Photolysis of n-Propyl Formate in the Presence of O2 and NO2: Peroxy Formyl Propyl Nitrate CH3CH2CH2OC(O)OONO2 Synthesis and Characterization

Article abstract of DOI:10.1021/acs.jpca.5b11313

The photo-oxidation of n-propyl formate (initiated by chlorine atoms) was studied in the presence of NO₂, and the products were identified. The Cl atom attack to the molecule occurs in four sites, leading to the formation of formic acid, carbon dioxide, dicarbonylic products, nitrates, peroxy propionyl nitrate (CH₃CH₂C(O)OONO₂, PPN), and a new peroxynitrate, peroxy formyl propyl nitrate (CH₃CH₂CH₂OC(O)OONO₂, PFPN). To characterize bulk quantities of the PFPN, its synthesis was carried out by the photolysis of mixtures of CH₃CH₂CH₂OC(O)H, NO₂, Cl₂, and O₂. After purification, its infrared spectrum and thermal stability were determined. The main infrared absorption bands and their corresponding cross sections are 796, 1219, 1302, 1741, and 1831 cm^-1 (1.16, 3.11, 0.88, 2.42, and 1.34 × 10^-18 cm² molec^-1, respectively). Thermal decomposition was studied as a function of pressure from 6.0 to 1000 mbar at 298 K, and the activation energy was determined between 293 and 304 K at total pressures of 9.0 and 1000 mbar (E_a = 98 ± 3 and 110 ± 2 kJ/mol, respectively). The atmospheric thermal lifetimes were obtained from kinetic parameters.

Full text of DOI:10.1021/acs.jpca.5b11313

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Article
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Photolysis of n-propyl Formate in the Presence of O and NO. Peroxy Formyl
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Propyl Nitrate CHCHCHOC(O)OONO, Synthesis and Characterization
Jesús Alberto Vila, Gustavo Alejandro Argüello, and Fabio Ernesto Malanca
J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.5b11313 • Publication Date (Web): 25 Dec 2015
Downloaded from http://pubs.acs.org on December 28, 2015
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Photolysis of n-propyl Formate in the Presence of O and NO . Peroxy Formyl Propyl
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Nitrate CH CH CH OC(O)OONO , Synthesis and Characterization
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Jesús A. Vila, Gustavo A. Argüello, Fabio E. Malanca*
INFIQC (CONICET) − Departamento de Fisicoquímica − Facultad de Ciencias Químicas –
Universidad Nacional de Córdoba – Pabellón Argentina Ala 1 – 2° Piso − X5000HUA Ciudad
Universitaria – Córdoba − Argentina
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Abstract:
The photo-oxidation of n-propyl formate (initiated by chlorine atoms) was studied
in the presence of NO and the products were identified. The Cl atom attack to the
2
molecule occurs in four sites leading to the formation of formic acid, carbon dioxide,
dicarbonylic products, nitrates, peroxy propionyl nitrate (CH CH C(O)OONO , PPN), and a
3
2
2
new peroxynitrate, peroxy formyl propyl nitrate (CH CH CH OC(O)OONO , PFPN). In order
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2
2
2
to characterize bulk quantities of the PFPN, its synthesis was carried out by the photolysis
of mixtures of CH CH CH OC(O)H, NO , Cl , and O . After purification, its infrared
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spectrum and thermal stability were determined. The main infrared absorption bands and
-
1
their corresponding cross-sections are: 796, 1219, 1302, 1741, and 1831 cm (1.16, 3.11,
1
8
2
-1
0
.88, 2.42, and 1.34 x 10 cm molec , respectively). Thermal decomposition was studied
as a function of pressure from 6.0 to 1000 mbar at 298 K and the activation energy was
determined between 293 and 304 K at total pressures of 9.0 and 1000 mbar (E = 98 ± 3
a
and 110 ± 2 kJ/mol, respectively). The atmospheric thermal lifetimes were obtained from
kinetic parameters.
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Keywords: Peroxynitrate. Atmospheric degradation. Propyl formate. Thermal stability.
Peroxy Formyl Propyl Nitrate.
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*Corresponding author: Fabio E. Malanca
INFIQC (CONICET)
Departamento de Fisicoquímica
Facultad de Ciencias Químicas
Universidad Nacional de Córdoba
fmalanca@fcq.unc.edu.ar
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Introduction
Esters are important volatile organic compounds. They are used as industrial solvents, as
reagents during the manufacture of perfumes and food flavoring, and as fumigant of stored
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-4
foodstuffs due to its pesticide properties . They are also emitted naturally to the atmosphere
by vegetation and could be formed in the atmospheric degradation of alcohols, ethers, and new
5
biofuels. Propyl formate (CH CH CH OC(O)H) is emitted from some fruits and is formed as a
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degradation product from the family of glycol ethers used in many domestic and industrial
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products. Though there are not reliable estimates of the total atmospheric burden of either the
formate or the peroxynitrate itself, the latter should be considered as a potential source of
pollution, and therefore, the study and understanding of its chemistry is highly needed.
•
Kinetic studies of reactions of formates with OH radicals or chlorine atoms, as well as
determinations of the photo-oxidation mechanisms in the presence and absence of nitrogen
dioxide have been performed by several authors who aimed to predict the possible impact of
their emissions to the atmosphere. The rate coefficient for methyl, ethyl, n-propyl and n-butyl
•
-13
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-12
-12
3
formates with OH radicals at 298 K (1.80 × 10 , 8.43 × 10 , 1.82 × 10 , 3.82 × 10 cm
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-1
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molec s respectively) show that these species can react in the troposphere, with the
concomitant formation of degradation products. On the other hand, the rate coefficient of
7-11
these formates with chlorine atoms has been determined by several authors.
The rate
-
11
3
-1 -1 8,10
coefficient for n-propyl formate at 298 K ranges from 4.3 to 5.6 x 10 cm molec s .
The reaction mechanism initiated by chlorine atoms in the presence and absence of NO2,
as well as the branching ratio for the attack of chlorine atoms to the different hydrogen atoms
of the molecule were determined for methyl- and ethyl formates by Wallington et al. (2001),
1
,12-14
Hansen et al. (2002), Malanca et al. (2009) and Orlando et al. (2010), respectively.
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Many studies have concluded that the oxidation of either hydrogenated or fluorinated
compounds in the presence of NO leads to the formation of peroxynitrates (ROONO ),
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15-18
important reservoir species in the atmosphere.
In particular, the photo-oxidation of
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formates in the presence of NO should lead to the formation of an important family of
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thermally stable peroxy acyl nitrates, CxH2x+1OC(O)OONO , of which only the shorter chain
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1
,18
(x=1,2) congeners have been reported.
In this work, we have studied the oxidation of n-propyl formate in the presence of NO2,
determined its reaction mechanism, quantified the main products formed, and characterized
the new peroxynitrate (identified as peroxy formyl propyl nitrate CH CH CH OC(O)OONO PFPN)
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2
2
as well as determined some of its physicochemical properties.
Experimental
Materials
Commercially available samples of propyl formate (Sigma Aldrich), NO (AGA) and O2
AGA) were used. NO was synthetized by the thermal decomposition of Pb(NO ) . Cl was
(
2
3 2
2
prepared by the reaction between HCl and KMnO , and was then distilled.
4
Procedure
Gases were manipulated in a glass vacuum line equipped with two capacitance pressure
gauges (0 – 760 Torr, MKS Baratron; 0 – 70 mbar, Bell and Howell).
Photolyses of mixtures of CH CH CH OC(O)H (3.0 mbar)/ Cl (1.5 mbar)/ NO (0 or 0.7
3
2
2
2
2
mbar)/ O (1000 mbar) were carried out in an IR gas cell (optical path 23.0 cm; silicon windows),
2
using two black lamps, following the temporal variation of reactant and products through IR
-1
-1
spectroscopy. Spectra were acquired in the range 4000 - 400 cm with a resolution of 2 cm
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using a FTIR spectrophotometer BRUKER IR IFS28. This set-up was also used to quantify the
products formed.
Additionally, to identify the products formed in the photo-oxidation in the absence of
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NO , samples were photolyzed in a 5 L glass flask. The resulting mixture was transferred to a set
2
of three cold traps where its components were distilled using baths at different temperatures (-
100, -70 and -50ºC). The resulting fractions were transferred to the infrared gas cell and their
spectra were analyzed.
In order to characterize the PFPN, it was synthesized and further purified. The syntheses
were carried out in a photo-reactor maintained at low temperature (0 to 3 °C) to avoid its
thermal decomposition. The progress of the reaction was checked every 30 min. by taking small
samples from the reactor and recording the infrared spectra. The photolysis was stopped when
50% of the reactant had disappeared. The resultant mixture was collected by slowly passing it
through three traps kept in liquid N in order to remove excess O , and non-condensable
2
2
products. The distillation from -80 ºC to -120 ºC led to the elimination of ClNO and CO , and
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successive distillations from -50ºC to -100ºC allowed the removal of propyl formate, nitrates,
and most of the formic acid. The remnant fraction contained mainly PFPN and a small amount
(<2%) of formic acid.
Thermal stability of PFPN was determined between 293 and 304 K using a proven
1
5,18
methodology frequently employed,
that adds NO (1.0 mbar) to the reaction vessel in order
to capture the peroxy radicals formed in the decomposition. The temporal variation of the
peroxynitrate concentration for 0.4 mbar samples of PFPN was monitored by infrared
-
1
spectroscopy using the bands at 796 and 1742 cm . The results were analyzed according to a
first-order rate law at each temperature and thus an Arrhenius plot was obtained.
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Theoretical calculations to give the infrared spectrum were performed with the Gaussian
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03 program suite. Geometric optimizations, and calculations of the vibrational frequencies of
PFPN were carried out by applying Density Functional Theory (DFT) methods, using the B3LYP
exchange functional with 6-311++ G(d,p) basis.
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Gas chromatography/mass spectrometry (GC/MS) analyses were performed in a
Shimadzu GC-MS-QP 5050 spectrometer equipped with a capillary column Zebron 2B-5MS (30
m × 0.25 mm × 0.25 ꢀm) using helium as eluent at a flow rate of 1.1 mL / min. Both injector and
ion source temperatures were 280ºC, the oven heating ramp was 15 ºC / min. from 25 ºC up to
-5
2
80 ºC. The pressure in the MS instrument was 10 torr, precluding ion-molecule reactions from
taking place, and MS recording were made in the electron impact (EI) mode with ionization
energy of 70 eV.
Results and discussions
Photo-oxidation of CH CH CH OC(O)H in the presence of NO
2
3
2
2
Figure 1 shows the sequence of infrared spectra obtained in the photolysis of
CH CH CH OC(O)H, Cl , NO , and O mixtures. The first and second traces correspond to t=0 and
3
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2
2
2
2
t=60 min. of irradiation, respectively. The third trace (A), obtained from the subtraction of
reactants to the second one, shows the products formed. It is clear that formic acid is formed
-
1
(
peaks at 1105 and 1775 cm ). In the fourth trace (B), formic acid has been subtracted and the
-
1
spectrum shows two peaks characteristic of peroxynitrates (796 and 1742 cm ). The fifth trace
C) shows the reference spectrum of PFPN, obtained as will be explained in a subsequent
section. Its subtraction from the fourth trace (paying special attention to the band centered at
(
-1
1
219 cm that we independently know that belongs to PFPN) leads to the sixth trace (D) and
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reveals still another peroxynitrate formed in the photolysis. The next (seventh) trace shows the
reference spectra of peroxy propionyl nitrate (PPN), whose subtraction from the sixth trace
leads to the last one, in which circles highlight the formation of nitrates (bands at 1650, 1280,
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and 850 cm ) and asterisks point to the formation of other carbonylic compounds (bands at
-1
1
758 and 1166 cm ). Carbon dioxide is also formed in the photolysis (though it is not shown in
the Figure).
t = 0 min
t = 60 min
A
B
C
D
E
*
*
F
2
000
1600
1200
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-
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ν (cm )
FIGURE 1
Information about the identity of the carbonyl products was obtained from similar
experiments carried out in the absence of nitrogen dioxide. Figure 2 shows the spectrum of
products obtained in the photolysis of CH CH CH OC(O)H, Cl and O mixtures after 60 minutes
3
2
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2,
2
of irradiation (first trace). The subtraction of a reference spectrum of formic acid to this first
trace leads to a new one that shows the presence of the same carbonylic signals as those of
trace F of Figure 1, though their intensities are higher in the absence of NO . This could be
2
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explained by taking into account that the photolysis in the presence of nitrogen dioxide leads to
the formation of both nitrate and peroxynitrate and, consequently, the formation of carbonylic
products is decreased.
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ν
(cm )
FIGURE 2
Identification of these carbonylic compounds required photolysis of bulk quantities in
the absence of NO and appropriate fractionation using cold baths. The most abundant products
2
identified by FTIR were carbon dioxide and formic acid, while the less volatile fraction shows
other carbonylic compounds that needed to be analyzed by gas chromatography coupled to
mass spectrometry. A typical chromatogram shows three peaks at retention times ranging from
3 to 4 minutes. Based on their fragmentation patterns, we are led to conclude that the species
+
+
+
+
are CH C(O)CH OC(O)H (m/e: 15, CH ; 43, CH CO ; 59, C H O ; 87, M- CH ; 101, M ),
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+
+
+
+
+
+
CH CH C(O)OC(O)H (m/e: 27, C H ; 29, C H , CHO ; 45, CO H ; 59, C H O ; 74, C H O ; 87, M-
3
2
2
3
2
5
2
3
7
3 6 2
+
+
+
+
+
CH ; 101 M ) and HC(O)CH CH OC(O)H (29, CHO ; 44, CO ; 58, C H O ; 73, C H O ), all of them
3
2
2
2
3
6
3 5 2
formed from the reaction of oxy radicals with molecular oxygen, as will be discussed.
The explanation of the products observed (in the presence and absence of nitrogen
dioxide) could be as follows; chlorine atoms attack n-propyl formate at four different sites
forming the respective radicals (Reaction 1a-d)
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•
•
CH CH CH OC(O)H + Cl
→
→
→
→
CH CH CH OC(O)H + HCl
1a
1b
1c
1d
3
2
2
2
2
2
•
CH CH CH OC(O)H + HCl
3
2
•
CH CH CH OC(O)H + HCl
3
2
•
CH CH CH OC(O) + HCl
3
2
2
In the presence of O , all these radicals lead to the formation of peroxy radicals:
2
•
•
•
OOCH CH CH OC(O)H,
CH CH(OO )CH OC(O)H,
CH CH CH(OO )OC(O)H,
and
2
2
2
3
2
3
2
•
CH CH CH OC(O)OO . From these radicals, the only one that could lead directly to a stable
3
2
2
peroxynitrate in the presence of nitrogen dioxide is the last one, which gives
•
CH CH CH OC(O)OONO . The other peroxy radicals form the oxy radicals OCH CH CH OC(O)H
3
2
2
2
2
2
2
•
•
(
R1), CH CH(O )CH OC(O)H (R2), and CH CH CH(O )OC(O)H (R3) after interaction with either
3 2 3 2
chlorine atoms or nitrogen monoxide formed from the photolysis of NO . These C4 alkoxy
2
radicals still have some reaction paths available: either reaction with O to form dicarbonylic
2
compounds; breaking of C-C or C-O bonds to form shorter chain compounds; α-ester
rearrangement to form acids; or isomerization via a 1,5-H atom shift that preserves the length
20
of the carbon chain.
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As might be expected by analogy to non-substituted radicals of similar structure,
reaction with O is a major fate for R1 to form 3-oxopropyl formate (HC(O)CH CH OC(O)H),
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20,21
while decomposition via C-C bond cleavage appears to dominate for R2.
The rearrangement
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process could, a priori, be the major fate for R3, on account of its analogy with the
•
CH CH(O )OC(O)CH radical, though reactions with O , decomposition via C-C or C-O bond
3
3
2
scission, or isomerization may also occur to a smaller degree as pointed out by Piquet et al and
21,22
Tuazon et al.
Nevertheless, R2 and R3 could still lead to minor quantities of
CH C(O)CH OC(O)H and CH CH C(O)OC(O)H because of the reaction with O . In the presence of
3
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2
2
nitrogen dioxide, an additional path to form nitrates opens.
Scheme 1 shows the reaction mechanism in the presence of NO . The reactions following
2
•
the formation of CH CH CH OC(O)OO lead to PFPN (CH CH CH OC(O)OONO ). Further
3
2
2
3
2
2
2
•
decomposition of PFPN could lead to CO and CH CH CH O radicals that, in the presence of
2
3
2
2
nitrogen dioxide, mainly end in n-propyl nitrate formation. As can be seen from the yields
presented in the Scheme, the formation of PFPN accounts for about 10% of the disappearance
of the formate.
On the other hand, R3 leads to the formation of formic acid, PPN (15 %), carbon dioxide,
CH CH C(O)OC(O)H, and ethyl nitrate, all of them identified by infrared or mass spectroscopy.
3
2
The radical R2, leads to the formation of CH C(O)CH OC(O)H and formic acid. Finally, the radical
3
2
R1 leads to the formation of HC(O)CH CH OC(O)H. As expected, the quantities of formic acid
2
2
formed (25 %) are not modified by the addition of NO , considering that its formation occurs
2
through a α-ester rearrangement. The quantification of total nitrates formed in the photolysis
with NO explains about (26 ± 3) of the disappearance of the precursor formate.
2
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O
O
O
O
1
2
O2
O2
O
O
O
O
O
O
O
O
O
Cl, NO, RO2
Cl, NO, RO2
O
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+
O
O
O
O
O
O
O
O
O
O2
O2
O2
O
O
O
O
O
O
O
O
Cl, NO, RO2
O
O
HO
O
+
HC(O)
O2
O
O2
O
O
CO
O
O
O
3
O
O2
O
O
O
Cl, NO, RO2
O
O
HO
O
+
O2
O
O
O2
O
O
NO
2
O
O
O
O N
2
O
O
O
O
PPN 15 %
CH CH
+ CO
2
2
Cl, NO, RO2
O
3
O2
O
Cl, NO, RO2
O
O
4
O
O
O2
NO2
NO2
O
O
NO2
O
O
O
- NO2
O
O
O
Cl, NO, RO2
NO2
O
O
PFPN 10 %
O
NO2
O
O
NO2
CO +
2
SCHEME 1
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2
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5
5
6
Infrared spectrum of PFPN
Figure 3 shows the experimental and calculated spectra of PFPN as well as the infrared
absorption cross-sections. There is a good concordance between both spectra. This feature
could also be used as a confirmation corroborating the identity of PFPN. The calculated
spectrum was obtained from the most stable conformer syn-syn (Figure 4), derived by structure
optimization (see below). The calculation of the vibrational frequencies of possible conformers
of PFPN were carried out by applying Density Functional Theory (B3LYP) methods with 6-311++
G(d,p) basis sets.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
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9
0
1
2
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0
1
2
3
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9
0
1
2
3
4
5
6
7
8
9
0
3
2
1
0
2000
1600
1200
800
-
1
)
ν
(
cm
FIGURE 3
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C1
C3
C4
O2
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59
60
C2
O1
O4
O3
O6
O5
FIGURE 4
During the optimization process of the possible conformers, some common features,
regardless of the starting structure were observed:
-
The dihedral angle formed by the fragment H(1,2,3)-C1-C2-C3 adopts the configuration “anti”
180°) as well as the other dihedrals formed with the fragments C1-C2-C3-O1 and C2-C3-01-C4.
The dihedral angle formed by the fragment O3-04-N1-O5 adopts the configuration “syn” (close
(
-
2
3
to 0°) similar to other peroxinitrates.
Therefore, setting fixed values for these dihedral angles, the study focused on the
remaining ones, that define the position of the C=O bond with respect to the peroxidic bond O3-
O4. The conformers were named according to the following criteria: (a) the position of the C=O
bond with respect to the OO bond defines the first term, whether syn or anti; and (b) the
position of the CH CH CH O bond with respect to the C=O bond defines the second syn-anti
3
2
2
term. The calculations reveal that the most stable conformer is syn-syn in accordance with
1
8
results obtained for CH CH OC(O)OONO by Bossolasco et al. (2011). Tables S1 and S2 show
3
2
2
the calculated geometric parameters, and Cartesian coordinates. The calculated value for both
1
4, 18, 19, 24
the dihedral (COON) and the OO bond distance agree with literature values
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Thermal decomposition of CH CH CH OC(O)OONO
2
3
2
2
•
PFPN exists in equilibrium with NO and CH CH CH OC(O)OO radicals
2
3
2
2
•
CH CH CH OC(O)OONO
→ CH CH CH OC(O)OO + NO
(2)
3
2
2
2
3
2
2
2
0
1
2
3
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0
1
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0
1
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0
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0
1
2
3
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8
9
0
•
CH CH CH OC(O)OO + NO → CH CH CH OC(O)OONO
(-2)
3
2
2
2
3
2
2
2
In order to measure the rate coefficient for the thermal decomposition, the presence of
a radical scavenger is needed. Nitrogen monoxide was added since it efficiently removes the
•
CH CH CH OC(O)OO radicals because of the occurrence of the following reactions (Reactions 3-
3
2
2
6) thus avoiding the regeneration of PFPN (Reaction -2):
•
•
CH CH CH OC(O)OO + NO → CH CH CH OC(O)O + NO
(3)
(4)
(5)
(6)
3
2
2
3
2
2
2
•
•
CH CH CH OC(O)O
→ CH CH CH O + CO
3
2
2
3
2
2
2
•
CH CH CH O + NO
→ CH CH CH ONO
3
2
2
2
3
2
2
2
•
CH CH CH O + NO
→ CH CH CH ONO
3
2
2
3
2
2
The temporal variation of the peroxynitrate concentration was followed by FTIR as was
described previously, and the rate coefficient measured (k ) was corrected using the following
obs
equation,

obs
k
[
NO2
]

−2
k = k 1+


2

[NO
]

k3

which takes into account that, during the thermal decomposition the nitrogen dioxide
concentration increases. The rate coefficient for reactions (-2) and (3) were taken from
literature values corresponding to similar radicals as has been done by many authors (k = 1.12
-
2
-11
-11
3
-1 -1 25, 26
x 10 , k = 2.11 x 10 cm molecule s ).
Nevertheless, this correction accounts for a 6 %
3
of kobs at most. This percentage arises from the use of the reported rate coefficients for reaction
(-2) and (3) as well as the experimental concentration for nitrogen monoxide added to the
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system and the maximum nitrogen dioxide concentration formed as consequence of PFPN
decomposition.
In order to establish the dependence of the rate coefficient of reaction (2) with pressure,
a series of experimental runs were performed at 298 K at different total pressures. The results
presented in Figure 5 show that the dependence is similar to that reported by Bossolasco et al.
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60
1
8
(2011) for peroxy ethoxy formyl nitrate (PEFN), though we can not explain why the high
pressure limit has not been reached at 1000 mbar for a molecule possessing a higher number of
degrees of freedom.
2
2
2
.5
.4
.3
-
-
-
-
-
7.2
7.8
8.4
9.0
9.6
2.2
2.1
3.30
3.35
3.40
3
-1
/T x 10 (K )
1
0
300
600
900
1200
P (mbar)
FIGURE 5
The kinetic parameters (E , activation energy, A, pre-exponential factor) derived from
a
the Figure give the following values at 9.0 and 1000 mbar: E = (98 ± 3) kJ/mol and Ln A = (31 ±
a
1
); E = (110 ± 2) kJ/mol, and Ln A = (36.1 ± 0.8), respectively. The comparison of the values of Ea
a
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2
2
2
2
2
2
2
2
3
3
3
3
3
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determined at 1000 mbar with those reported for CH OC(O)OONO (107 ± 5) kJ/mol and
3
2
1
8
C H OC(O)OONO (108 ± 5) kJ/mol shows good agreement for the family C H2x+1OC(O)OONO2.
2
5
2
x
The closeness of the values for E , all of them comprised within the experimental errors,
a
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
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9
0
1
2
3
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9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
preclude us to establish a definite trend in the stability of this family as a function of the length
of the carbonated chain.
Conclusions
In this paper, we determined the main products resulting from the photo-oxidation of n-
propyl formate, both in the presence and in the absence of NO , as well as the reaction
2
mechanism. In the atmosphere, emissions of n-propyl formate could contribute to the
formation of nitrates, dicarbonyl compounds, and PFPN.
The comparison of its thermal stability with peroxynitrates of the shorter carbonated
chain CxH2x+1OC(O)OONO (x = 2, 3) leads to conclude that this family could act as reservoir
2
species in the atmosphere. In particular, the lifetime of PFPN at an altitude of 2 Km is about one
day. It rapidly increase up to 7 months at 6 km, reaching values of years near the tropopause.
Acknowledgments
Financial support from SECYT-Universidad Nacional de Córdoba, ANPCyT, and CONICET is
gratefully acknowledged. JAV acknowledges the fellowship he holds from CONICET.
Supporting Information Available
Geometric parameters for the syn-syn PFPN conformer (Table S1) and cartesian matrix
for syn-syn PFPN (Table S2).
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References
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Simmons, P.; Gertler, S. I. Ethyl Formate and Isopropyl Formate as Fumigants for Packages of
Dried Fruits. J. Econ. Entomol. 1945, 38, 715–716.
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Cotton, R. T. Fumigating Stored Foodstuffs, Yearbook of Agriculture 1952, U.S. Government
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Le Calve, S.; Le Bras, G.; Mellouki, A. Temperature Dependence for the Rate Coefficients of the
Reactions of the OH Radical with a Series of Formates J. Phys. Chem. A. 1997, 101, 5489–5493.
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Notario, A.; Le Bras, G.; Mellouki, A. Absolute Rate Constants for the Reactions of Cl Atoms
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Good, D. A.; Hansen, J.; Kamoboures, M.; Santiono, R.; Francisco, J. S. An Experimental and
Computational Study of the Kinetics and Mechanism of the Reaction of Methyl Formate with Cl
Atoms. J. Phys. Chem. A. 2000, 104, 1505-1511.
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0
Wallington, T. J.; Hurley, M. D.; Haryanto, A. Kinetics of the Gas Phase Reactions of Chlorine
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Bravo, I.; Aranda, A.; Díaz-de-Mera, Y.; Moreno, E.; Tucceri, M. E.; Rodríguez, D. Kinetics,
Mechanistic and Temperature Dependence Study of the Cl Reactions with CH OC(O)H and
3
CH CH OC(O)H: Atmospheric Implications, Phys. Chem. Chem. Phys. 2009, 11, 384-390.
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2
Hansen, J. C.; Francisco, J. S.; Szente, J. J.; Maricq, M. M. An Experimental Study of the
Mechanism and Branching Ratio for the Reaction Between Methyl Formate and Chlorine Atoms.
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Malanca, F. E.; Fraire, J. C.; Argüello, G. A. Kinetics and Reaction Mechanism in the Oxidation
of Ethyl Formate in the Presence of NO . Atmospheric implications. J. Photochem. Photobiol. A.
2
2
009, 204, 75–81.
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4
Orlando J. J.; Tyndall, G. S. The Atmospheric Oxidation of Ethyl Formate and Ethyl Acetate over
a Range of Temperatures and Oxygen Partial Pressures. Int. J. Chem. Kinet. 2010, 42, 397–413.
1
5
Kirchner, F.; Thuner, L. P.; Barnes, I; Becker, K. H.; Donner, B.; Zabel, F. Thermal Lifetimes of
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von Ahsen, S; García, P.; Willner, H.; Argüello, G. A. Trifluoromethoxycarbonyl Peroxynitrate,
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2
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Manetti, M. D; Malanca, F. E.; Argüello, G. A. Thermal Decomposition of
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8
Bossolasco, A. G.; Malanca, F. E.; Argüello, G. A. Peroxy ethoxyformyl nitrate,
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the OH-induced Oxidation of two Linear Acetates: Ethyl and n-propyl Acetate Phys. Chem. Chem.
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Tuazon, E. C.; Aschmann, S. M.; Atkinson, R.; Carter, W. P. L. The Reactions of Selected
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•
Structure RCO CO R'. J. Phys. Chem. 1998, 102, 2316–2321.
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4
Badenes, M. P.; Cobos, J. C. Quantum Chemical Study of the Atmospheric C H C(O)OONO
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2
5
(PPN) Molecule and of the C H C(O)OO and C H C(O)O Radicals. Theochem. 2008, 856, 59-70.
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2
5
Froyd, K. D.; Lovejoy, E. R. Direct Measurement of the C H C(O)O + NO Reaction Rate
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5
2
Coefficient Using Chemical Ionization Mass Spectrometry. Int. J. Chem. Kinet. 1999, 31, 221–228.
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6
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Propionaldehyde Under Simulated Atmospheric Conditions. J. Photochem. 1985, 28, 475–489.
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Captions
Figure 1. Photooxidation of n-propyl formate in the presence of NO . Traces from top to
2
bottom: first, before irradiation; second, after 60 min photolysis; “A”, reaction products “B” =
“A”– HC(O)OH; “C” = PFPN reference spectra ( see text below) ; ”D” = “B” – PFPN; “E” = PPN;
0
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0
“
F”= “D”– PPN. Arrows signal the peaks corresponding to formic acid. Circles and asterisks show
the peaks corresponding to remnant nitrates and carbonylic compounds, respectively.
Figure 2. Photooxidation of n-propyl formate in the absence of NO . Traces from top to bottom:
2
“A”, products after 60 min of photolysis; “B” = “A”– HC(O)OH; “C”, trace “F” taken from Figure 1
for comparison.
Figure 3. Absorption cross-sections and calculated spectra of PFPN.
Figure 4. Calculated structure for the most stable conformer (syn – syn conformer).
Figure 5. Thermal decomposition of PFPN as a function of pressure. Errors bars represent one
standard deviation taken from the temporal variation of peroxynitrate at each pressure.
Scheme 1. Mechanism of oxidation in the presence of nitrogen dioxide.
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t = 0 min
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60
t = 60 min
A
B
C
D
E
*
*
F
2
000
1600
1200
800
-
1
ν (cm )
FIGURE 1
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The Journal of Physical Chemistry
Page 22 of 27
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A
B
C
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-1
800
ν
(cm )
FIGURE 2
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3
2
1
0
2000
1600
1200
1)
800
-
ν
(
cm
FIGURE 3
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C1
C3
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C4
O2
C2
O1
O4
O3
O6
O5
Figure 4
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Page 25 of 27
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.5
.4
.3
.2
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-
-
-
-
-
7.2
7.8
8.4
9.0
9.6
2.1
3.30
3.35
3 -1
1/T x 10 (K )
3.40
0
300
600
900
1200
P (mbar)
FIGURE 5
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The Journal of Physical Chemistry
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9
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1
1
1
1
1
1
1
1
1
2
2
2
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2
2
2
2
2
2
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4
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5
5
6
O
O
O
O
1
2
O2
O2
O
O
O
O
O
O
O
O
O
Cl, NO, RO2
Cl, NO, RO2
O
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
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0
1
2
3
4
5
6
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8
9
0
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2
3
4
5
6
7
8
9
0
+
O
O
O
O
O
O
O
O
O
O2
O2
O2
O
O
O
O
O
O
O
O
Cl, NO, RO2
O
O
HO
O
+
HC(O)
O2
O
O2
O
O
CO
O
O
O
3
O
O2
O
O
O
Cl, NO, RO2
O
O
HO
O
+
O
O2
O2
O
O
O
NO
2
O
O
O
O N
2
O
O
O
O
PPN 15 %
Cl, NO, RO2
O
+ CO
2
3
CH CH2
O2
O
Cl, NO, RO2
O
O
4
O
O
O2
NO2
NO2
O
O
NO2
O
O
O
- NO2
O
O
O
Cl, NO, RO2
NO2
O
O
PFPN 10 %
O
NO2
O
O
NO2
CO +
2
SCHEME 1
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