Arrhenius parameters for the OH-initiated degradation of methyl crotonate, methyl-3,3-dimethyl acrylate, (: E)-ethyl tiglate and methyl-3-butenoate over the temperature range of 288-314 K

Article abstract of DOI:10.1039/c6ra10279d

The relative-rate technique has been employed to obtain rate coefficients for the reactions between the OH radical and four unsaturated esters (methyl crotonate (k₁), methyl-3,3-dimethyl acrylate (k₂), (E)-ethyl tiglate (k₃) and methyl-3-butenoate (k₄)) between 288 and 314 K in 760 Torr of synthetic air. The experiments were performed in a multiple-pass environmental chamber with in situ FTIR detection of the esters and reference compounds. The rate coefficients for the reactions displayed a negative dependence with temperature and low pre-exponential factors. The following Arrhenius expressions (in units of cm³ per molecule per s) were obtained: k₁ = (3.39 ± 0.78) × 10^-12exp[(750 ± 159)/T], k₂ = (2.95 ± 0.63) × 10^-12exp[(838 ± 182)/T], k₃ = (1.49 ± 0.56) × 10^-12exp[(522 ± 114)/T] and k₄ = (1.90 ± 1.25) × 10^-12exp[(834 ± 185)/T]. The kinetic results are in agreement with a mechanism involving mainly OH radical addition to the double with the reversible formation of an OH-adduct. Atmospheric implications are discussed with particular reference to the rate coefficients obtained as a function of the temperature.

Full text of DOI:10.1039/c6ra10279d

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PAPER
Arrhenius parameters for the OH-initiated
degradation of methyl crotonate, methyl-3,3-
dimethyl acrylate, (E)-ethyl tiglate and methyl-3-
butenoate over the temperature range of 288–314 K†
Cite this: RSC Adv., 2016, 6, 53723
a
a
a
b
b
Juan P. Colomer, Marıa B. Blanco, Alicia B. Penenory, Ian Barnes, Peter Wiesen
˜´˜
´
a
and Mariano A. Teruel*
The relative-rate technique has been employed to obtain rate coefficients for the reactions between the OH
radical and four unsaturated esters (methyl crotonate (k ), methyl-3,3-dimethyl acrylate (k ), (E)-ethyl tiglate
) and methyl-3-butenoate (k )) between 288 and 314 K in 760 Torr of synthetic air. The experiments were
1
2
(k
3
4
performed in a multiple-pass environmental chamber with in situ FTIR detection of the esters and reference
compounds. The rate coefficients for the reactions displayed a negative dependence with temperature and
3
low pre-exponential factors. The following Arrhenius expressions (in units of cm per molecule per s) were
ꢂ12
ꢂ12
obtained: k
1
¼ (3.39 ꢀ 0.78) ꢁ 10
exp[(750 ꢀ 159)/T], k
2
¼ (2.95 ꢀ 0.63) ꢁ 10
exp[(838 ꢀ 182)/T], k ¼
3
Received 20th April 2016
Accepted 25th May 2016
ꢂ12
ꢂ12
(1.49 ꢀ 0.56) ꢁ 10
exp[(522 ꢀ 114)/T] and k
4
¼ (1.90 ꢀ 1.25) ꢁ 10
exp[(834 ꢀ 185)/T]. The kinetic
results are in agreement with a mechanism involving mainly OH radical addition to the double with the
reversible formation of an OH-adduct. Atmospheric implications are discussed with particular reference
to the rate coefficients obtained as a function of the temperature.
DOI: 10.1039/c6ra10279d
www.rsc.org/advances
7
radicals and O
3
molecules. To determine the impact of these
Introduction
compounds on air quality, kinetic and mechanistic data on
7
Unsaturated esters are emitted to the atmosphere by biogenic their tropospheric degradation are needed.
1
sources (as the emissions from agricultural crops, aer leaf
In this work, we report relative kinetic determinations of rate
2
wounding ) and by anthropogenic sources including the poly- coefficients for the reactions of OH radicals with methyl croto-
mer industry where they are widely used in the production of nate (MC) (1), methyl-3,3-dimethyl acrylate (MDMA) (2), (E)-ethyl
3
plastic and resins.
tiglate (ET) (3) and methyl-3-butenoate (M3B) (4) measured in an
Moreover, acrylates and methacrylates are among the most FTIR multiple-pass photoreactor between 288 and 314 K:
prevalent industrial organic chemicals in the world as dened
4,5
by the High Production Volume Chemicals list.
These
(
1)
compounds are employed as intermediates in the manufacture
of polymers and plastics and are also used as fuels and oil
additives. The most important polymer types are cast acrylic
sheets and molding/extrusion compounds, in addition to
6
emulsions, dispersions, and solvent-based polymers.
(2)
The release of these oxygenated volatile organic compounds
into the atmosphere is likely to contribute to the formation of
ozone, peroxy acetyl nitrate (PAN) and other components of
photochemical smog formed in urban areas mainly through
their reactions with OH radicals and other oxidants such as NO
3
(
(
3)
4)
a
Instituto de Investigaciones en Fisicoqu ´ı mica de C ´o rdoba (I.N.F.I.Q.C.), CONICET.
Facultad de Ciencias Qu ´ı micas, Universidad Nacional de C ´o rdoba. Ciudad
Universitaria, 5000 C ´o rdoba, Argentina. E-mail: mteruel@fcq.un.edu.ar
b
Bergische Universit a¨ t Wuppertal, Fakult a¨ t f u¨ r Mathematik und Naturwissenschaen,
Physikalische & Theoretische Chemie, 42119 Wuppertal, Germany
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c6ra10279d
1
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The rate coefficients for the reactions of these unsaturated
esters with OH radicals and Cl atoms have been reported at
atmospheric pressure and room temperature previously by our
CH O + O / CH O + HO
(6)
(7)
3
2
2
2
8,9
2 2
HO + NO / OH + NO
research group. As noted above, the atmospheric degradation
of unsaturated esters is mainly initiated by reaction with OH
radicals but information regarding the degradation processes is
still limited. To evaluate the impact of these reactions on the
formation of photo-oxidants and consequently on human
health and the environment, a thorough understanding of the
atmospheric oxidation processes of these compounds is
needed. Therefore, in line with our previous work and to obtain
a better understanding of the OH-radical mediated oxidation of
these compounds in the atmosphere we report here a study on
the temperature dependence of the kinetics of these reactions
with OH radicals. To the best of our knowledge, this work
provides the rst kinetic study for the reaction of OH radicals
with these unsaturated esters as a function of temperature.
Furthermore, residence times of the esters studied as a function
of the altitude of the troposphere are developed.
The initial concentrations employed in the experiments for
the unsaturated esters and reference compounds in ppm
1
3
3
(
1 ppm ¼ 2.46 ꢁ 10 molecule per cm at 298 K and 760 Torr of
total pressure) were as follows: ꢃ5.3 for methyl crotonate;
ꢃ3.9 for methyl-3,3-dimethyl acrylate; ꢃ3.7 for (E)-ethyl tiglate;
ꢃ4.8 for methyl-3-butenoate and 5–22 for 1-butene. The
concentration of CH
ppm for NO.
The evolution of the reactions was monitored by following
3
ONO was typically around 5 ppm and
3
the infrared absorption frequencies of the reactants at the
ꢂ1
following infrared frequencies (in cm ): methyl crotonate at
1
1
190; methyl-3,3-dimethyl acrylate at 1159; (E)-ethyl tiglate at
266; methyl-3-butenoate at 1176 and 1-butene at 912.
Materials
Experimental
The following chemicals, with purities as given by the manufac-
turer, were used in the experiments without further purication:
synthetic air (Air Liquide, 99.999%), methyl crotonate (Aldrich,
The experiments were carried out in a quartz-glass reaction
chamber (1080 L) in synthetic air at a total pressure of 760 ꢀ 10
Torr (760 Torr ¼ 101.325 kPa) over the temperature range 288–
98%), methyl-3,3-dimethyl acrylate (Aldrich, 97%), (E)-ethyl
tiglate (Aldrich, >98%), methyl-3-butenoate (Aldrich, 95%), 1-
butene (Messer Griesheim, 99%), NO (Messer Griesheim, 99%).
314 K. Since a detailed description of the reaction chamber can
10
be found in previous work only the basic features are outlined
here.
Methyl nitrite was synthesized according to the method of
11
Taylor et al. by the dropwise addition of 50% H SO4 to
2
ꢂ3
The reactor can be evacuated to 10 Torr using a pumping
a saturated solution of NaNO in methanol and was puried by
2
system comprised of a turbo-molecular pump backed by
a double-stage rotary fore pump. To ensure a homogeneous
distribution of the substrates inside the chamber three
vacuum distillation.
magnetically coupled Teon mixing fans were employed. The Results and discussion
reactor is surrounded by 32 individually switched superactinic
Rate coefficients for the reactions of OH radicals with MC,
MDMA, ET and M3B were determined over the range 288–314 K
by comparing their rates of decay with that of the corresponding
decay of a reference compound:

uorescent lamps (Philips TL05 40 W, l ¼ 320–480 nm, lmax
¼
360 nm), which are wired in parallel and spaced evenly around
the reaction vessel thus allowing variation of the light intensity
and consequently the photolysis frequency/radical production
rate within the chamber. A multiple-reection white-type mirror
system with a base length of 5.91 ꢀ 0.01 m is installed in the
reactor for sensitive “in situ” long path absorption monitoring
OH + unsaturated ester / products
OH + ref / products
(8)
(9)
of reactants and products in the IR spectral range 4000–
ꢂ1
7
00 cm . The mirror system was operated with 82 infrared
Provided that the reference compound and the reactant are
light traverses resulting in a total optical path length of 484.7 ꢀ lost only by reactions (8) and (9), then it can be shown that:
0
1
.8 m. The IR spectra were recorded with a spectral resolution of
cm using a Nicolet Nexus FT-IR spectrometer, equipped
ꢀ½
ꢁ
ꢀ
ꢁ
unsaturated esterꢄ
kunsaturated ester
½refꢄ
ꢂ1
t0
t0
ln
¼
ln
(10)
½
unsaturated esterꢄ
k
ref
½refꢄt
t
with a liquid nitrogen cooled mercury–cadmium–telluride
(MCT) detector. The reactor temperature was adjustable to where [unsaturated ester] , [ref] , [unsaturated ester] and [ref]
t t t t
0 0
a precision of ꢀ1 K in the range 283 to 314 K.
are the concentrations of the unsaturated ester and reference
In the investigations 15 spectra were recorded per experi- compound at times t ¼ 0 and t, respectively, and kunsaturated ester
ment, whereby 64 interferograms were co-added per spectrum and kref are the rate coefficients of reactions (8) and (9),
over 1 min, and the rst ve spectra were recorded in the respectively.
absence of light. Hydroxyl radicals (OH) were generated in situ
Eqn (10) is only valid when the ester and the reference are
by photolysis of methyl nitrite (CH ONO) in the presence of NO/ removed solely by reaction with OH radicals. To verify this
3
O :
2
assumption, various tests were performed to ascertain whether or
not photolysis, wall loss and reaction of the unsaturated esters
and reference compounds with methyl nitrite/NO were negligible.
hn
ONO ƒ ƒƒ ! CH
CH
3
3
O þ NO
(5)
53724 | RSC Adv., 2016, 6, 53723–53729
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The tests showed that all of these loss processes were negligible
over the time period of the experiments, i.e. photolysis of the ester
and reference compounds in the absence of the OH source was
negligible and no signicant wall loss of either the ester or
reference compound was observed on leaving the compounds to
stand in the dark in the reactor in the presence of the OH radical
precursor. The IR spectra for the unsaturated esters alone and for
the mixture before photolysis and during the kinetic experiments
are provided now in the ESI le (Fig. S1 to S12†).
Temperature dependencies of the ester OH radical rate
coefficients
Examples of the kinetic data obtained in the temperature range
2
88–314 K for the reactions of OH radicals with methyl croto-
nate, methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-
-butenoate relative to that of OH 1-butene kinetic are shown
3
plotted according to eqn (10) in Fig. 1–4. The plots show
reasonable linear correlations with near zero intercepts for all
the esters at the three temperatures shown. Similar good linear Fig. 2 Plot of the kinetic data for the reaction of OH radicals with
methyl-3,3-dimethyl acrylate obtained at 289, 302 and 313 K, using 1-
butene as reference hydrocarbon.
correlations were also obtained for the other two temperatures
investigated; these have been omitted from the plots for clarity.
Table 1 lists the rate coefficient ratios obtained at each of the

ve temperatures investigated from linear least-squares anal-
yses of the kinetic data plots and the absolute rate coefficients
obtained with OH for each unsaturated ester derived from the
rate ratios. Table 1 also lists the Arrhenius parameters obtained
from linear ts to plots of ln k versus 1/T for each ester as shown
in Fig. 5. The rate coefficient ratios listed in Table 1 are the
average values obtained from at least 2–3 experiments per
compound and per temperature. The rate coefficients for the
reactions of OH radicals with the unsaturated esters were
placed on an absolute basis using rate coefficients for the
reaction of OH with 1-butene calculated for the respective
3
temperatures from the Arrhenius expression (in cm per mole-
ꢂ12
3
cule per s units): k(OH+1-butene) ¼ 6.55 ꢁ 10
exp(4.67/T) cm
12
per molecule per s.
Fig. 3 Plot of the kinetic data for the reaction of OH radicals with (E)-
ethyl tiglate obtained at 288, 302 and 314 K, using 1-butene as refer-
ence hydrocarbon.
The errors quoted for the rate coefficients given in Table 1
are a combination of 2s statistical errors from the linear t
analyses of the plots and an additional 20% error allocated
to potential errors in the recommended value of the rate
coefficient for the reference reaction. The errors for the ratios
kunsaturated ester/kref are only 2s statistical errors.
For the four unsaturated esters studied MC, MDMA, ET and
M3B the reaction rate coefficients were found to decrease
slightly with increasing temperature over the range of temper-
ature investigated. The Arrhenius expressions presented below
describe reasonably well the OH-radical kinetic temperature
Fig. 1 Plot of the kinetic data for the reaction of OH radicals with dependence of the esters in the temperature range 288–314 K
3
methyl crotonate obtained at 288, 291 and 311 K, using 1-butene as
with k in units of cm per molecule per s:
reference hydrocarbon.
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Fig. 5 Arrhenius plots of the kinetic data obtained in this study
between 288 and 314 K for the reactions of OH radicals with methyl
crotonate (O); methyl-3,3-dimethyl acrylate (,); (E)-ethyl tiglate (B)
and methyl-3-butenoate (>). The filled symbols correspond to
previous measurements from our group for the title reactions at
Fig. 4 Plot of the kinetic data for the reaction of OH radicals with
methyl-3-butenoate obtained at 289, 301 and 313 K, using 1-butene as
reference hydrocarbon.
8,9
298 K.
k1(OH+MC) ¼ (3.39 ꢀ 0.78) ꢁ 10ꢂ12 exp[(750 ꢀ 159)/T]
k
2(OH+MDMA) ¼ (2.95 ꢀ 0.63) ꢁ 10ꢂ11 exp[(838 ꢀ 182)/T]
The weak negative temperature behavior illustrated by the
3(OH+ET) ¼ (1.49 ꢀ 0.56) ꢁ 10ꢂ11 exp[(522 ꢀ 114)/T]
Arrhenius analysis can be attributed to the existence of a stable
van der Waals pre-reactive complex in the entrance of the
reaction channel which explains satisfactorily the observed
temperature dependence of the reactions of OH with the
k
k4(OH+M3B) ¼ (1.90 ꢀ 1.25) ꢁ 10ꢂ12 exp[(834 ꢀ 185)/T]
13
unsaturated esters. This is the generally accepted mechanism
12,14,15
The errors in the activation term and the pre-exponential for OH-radical addition to alkenes
and for unsaturated
factor are the 2s random statistical errors from ts to the data VOCs in general. The weak negative activation energies found
presented in Table 1 and plotted in Fig. 5.
for reactions (1) to (4) are also in agreement with ndings from
16
a
Table 1 Rate coefficients ratios, kunsaturated ester/kref, rate coefficients, kunsaturated ester, and Arrhenius parameters, E /R and A, for the gas-phase
reactions of OH radicals with methyl crotonate, methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate determined at different
temperatures
ꢂ11
ꢂ12
k
unsaturated
k
unsaturated ester ꢁ 10
A/103
3
T (K)
ester/kref
(cm per molecule per s)
Reactant
ꢂE
a
/R (K)
(cm per molecule per s)
288
291
305
308
311
289
291
302
308
313
288
291
302
308
314
289
291
301
308
313
1.37 ꢀ 0.01
1.41 ꢀ 0.02
1.21 ꢀ 0.03
1.35 ꢀ 0.03
1.32 ꢀ 0.02
1.69 ꢀ 0.03
1.53 ꢀ 0.02
1.54 ꢀ 0.02
1.55 ꢀ 0.02
1.44 ꢀ 0.03
2.78 ꢀ 0.05
2.62 ꢀ 0.04
2.85 ꢀ 0.05
2.66 ꢀ 0.07
2.66 ꢀ 0.04
1.05 ꢀ 0.02
1.05 ꢀ 0.02
0.86 ꢀ 0.01
1.03 ꢀ 0.02
0.93 ꢀ 0.01
4.55 ꢀ 0.96
4.61 ꢀ 0.98
3.68 ꢀ 0.82
4.03 ꢀ 0.90
3.87 ꢀ 0.84
5.58 ꢀ 1.21
5.00 ꢀ 1.06
4.74 ꢀ 1.01
4.63 ꢀ 0.99
4.20 ꢀ 0.93
9.23 ꢀ 1.31
8.55 ꢀ 1.24
8.78 ꢀ 1.21
7.93 ꢀ 1.12
7.73 ꢀ 1.10
3.47 ꢀ 0.77
3.41 ꢀ 0.74
2.67 ꢀ 0.55
3.06 ꢀ 0.68
2.73 ꢀ 0.59
Methyl crotonate
750 ꢀ 159
838 ꢀ 182
522 ꢀ 114
834 ꢀ 185
3.39 ꢀ 0.78
Methyl-3,3-dimethyl acrylate
(E)-Ethyl tiglate
2.95 ꢀ 0.63
0.149 ꢀ 0.06
1.90 ꢀ 1.25
Methyl-3-butenoate
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our studies on the reactions of OH radicals with other unsatu- Tropospheric OH radical reaction loss rates for the
rated esters, i.e. methyl methacrylate (E /R ¼ 921 K), butyl unsaturated esters
a
methacrylate (E /R ¼ 413 K), butyl acrylate (E /R ¼ 1117 K) and
a
a
The temperature dependencies of the OH-rate coefficients re-
ported in this work were used to calculate the troposphere rate
of loss of the unsaturated esters with respect to reaction with
OH radicals as a function of altitude. At a given temperature (T)
corresponding to a given altitude in the troposphere, the rate of
loss of the unsaturated esters is dened as the product between
17
vinyl acetate (E /R ¼ 540 K).
a
Comparison with previous kinetics determinations at room
temperature
Although, there are no prior experimental determinations of the the OH rate coefficient (T) and [OH] at this altitude.
Arrhenius parameters for the reactions studied, the room
Using a 12 h daytime average global tropospheric OH radical
1
8
6
3
temperature rate coefficients for the reactions of OH radicals concentration of [OH] ¼ 2 ꢁ 10 molecule per cm , the
with methyl crotonate, methyl-3,3-dimethyl acrylate, (E)-ethyl Arrhenius parameters reported in this work and considering
ꢂ1 19
tiglate and methyl-3-butenoate at 298 K were previously re- a lapse rate in the troposphere of ꢂ6.5 K km
,
we have
8,9
ported by our group.
calculated the temperature proles between 0 and 10 km.
8
Teruel et al. reported a rate coefficient of (4.65 ꢀ 0.65) ꢁ Table 2 shows the OH removal rates for the esters studied as
ꢂ11
3
10
cm per molecule per s for the reaction of OH with methyl a function of altitude in the troposphere assuming a tempera-
crotonate at 298 K and 750 Torr total pressure measured using ture of 298.15 K at 0 km. The results shown in Table 2 are
the relative kinetic method and gas chromatography/ame plotted in Fig. 6.
ꢂ1
ionization detection (RR-GC/FID) for the analyses. This value
The loss rates (in s ) of the esters at sea level (0 km) are
is in very good agreement with the values of (4.61 ꢀ 0.98) ꢁ 6.24 ꢁ 10ꢂ5, 8.38 ꢁ 10ꢂ5, 9.80 ꢁ 10 and 1.72 ꢁ 10 and near
ꢂ5
ꢂ4
ꢂ11
3
ꢂ11
3
10
cm per molecule per s and (3.68 ꢀ 0.82) ꢁ 10
cm per
molecule per s reported in this work for the reaction at 291 and
3
05 K, respectively.
On the other hand, Colomer et al. have performed relative
9
kinetic determinations of the reactions of OH with methyl-3,3-
dimethyl acrylate, (E)-ethyl tiglate and methyl-3-butenoate
using FTIR at 298 K and 760 Torr of synthetic air. They re-
3
ported rate coefficients (in cm per molecule per s) of (4.46 ꢀ
ꢂ11
ꢂ11
ꢂ11
1
.05) ꢁ 10 , (8.32 ꢀ 1.93) ꢁ 10
and (3.16 ꢀ 0.57) ꢁ 10
for the reactions of MDMA, ET and M3B, respectively. The
values of k at 298 K are also in agreement with the rate coeffi-
ꢂ11
3
cient values (in units of 10
cm per molecule per s) reported
in this work at temperatures just below and above 298 K (see
Table 1); (5.00 ꢀ 1.06 and 4.74 ꢀ 1.01) for MDMA; (8.55 ꢀ 1.24
and 8.78 ꢀ 1.21) for ET and (3.41 ꢀ 0.74 and 2.67 ꢀ 0.55) for
M3B.
Our previously reported rate coefficient values obtained at
298 K for the title reactions are represented in Fig. 5 as lled
symbols for comparison with the present results. These values
were not included in the determination of the Arrhenius
parameters for the reactions.
Fig. 6 Hydroxyl radical (OH) reaction loss rates for methyl crotonate
C), methyl-3,3-dimethyl acrylate (;), (E)-ethyl tiglate (-) and
methyl-3-butenoate (:) as a function of altitude (km).
(
Table 2 Removal rates of the unsaturated esters studied as a function of altitude in the troposphere
ꢂ1
ꢂ1
ꢂ1
ꢂ1
Altitude (km)
T (K)
kOH+MC(T)[OH] (s
)
k
OH+MDMA(T)[OH] (s
)
k
OH+ET(T)[OH] (s
)
kOH+M3B(T)[OH] (s
)
ꢂ5
ꢂ5
ꢂ4
ꢂ5
0
1
2
3
4
5
6
7
8
9
298.15
291.65
285.15
278.65
272.15
265.65
259.15
252.65
246.15
239.65
233.15
8.38 ꢁ 10
8.88 ꢁ 10
9.40 ꢁ 10
1.00 ꢁ 10
1.07 ꢁ 10
1.14 ꢁ 10
1.22 ꢁ 10
1.32 ꢁ 10
1.43 ꢁ 10
1.55 ꢁ 10
1.69 ꢁ 10
9.80 ꢁ 10
1.04 ꢁ 10
1.11 ꢁ 10
1.19 ꢁ 10
1.28 ꢁ 10
1.38 ꢁ 10
1.50 ꢁ 10
1.63 ꢁ 10
1.78 ꢁ 10
1.95 ꢁ 10
2.14 ꢁ 10
1.72 ꢁ 10
1.78 ꢁ 10
1.86 ꢁ 10
1.94 ꢁ 10
2.02 ꢁ 10
2.12 ꢁ 10
2.24 ꢁ 10
2.36 ꢁ 10
2.48 ꢁ 10
2.64 ꢁ 10
2.80 ꢁ 10
6.24 ꢁ 10
6.64 ꢁ 10
7.08 ꢁ 10
7.58 ꢁ 10
8.14 ꢁ 10
8.78 ꢁ 10
9.50 ꢁ 10
1.03 ꢁ 10
1.13 ꢁ 10
1.23 ꢁ 10
1.36 ꢁ 10
ꢂ5
ꢂ5
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ4
ꢂ5
ꢂ5
ꢂ5
ꢂ5
ꢂ5
ꢂ5
ꢂ4
ꢂ4
ꢂ4
ꢂ4
1
0
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to the tropopause (ꢃ10 km) around 1.36 ꢁ 10 , 1.69 ꢁ 10
Paper
ꢂ4
ꢂ4
POCP
,
reaction with OH radicals to provide estimated POCPs (3
)
ꢂ4
ꢂ4
2
.14 ꢁ 10 and 2.80 ꢁ 10 for M3B, MC, MDMA and ET, using an analytical expression. This analytical expression gives
POCP
respectively.
The loss rate of ethyl tiglate is the largest and that of methyl- of different compound classes.
-butenoate is the smallest at all altitudes while the other two This estimate method gives values of 3
3
values which are in reasonable agreement for a wide range
POCP
3
for MC, MDMA,
unsaturated esters have intermediate values, as expected taking ET and M3B of around 57, 62, 66 and 57, respectively, indicating
into account the larger and lower rate coefficients kOH(T) for ET that these unsaturated esters will contribute signicantly to the
and M3B, respectively.
formation of tropospheric ozone.
Atmospheric implications
Conclusions
As stated in our previous studies the main tropospheric fate for
methyl crotonate, methyl-3,3-dimethyl acrylate, (E)-ethyl tiglate
and methyl-3-butenoate will be reaction with OH radicals
resulting in lifetimes of 3 hours for methyl crotonate and
Arrhenius expressions for the reactions of OH radicals with the
unsaturated esters MC, MDMA, ET and M3B have been reported
over the temperature range of 288–314 K. For the four unsatu-
rated esters studied the reaction rate coefficients were found to
decrease slightly with increasing temperature over the range of
temperature investigated.
The faint negative temperature dependence observed in the
Arrhenius analysis can be attributed to the existence of a stable
van der Waals pre-reactive complex in the entrance of the
reaction channel which explains satisfactorily the observed
temperature behavior of the reactions of OH with these unsat-
urated esters.
For the four unsaturated ester studied the main degradation
pathway will be reaction with OH radicals. Employing the
Arrhenius expressions obtained in this work, the atmospheric
lifetimes of these unsaturated esters with respect to reaction
with OH were calculated as a function of temperature and also
their variation with altitude between 0 and 10 km. The values
obtained decrease with altitude, reecting the decline of
temperature with altitude and associated decrease in reaction
rates of the reactions.
8,9
methyl-3,3-dimethyl acrylate and 2 and 4 hours for (E)-ethyl
9
tiglate and methyl-3-butenoate, respectively. Using the Arrhe-
nius expressions reported in this work, we have calculated the
atmospheric lifetimes of the unsaturated esters for different
temperatures and their variations with altitude.
With the rate coefficients obtained at different temperatures
for the reactions studied, we have estimated the lifetimes for the
four unsaturated VOCs studied as a function of altitude.
The calculations show that the estimated lifetimes of these
unsaturated esters with respect to reaction with OH decrease
with altitude (from sea level to near the tropopause) by around
50% for methyl crotonate (with lifetimes from 3.30 to 1.64
hours, respectively), 46% for methyl-3,3-dimethyl acrylate (with
lifetimes from 2.83 to 1.30 hours, respectively), and methyl-3-
butenoate (with lifetimes from 4.45 to 2.04 hours, respec-
tively) and 60% for (E)-ethyl tiglate (with lifetimes from 1.61 to
0.99 hours, respectively) reecting the decrease of temperature
with altitude and associated decrease in reaction rates of the
reactions. The temperature dependent rate coefficients deter-
mined in this study will allow a better representation in three- Acknowledgements
dimensional climate models where temperature variations in
reactions are considered.
20
The authors wish to acknowledge the EU project EURO-
CHAMP2, SECYT (Argentina), CONICET (Argentina), ANPCyT-
FONCYT (Argentina), SECyT-UNC (C ´o rdoba, Argentina) for
The OH-radical initiated tropospheric degradation of the
unsaturated esters studied is expected to result mainly in the
formation of oxygenated VOCs such as aldehydes and dicar-
bonyls compounds, which will be subject to further reaction
with OH and also photolysis. The exact identication and yields
of the products formed from the reaction of OH radicals with
the compounds studied here still remain to be investigated. The
high reactivity and thus short atmospheric lifetimes of the
unsaturated esters and also their primary products implies they
will contribute signicantly to formation of ozone and other
photooxidants in the atmosphere close to their emission sour-
ces if emitted in large quantities.

nancial support of this research.
References
1 J. Arey, A. M. Winer, R. Atkinson, S. M. Aschmann,
W. D. Long and C. L. Morrison, Atmos. Environ., 1991, 25,
1063.
2 R. Fall, T. Karl, A. Hansel, A. Jordan and W. Lindinger, J.
Geophys. Res., 1999, 104, 963.
3 T. E. Graedel, Chemical compounds in the atmosphere,
Academic Press, New York, 1978.
The photochemical ozone creation potential (POCP) is
a modelling method used to estimate the ozone creation
potential of VOCs relative to that of ethene which is given the
4 S. Green, A. Goldberg and J. Zurlo, Toxicol. Sci., 2001, 63, 6.
5 http://www.cs3-hq.oecd.org/scripts/hpv/index.asp.
6 S. Srivastava, Des. Monomers Polym., 2009, 12, 1.
7 A. Mellouki, G. L. Bras and H. Sidebottom, Chem. Rev., 2003,
103, 5077.
2
1–24
value 100.
To make POCP values more readily calculable
23
without resource to computer modelling Derwent et al. and
24
Jenkin et al. have developed a simplied estimation procedure
which uses fundamental molecular properties molecular
weight, number of reactive bonds, and rate coefficient for
8 M. A. Teruel, J. Benitez-Villalba, N. Caballero and
M. B. Blanco, J. Phys. Chem. A, 2012, 116, 6127.
53728 | RSC Adv., 2016, 6, 53723–53729
This journal is © The Royal Society of Chemistry 2016

View Article Online
Paper
RSC Advances
9
J. P. Colomer, M. B. Blanco, A. B. Pe n˜ ´e n˜ ory, I. Barnes, 19 M. Beychok, http://www.eoearth.org/view/article/170859,
P. Wiesen and M. A. Teruel, Atmos. Environ., 2013, 79, 546. 2013.
0 I. Barnes, K. H. Becker and N. Mihalopoulos, J. Atmos. Chem., 20 A. Guenther, C. N. Hewitt, D. Erickson, R. Fall, C. Geron,
1
1
1994, 18, 267.
T. Graedel, P. Harley, L. Klinger, M. Lerdau, W. A. McKay,
T. Pierce, B. Scholes, R. Steinbrecher, R. Tallamraju,
J. Taylor and P. Zimmerman, J. Geophys. Res.: Atmos., 1995,
100, 8873.
1 W. D. Taylor, T. D. Allston, M. J. Moscato, G. B. Fazekas,
R. Kozlowski and G. A. Takacs, Int. J. Chem. Kinet., 1980,
12, 231.
1
2 J. G. Calvert, R. Atkinson, J. A. Kerr, S. Madronich, 21 R. G. Derwent, M. E. Jenkin and S. M. Saunders, Atmos.
G. K. Moortgat, T. J. Wallington and G. Yarwood, The Environ., 1996, 30, 181.
mechanisms of atmospheric oxidation of the alkenes, Oxford 22 R. G. Derwent, M. E. Jenkin, S. M. Saunders and M. J. Pilling,
University Press, New York, 2000. Atmos. Environ., 1998, 32, 2429.
3 D. L. Singleton and R. J. Cvetanovic, J. Am. Chem. Soc., 1976, 23 R. G. Derwent, M. E. Jenkin, N. R. Passant and M. J. Pilling,
1
98, 6812.
Atmos. Environ., 2007, 41, 2570.
14 R. Atkinson, J. Phys. Chem. Ref. Data, 1997, 26, 215.
15 R. Atkinson, Atmos. Environ., 2000, 34, 2063.
16 R. Atkinson and J. Arey, Chem. Rev., 2003, 103, 4605.
17 M. B. Blanco, I. Bejan, I. Barnes, P. Wiesen and M. A. Teruel,
J. Phys. Chem. A, 2009, 113, 5958.
24 M. E. Jenkin, Photochemical Ozone and PAN Creation
Potentials: Rationalisation and methods of estimation. AEA
Technology
plc,
Report
AEAT-4182/20150/003,
AEA
Technology plc., National Environmental Technology
Centre, Culham, Oxfordshire OX14 3DB, UK, 1998.
18 R. Hein, P. J. Crutzen and M. Heimann, Global Biogeochem.
Cycles, 1997, 11, 43.
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 53723–53729 | 53729