. J.; Huie,
R. E.; Orkin, V. L.; Moortgat, G. K.; Ravishankara, A. R.; Kolb, C. E.;
Molina, M. J.; Finlayson-Pitts, B. J. JPL Publication No. 02-25; NASA
Jet Propulsion Lab.: Pasadena, California, 2003.
(7) Wallington, T. J.; Hurley, M. D.; Ball, J. C.; Jenkin, M. E. Chem.
Phys. Lett. 1993, 211, 41.
(8) Papadimitriou, V. C.; Prosmitis, A. V.; Lararou, Y. G.; Papagian-
nakopoulos, P. J. Phys. Chem. A 2003, 107, 3733.
The half-life (t1/2) of a chemical, which is defined as the time
required for the concentration of a reactant to fall to one-half
of its initial concentration, is a required parameter of this model.
The half-life of the fluorinated alcohols is given by the following
equation:
(9) Kelly, T.; Sidebottom, H. A kinetic and mechanistic study of the
atmospheric oxidation of 3,3,3-trifluoropropanol. PosterCMD-2; Presented
at the Eurotrac 2 Symposium, Garmisch-Partenkirchen, March 2002 (http://
imk-aida.fzk.de/CMD/AR2001/GPP18_4.pdf).
0.693
t1/2
)
) 1887 h
k(OH + F(CF2)2CH2OH)[OH]
(10) Tyndall, G. S.; Orlando, J. J.; Wallington, T. J.; Dill, M.; Kaiser,
E. W. Int. J. Chem. Kinet. 1997, 29, 43.
(11) Taatjes, C. A.; Christensen, L. K.; Hurley, M. D.; Wallington, T.
J. J. Phys. Chem. A 1999, 103, 9805.
(12) Meagher, R. J.; McIntosh, M. E.; Hurley, M. D.; Wallington, T. J.
Int. J. Chem. Kinet. 1997, 29, 619.
(13) Wallington, T. J.; Hurley, M. D. Int. J. Chem. Kinet. 1993, 25,
819.
(14) Scollard, D. J.; Treacy, J. J.; Sidebottom, H. W.; Balestra-Garcia,
C.; Laverdet, G.; LeBras, G.; MacLeod, H.; Teton, S. J. Phys. Chem. 1993,
97, 4683.
(15) Sulbaek Andersen, M. P.; Hurley, M. D.; Wallington, T. J.; Ball,
J. C.; Martin, J. W.; Ellis, D. A.; Mabury, S. A. Chem. Phys. Lett. 2003,
381, 14.
where k(OH + F(CF2)2CH2OH) ) 1.02 × 10-13 cm3 molecule-1
s-1 and [OH] ) 1 × 106 cm-3. Due to the relatively long half-
life of this alcohol from reaction with OH (t1/2 ) 1887 h) and
taken in conjunction with the KH of the alcohol (7.24 Pa m3/
mol), interphase partition phenomena, particularly air-water
partitioning (t1/2 ) 1773 h), is comparable in importance with
OH kinetics. The model indicates that the overall distribution
of F(CF2)2CH2OH due to this process would be 74.6%:25.4%
(air:water ratio). The model indicates that partitioning from
water to sediment is expected to be an insignificant process.
The calculated half-times for partitioning between environ-
mental compartments are given in Table 4. Within the atmo-
(16) Sorensen, M.; Kaiser, E. W.; Hurley, M. D.; Wallington, T. J.;
Nielsen, O. J. Int. J. Chem Kinet. 2003, 35, 191.

Atmospheric Chemistry of Fluorinated Alcohols
J. Phys. Chem. A, Vol. 108, No. 11, 2004 1979
(17) Wallington, T. J.; Dagaut, P.; Kurylo, M. J. J. Phys. Chem. 1988,
92, 5024.
(18) Tokuhashi, K.; Nagai, H.; Takahashi, A.; Kaise, M.; Kondo, S.;
Sekiya, A.; Takahashi, M.; Gotoh, Y.; Suga, A. J. Phys. Chem. A 1999,
103, 2664.
(19) Chen, L.; Fukuda, K.; Takenaka, N.; Bandow, H.; Maeda, Y. Int
J. Chem. Kinet. 2000, 32, 73.
(20) Spivakovsky, C. M.; Logan, J. A.; Montzka, S. A.; Balkanski, Y.
L.; Foreman-Fowler, M.; Jones, D. B. A.; Horowitz, L. W.; Fusco, A. C.;
Brenninkmeijer, C. A. M.; Prather, M. J.; Wofsy, S. C.; McElroy, M. B. J.
Geophys. Res. 2000, 105, 8931.
(24) Ellis, D. A.; Cahill, T. M.; Mabury S. A.; Cousins, I.; MacKay, D.
Partitioning of Organofluorine Compounds in the Environment. In The
Handbook of EnVironmental Chemistry; Neilson, A., Ed.; 2002; Vol 3, Part
N, pp 63-83.
(25) Mackay, D. Multimedia EnVironmental Models: The Fugacity
Approach, 2nd ed.; Lewis Publishers: Boca Raton, FL, 2001.
(26) Chen, L.; Takenaka, N.; Bandow, H.; Maeda, Y. Atmos. EnViron.
2003, 37, 4817.
(27) Oman, C. EnViron. Sci. Technol. 2001, 35, 232.
(28) Meeks, A. C.; Goldfarb, I. J. J. Chem. Eng. Data 1967, 12, 196.
(21) Prinn, R. G.; Huang, J.; Weiss, R. F.; Cunnold, D. M.; Fraser, P.
J.; Simmonds, P. G.; McCulloch, A.; Harth, C.; Salameh, P.; O’Doherty,
S.; Wang, R. H. J.; Porter, L.; Miller B. R. Science 2001, 292, 1882.
(22) Klecrnka, G.; Boethling, R.; Franklin, J.; Grady, L.; Howard, P.
H.; Kannan, K.; Larson, R. J.; Mackay, D.; Muir, D.; van de Meent, D.
EValuation of Persistence and Long-Range Transport of Organic Chemicals
in the EnVironment; SETAC Press: Pensacola, FL, 2000; p 45, ISBN
1-880611-22-8.
(29) USEPA. Preliminary Risk Assessment of the DeVelopmental Toxicity
Associated with Exposure to Perfluorooctanoic Acid (PFOA) and its Salts;
OPPT, Risk Assessment Division: Washington, DC, 2003.
(30) Moody, C. A.; Martin, J. W.; Kwan, W. C.; Muir, D. C. G.; Mabury,
S. A.; EnViron. Sci. Technol. 2002, 36, 545.
(31) Moody, C. A.; Kwan, W. C.; Martin, J. W.; Muir, D. C. G.; Mabury,
S. A. Anal. Chem. 2001, 73, 2200.
(32) Martin, J. W.; Smithwick, M. M.; Braune, B. M.; Hekstra, P. F.;
Muir, D. C. G.; Mabury, S. A. EnViron. Sci. Technol. 2004, 38, 373.
(23) Mackay, D.; Di Guardo, A.; Paterson, S.; Cowan, C. EnViron.
Toxicol. Chem. 1996, 15, 1627.