Products of the gas-phase reactions of 1,3-butadiene with OH and NO3 radicals

Article abstract of DOI:10.1021/es990193u

1,3-Butadiene is released into the atmosphere from several sources, e.g., combustion sources, and is listed as a hazardous air pollutant under the CAAA. It reacts with OH radicals, NO₃ radicals, and O₃ in the atmosphere. The products formed from the reactions of 1,3-butadiene with OH radicals (in the presence of NO) and NO₃ radicals were identified and quantified by GC, in situ FTIR absorption spectroscopy, and in situ atmospheric pressure ionization tandem MS (API-MS). Formaldehyde, acrolein, and furan were identified and quantified from the OH radical-initiated reaction, with formation yields of 0.62, 0.58, and 0.03-0.04, respectively. Organic nitrates had an estimated yield of 0.07. API-MS analyses showed that these organic nitrates were mostly the hydroxynitrate HOCH_2- CH=CHCH₂ONO₂ and/or its isomers. API-MS analyses revealed the formation of a hydroxycarbonyl with the C₄H₆O₂ formula, ascribed to HOCH₂CH = CHCHO and/or its isomers. The main products of the NO₃ radical-initiated reaction were organic nitrates. API-MS analyses indicated the formation of 1,2-epoxy-3-butylene, acrolein, and unsaturated C₄-hydroxycarbonyls, carbonyl nitrates, hydroxynitrates, and nitrooxyhydroperoxides. The API-MS and API-MS/MS analyses were consistent with the FTIR data, as well as from those of Barnes et al. (1990) and Skov et al. (1992) showing the formation of acrolein. Detailed reaction mechanisms were discussed.

Full text of DOI:10.1021/es990193u

Environ. Sci. Technol. 1999, 33, 3586-3595
in the troposphere at various locations (3, 13-19). In the
troposphere, 1,3-butadiene can undergo reaction with OH
radicals, NO radicals, O , and Cl atoms (20). By combining
the rate constants for the OH radical, NO radical, and O
reactions with estimated ambient concentrations of these
reactive species, it is calculated that the daytime OH radical
and nighttime NO radical reactions are important trans-
3
formation processes and that 1,3-butadiene typically has a
lifetime in the troposphere of a few hours.
Products of the Gas-Phase
3
3
Reactions of 1,3-Butadiene with OH
3
3
and NO Radicals
3
E R N E S T O C . T U A Z O N ,
†
A L V A R O A L V A R A D O ,
S A R A M . A S C H M A N N ,
However, the products of the gas-phase reactions of 1,3-
butadiene with OH and NO radicals are not fully understood
3
,
‡ , §
R O G E R A T K I N S O N , *
J A N E T A R E Y* , ‡
A N D
(
20-22). The formation of HCHO and acrolein have been
Air Pollution Research Center, University of California,
Riverside, California 92521
observed from the OH radical-initiated reaction of 1,3-
butadiene (23-25) together with furan in 4-6% yield (24,
2
6). However, there is significant disagreement between the
studies of Maldotti et al. (23) and Ohta (24) concerning the
acrolein formation yield, with values of 98 ( 12% and ∼40%,
respectively, being reported for reactions carried out in the
1
,3-Butadiene is emitted into the atmosphere from a
number of sources including combustion sources and is
listed in the United States as a hazardous air pollutant. In
the atmosphere, 1,3-butadiene reacts with OH radicals,
NO3 radicals, and O3 with the dominant tropospheric removal
processes being daytime reaction with the OH radical
and nighttime reaction with the NO3 radical. We have used
gas chromatography, in situ Fourier transform infrared (FT-
IR) absorption spectroscopy, and in situ atmospheric
pressure ionization tandem mass spectrometry (API-MS)
to identify and quantify the products formed from the reactions
of 1,3-butadiene with OH radicals (in the presence of
NO) and NO3 radicals. Acrolein, formaldehyde, and furan
were identified and quantified from the OH radical-initiated
reaction, with formation yields of 0.58 ( 0.04, 0.62 (
presence of NO. For the NO
3
radical reaction, Barnes et al.
(
27) used in situ Fourier transform infrared (FT-IR) spec-
troscopic analyses and reported the formation of HCHO,
acrolein, and organic nitrates with yields of 12%, 12%, and
∼60%, respectively. Skov et al. (28) also used in situ FT-IR
spectroscopy to investigate the reactions of the NO
3
radical
, and 1,3-buta-
radical addition
dominated with the formation of trans-O NOCH CHd
CHCHO and O NOCH C(O)CHdCH as the major products.
with 1,3-butadiene, 1,3-butadiene-1,1,4,4-d
diene-d and concluded that terminal NO
4
6
3
2
2
2
2
2
In this work, we have used gas chromatography, in situ
FT-IR spectroscopy and in situ atmospheric pressure ioniza-
tion tandem mass spectrometry (API-MS) to investigate the
products and mechanisms of the gas-phase reactions of 1,3-
butadiene with OH radicals (in the presence of NO) and NO
radicals. To aid in the identification of products, 1,3-
butadiene-d was also used in experiments employing API-
3
0
.05, and 0.03-0.04, respectively. Organic nitrates were
observed by FT-IR spectroscopy with an estimated yield of
.07 ( 0.03, and the API-MS analyses indicated that
6
0
MS for analyses.
these organic nitrates are mainly the hydroxynitrate HOCH2-
CHdCHCH2ONO2 and/or its isomers. API-MS analyses
showed the formation of a hydroxycarbonyl with the formula
C4H6O2, attributed to HOCH2CHdCHCHO and/or its isomers.
The major products of the NO3 radical-initiated reaction
were organic nitrates; the API-MS analyses indicated the
formation of acrolein, 1,2-epoxy-3-butene, and unsaturated
C4-hydroxycarbonyls, hydroxynitrates, carbonyl nitrates, and
nitrooxyhydroperoxides. Acrolein, HCHO, and furan were
again quantified by gas chromatographic and FT-IR analyses.
Our data are compared with previous literature studies,
and detailed reaction mechanisms are presented and
discussed.
Experimental Methods
Experiments were carried out at 298 ( 2 K and 740 Torr total
pressure of air in a 5870-L evacuable, Teflon-coated chamber
containing an in situ multiple reflection optical system
interfaced to a Nicolet 7199 FT-IR spectrometer and with
irradiation provided by a 24-kW xenon arc filtered through
a 0.25 in. thick Pyrex pane (to remove wavelengths <300
nm); in a 7500-L Teflon chamber with analysis by gas
chromatography with flame ionization detection (GC-FID)
and combined gas chromatography-mass spectrometry
(GC-MS), with irradiation provided by two parallel banks of
black lamps; and in a 7300-L Teflon chamber interfaced to
a PE Sciex API III MS/ MS direct air sampling, atmospheric
pressure ionization tandem mass spectrometer (API-MS),
again with irradiation provided by two parallel banks of black
lamps. All three chambers are fitted with Teflon-coated fans
to ensure rapid mixing of reactants during their introduction
into the chamber.
Introduction
1
2 2
,3-Butadiene [CH dCHCHdCH ] is listed under Title III of
the Clean Air Act Amendments of 1990 as a hazardous air
pollutant (1) and is also on California’s list of toxic air
contaminants (2). 1,3-Butadiene is emitted into the atmo-
sphere from a number of sources including vehicle exhaust
Hydroxyl radicals were generated in the presence of NO
by the photolysis of methyl nitrite or ethyl nitrite in air at
wavelengths >300 nm (29, 30):
(
3-10) and tobacco smoke (3, 11, 12) and has been measured
RCH ONO + hν f RCH O˙ + NO
(1)
(2)
(3)
2
2
*
Corresponding authors.
Present address: U.S. Environmental Protection Agency, Mail
RCH O˙ + O f RCHO + HO
2 2 2
†
Code 3HS41, 1650 Arch Street, Philadelphia, PA 19103.
HO + NO f OH + NO2
2
‡
Also Department of Environmental Sciences, University of
California, Riverside.
§
Also Department of Chemistry, University of California, Riverside.
3
where R ) H or CH . NO was added to the reactant mixtures
3
5 8 6
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 33, NO. 20, 1999
10.1021/es990193u CCC: $18.00

1999 Am erican Chem ical Society
Published on Web 09/03/1999

cm- NO was added to the chamber, and the reactant
3
to suppress the formation of O
3
and hence of NO
3
radicals
(
29). Because HCHO is the major product from the photolysis
mixtures monitored for 60 min. Because 1,3-butadiene reacts
of methyl nitrite in air, HCHO formation yields from the
reaction of the OH radical with 1,3-butadiene were measured
in experiments using ethyl nitrite photolysis as the source of
OH radicals (30).
slowly with NO
carried out to investigate this reaction by FT-IR spectroscopy
2
in the dark (20), an experiment was also
with initial concentrations of NO
2
and 1,3-butadiene of 1.8
1
4
14
-3
× 10 and 2.46 × 10 molecule cm , respectively.
Teflon Cham ber with Analysis by API-MS. In the experi-
ments with API-MS analyses, the chamber contents were
sampled through a 25 mm diameter × 75 cm length Pyrex
NO
tion of N
3
radicals were generated by the thermal decomposi-
in the presence of NO (31, 32):
2
O
5
2
-
1
N O f NO + NO
2
(4)
tube at ∼20 L min directly into the API mass spectrometer
source. The operation of the API-MS in the MS (scanning)
and MS/ MS [with collision activated dissociation (CAD)]
modes has been described elsewhere (35). Use of the MS/
MS mode with CAD allows the “daughter ion” or “parent
ion” spectrum of a given ion peak observed in the MS
scanning mode to be obtained (35). The positive ion mode
2
5
3
Teflon Cham ber Experim ents with GC-FID and GC-
MS Analysis. For the OH radical reactions carried out in the
7
500-L Teflon chamber (at ∼5% relative humidity), OH
radicals were generated by the photolysis of methyl nitrite
in air, and the initial reactant concentrations (in molecule
cm units) were as follows: CH
-
3
14
was used in these API-MS and API-MS/ MS analyses with
protonated water hydrates (H
3
ONO, 2.0 × 10 ; NO, 1.9 ×
+
1
4
13
3
O (H
2
O)
n
) generated by the
1
0 ; and 1,3-butadiene, (5.7-6.2) × 10 . Irradiations were
corona discharge in the chamber diluent gas being respon-
sible for the protonation of analytes. Ions are drawn by an
electric potential from the ion source through the sampling
orifice into the mass-analyzing first or third quadrupole. For
these experiments, the API-MS instrument was operated
under conditions that favored the formation of dimer ions
in the ion source region (35). Neutral molecules and particles
are prevented from entering the orifice by a flow of high-
purity nitrogen (curtain gas), and as a result of the declustering
action of the curtain gas on the hydrated ions, the ions that
are mass-analyzed are mainly protonated molecular ions
carried out at 20% of the maximum light intensity for 2-7
min, resulting in up to 53% reaction of the initial 1,3-
butadiene. The concentrations of 1,3-butadiene and selected
products were measured during the experiments by GC-FID.
The concentrations of 1,3-butadiene were measured as
described previously (33). For the analyses of reaction
3
products, gas samples of 100 cm volume were collected from
the chamber onto Tenax-TA solid adsorbent with subsequent
thermal desorption at ∼225 °C onto a DB-1701 megabore
column in a Hewlett-Packard (HP) 5710 GC, initially held at
-
40 °C and then temperature programmed to 200 °C at 8 °C
+
-
1
([M + H] ) and their protonated homo- and heterodimers
min . In addition, an Entech 7000 preconcentrator (Entech
Instruments, Inc.) with a cold trap dehydration method was
used to transfer gas samples collected from the chamber
onto Tenax-TA solid adsorbent to a 30-m DB-1701 fused
silica capillary column in an HP 5890 GC interfaced to a HP
(
35).
For the OH radical reactions, the initial concentrations of
ONO, NO, and 1,3-butadiene (or 1,3-butadiene-d ) were
4.8 ×10 molecule cm each, and irradiations were carried
out for 2 min at 20% of the maximum light intensity. For the
NO radical reactions, the initial 1,3-butadiene (or 1,3-
butadiene-d
CH
∼
3
6
1
3
-3
5
971A mass selective detector operating in the scanning mode
3
for GC-MS analyses. GC-FID response factors were deter-
mined as previously described (34).
1
3
6
-
) and NO
2
concentrations were ∼4.8 × 10
molecule cm each, and one addition of N (corresponding
to an initial concentration of N in the chamber of (2.2-
3
2
O
5
For the NO
by the thermal decomposition of N
3
radical reactions, NO
3
radicals were generated
, and the initial 1,3-
2
O
5
2
O
5
1
3
-3
1
3
3.9) × 10 molecule cm ) was made to the chamber during
butadiene and NO
2
concentrations were (5.7-6.0) × 10 and
1
3
-3
the experiment.
∼
4.8 × 10 molecule cm , respectively. Three additions of
Chem icals. The chemicals used and their stated purities
were as follows: acrolein (99+%), Aldrich Chemical Co.; 1,3-
N
2
O [corresponding to initial concentrations of N O in the
5
2
5
1
3
-3
chamber of (0.82-1.32) × 10 molecule cm ] were made
to the chamber during an experiment. The concentrations
of 1,3-butadiene and selected products were measured as
described above.
butadiene (g99.0%), NO (g99.0%), and NO
Matheson Gas Products; and 1,3-butadiene-d (98%), Cam-
bridge Isotope Laboratories. Methyl nitrite, ethyl nitrite, and
were prepared and stored as described previously (29,
1, 34).
2
(g99.5%),
6
2 5
N O
3
Evacuable Cham ber Experim ents with FT-IR Analysis.
Four OH radical reactions were carried out in the 5870-L
evacuable, Teflon-coated chamber; two irradiations of CH
ONO-NO-1,3-butadiene-air mixtures and two irradiations
of C ONO-NO-1,3-butadiene-air mixtures at 740 Torr
total pressure and a relative humidity of <1%. The initial
3
-
Results
2
H
5
Gas Chrom atographic Analyses. GC-MS and GC-FID analy-
ses showed the formation of acrolein [CH
both the OH and NO
Because acrolein also reacts with the OH radical, the
measured acrolein concentrations in the OH radical-initiated
reactions were corrected to take into account secondary
reactions with the OH radical as described previously (36),
using rate constants for the reactions of the OH radical with
2
dCHCHO] from
3
radical reactions of 1,3-butadiene.
1
4
concentrations of the reactants were 2.46 × 10 molecule
-
3
cm each. The irradiations were carried out intermittently
with illumination periods of 0.5-1.25 min and total irradiation
times of 5-6.5 min. IR spectra were recorded prior to the
start of photolysis and during the intervening dark periods.
Each spectrum was recorded with 64 scans (corresponding
to 2.0-min averaging time), a full-width-at-half-maximum
-
11
1,3-butadiene and acrolein at 298 K of 6.66 × 10 and 1.99
-
1
-11
3
-1 -1
resolution of 0.7 cm , and a path length of 62.9 m (30, 34).
× 10 cm molecule
s , respectively (20-22). Corrections
In one of the CH
3
ONO-NO-1,3-butadiene-air irradiations,
for secondary reactions of acrolein with the OH radical during
1
4
-3
4
.9 × 10 molecule cm NO was added at the end of
the OH radical reactions were <14%. Corrections for the
irradiation and monitored in the dark by FT-IR spectroscopy
for 35 min.
secondary reaction of acrolein with the NO
the NO
formation yields obtained from the OH and NO
3
3
radical during
radical reactions were negligible (<1%). The acrolein
radical-
3
Two NO
3
radical experiments were performed by adding
1
3
13
-3
N
2
O
5
, in aliquots of 2.46 × 10 or 4.92 × 10 molecule cm
initiated reactions by least-squares analyses of the data
obtained are given in Table 1.
Analyses by FT-IR Spectroscopy. Reaction with the OH
Radical. The major products observed during the photolyses
1
4
-3
to 2.46 × 10 molecule cm 1,3-butadiene in 740 Torr total
pressure of air and by monitoring the reactants and products
by FT-IR spectroscopy after each N
of each of these two experiments, (2.5-7.4) × 10 molecule
2 5
O addition. At the end
1
4
of CH
3
2 5
ONO-NO-1,3-butadiene-air and C H ONO-NO-
VOL. 33, NO. 20, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3 5 8 7

TABLE 1. Products Identified and Their Formation Yields from the Reactions of 1,3-Butadiene with OH Radicals (in the Presence
of NO) and NO
3
Radicals at 298 ( 2 K and Atmospheric Pressure of Air
formation yield
product
GC-FIDa
FT-IRb
literature
reference
OH Radical Reaction
acrolein
0.61 ( 0.05
0.55 ( 0.05
0.98 ( 0.12c
Maldotti et al. (23)
Ohta (24)
∼
0.39
HCHO
furan
0.62 ( 0.05
0.03-0.04d
0.060 ( 0.020
Ohta (24)
0
.039 ( 0.011
Atkinson et al. (26)
organic nitrates
0.07 ( 0.03e
NO3 Radical Reaction f
acrolein
HCHO
0.039 ( 0.012
0.045
0.12
0.05
0.12
0.05
Barnes et al. (27)
Skov et al. (28)
Barnes et al. (27)
Skov et al. (28)
<
<
0.065
furan
0.014
organic nitrates
R(ONO2)(OONO2) species
0.63 ( 0.15
0.08-0.16
∼0.60
Barnes et al. (27)
a
Indicated errors are two least-squares standard deviations com bined with the estim ated overall uncertainties in the GC-FID response factors
for 1,3-butadiene and acrolein of (5% each. b Indicated errors are two least-squares standard deviations com bined with the estim ated overall
uncertainties in the IR calibrations for 1,3-butadiene, HCHO, and acrolein of (4, (4, and (5%, respectively. As reevaluated by Atkinson (22).d Yield
c
e
appeared to increase with the extent of reaction (see text). The presence of high NO
estim ate of the organic nitrates yield being high (because of the occurrence of R O˙ + NO
to reacted N -NO -NO -1,3-butadiene-air m ixtures.
2
concentrations during these reactions m ay result in this
2
reactions). From experim ents without addition of NO
f
2
O
5
3
2
FIGURE 2. Plots of formaldehyde, acrolein, and furan formed against
the amounts of 1,3-butadiene that reacted with OH radicals. The
formaldehyde and acrolein concentrations were corrected for
secondary reactions. Analyses were by FT-IR spectroscopy.
FIGURE 1. (A) Product spectrum from a 1,3-butadiene-CH ONO-
3
14
NO-air photolysis after 6.5 min of irradiation and 1.10 ×10 molecule
-
3
cm of 1,3-butadiene reacted (see text). (B) Residual spectrum
from spectrum A after subtraction of absorptions by acrolein (noted
by asterisks) and furan. (C) Difference between spectrum B and
residual spectrum after addition of excess NO to the reaction mixture.
for their reactions with OH radicals (36) using a rate constant
-
12
3
for reaction of the OH radical with HCHO of 9.37 × 10 cm
13
Numbers in parentheses are concentrations in units of 10 molecule
-
1
-1
-
3
-1
molecule
s
at 298 K (22), against the amounts of 1,3-
cm . (Gaps in the spectra in the 1615 and 1370 cm regions
correspond to strong absorptions by NO formed and by the
butadiene reacted are presented in Figure 2, and their
formation yields obtained from least-squares analyses of the
data are given in Table 1. Corrections for secondary reactions
with the OH radical were <9% for acrolein and <4% for
HCHO.
2
accumulated nitrate ions on the infrared windows, respectively.)
The absorbances of spectra A and B are displaced vertically for
clarity.
1
,3-butadiene-air mixtures were acrolein and formaldehyde.
Figure 1A shows infrared absorptions of acrolein among those
of other products from irradiation of a CH ONO-NO-1,3-
butadiene-air mixture after a total of 6.5 min of irradiation
the infrared absorptions of the remaining reactants, HCHO,
and the other photooxidation products of CH ONO (CH
ONO , HCOOH, NO , HNO , and HONO) have been sub-
tracted]. The HCHO formation yields were determined from
irradiations of C ONO-NO-1,3-butadiene-air mixtures.
Plots of the amounts of HCHO and acrolein formed, corrected
Furan was observed as a minor product with its formation
being indicated by the sharp Q-branch at 744.4 cm- in the
product spectrum (Figure 1A). As shown by the data from
four experiments plotted in Figure 2, the measured furan
concentrations increased nonlinearly with the extent of
irradiation, from being nondetectable after 1 min of photolysis
to a yield of ∼3-4% at the end of the 5-6.5-min total
irradiation times. Other products that could be deduced from
the residual spectrum shown in Figure 1B most likely contain
1
3
[
3
3
-
2
2
3
2
H
5
-1
-1
CdO (∼1720 and ∼1742 cm ), OH (∼1077 cm ), ONO
2
(1666,
3
5 8 8
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 33, NO. 20, 1999

shown in Figure 3B. In Figure 3A,B, the absorption bands of
the remaining 1,3-butadiene, NO , and observed minor
products HCHO, acrolein, furan, HNO , and HOONO (and
2
3
2
NO in Figure 3B) have been subtracted. In Figure 3,
subtraction of panel B from panel A resulted in panel C,
which shows the presence of characteristic absorptions by
-1
an ONO
group at 1724, 1298, and 791 cm , thus indicating the
formation of an R(ONO )(OONO )-type compound that
2 2
group at 1667, 1283, and 848 cm and by an OONO
-
1
2
2
decomposed in the presence of excess NO. There was no
significant difference in the integrated intensities of the 1285
-
1
cm band between the spectra taken at 30 and 60 min after
the addition of NO, and these intensities agreed, relative to
the amount of 1,3-butadiene reacted, with those from a
similar experiment where three times the above amount of
NO was employed. This indicates that the amount of
R(ONO
containing product(s) is fairly well approximated by Figure
, panels C and B. However, the addition of NO after N
had been consumed brought about further consumption of
,3-butadiene. Thus, for example, in the experiment repre-
2 2 2
)(OONO ) formed relative to the major ONO group
3
2 5
O
1
1
4
-3
sented in Figure 3, 1.07 × 10 molecule cm 1,3-butadiene
FIGURE 3. Product spectra from a reaction mixture of 1,3-butadiene
and N . (A) Residual spectrum depicting the major product(s)
was consumed after the addition of N , and an additional
2
O
5
2 5
O
1
3
-3
loss of 2.33 × 10 molecule cm 1,3-butadiene was recorded
14
-3
from 1.07 × 10 molecule cm of 1,3-butadiene consumed (see
text). (B) Residual spectrum after addition of excess NO to the
mixture. (C) Difference spectrum: spectrum A minus spectrum B.
The absorbances of spectra A and B are displaced vertically for
clarity.
6
1
0 min after the addition of NO to the reacted N
2
O
5
-NO -
2
,3-butadiene-air mixture.
The amount of ONO
2
group containing products was
approximated from Figure 3B and similar spectra with the
-1
use of the 1285 cm band (see the OH radical reaction above),
resulting in an average molar yield of 0.63 from the two
experiments that were conducted, relative to the amounts
of 1,3-butadiene consumed prior to the addition of NO. This
284, and 849 cm-1), and OONO
(1724, 1297, and 797 cm-1
;
1
2
see below) functional groups.
The total yield of products containing ONO
groups was estimated to be 0.08 ( 0.03 based on the
2
and OONO
2
estimate includes any RONO
2
product(s) arising from
-
1
R(ONO )(OONO ) decomposition [the formation of dinitrate
integrated area of the 1284 cm band (Figure 1B) and an
2
2
-
17
2 2 2
products R(ONO )(ONO ) after decomposition of R(ONO )-
(OONO ) is expected to be minor (20)] and any RONO formed
2 2
from the additional 1,3-butadiene consumed after the
addition of NO to the reacted N -NO -1,3-butadiene-
air mixture. Consideration of the reaction mechanisms
average integrated absorption coefficient of 1.3 × 10
molecule . This average value was derived from measure-
ments in this laboratory of the corresponding bands of CH
ONO , C ONO , CH CH CH ONO , and CH C(O)OONO
whose integrated absorption coefficients fall in the narrow
cm
-
1
3
-
H
5
2
3
2
2
2
3
2
,
2
O
5
2
2
2
-
17
-1
involved (20) [see also Discussion below] suggests that the
range of (1.1-1.4) × 10 cm molecule (30). The presence
1
,3-butadiene consumed after NO addition is primarily due
to reaction with OH radicals, in which case the ∼7% yield of
RONO found in the OH radical reaction (see above) would
translate to <3% contribution to the RONO products
represented in Figure 3B. On the assumption that the ONO
and OONO groups of R(ONO )(OONO ) contribute additively
and equally) to the intensity of the ∼1285 cm absorption
in Figure 3C, an average molar yield of 0.08 for R(ONO )-
of a product containing an OONO group was verified by the
2
set of characteristic bands seen in Figure 1C (2× scale), which
was obtained as the difference between the residual spectra
at the end of irradiation (Figure 1B) and at 35 min after the
addition of NO to the reaction mixture. No measurable loss
of 1,3-butadiene accompanied the decomposition of the
2
2
2
2
2
2
-
1
(
ROONO
of the 1297 cm peak in Figure 1C, a measure of the ROONO
formed, is a factor of ∼8 lower than the overall integrated
intensity of the 1284 cm band in Figure 1B, and correction
for this contribution leads to a yield estimate for the RONO
2
product in the presence of excess NO. The intensity
-1
2
2
(
OONO
2
) is estimated from the two experiments. With the
-
1
same assumption, a 1:1 conversion of R(ONO )(OONO ) to
2
2
an RONO
contribution to the ∼1285 cm band in Figure 3B, which is
half that contributed by R(ONO )(OONO ) to the same band
position in Figure 3A, and this leads to an upper-limit estimate
of the R(ONO )(OONO ) formed being twice the 0.08 molar
2
product would then result in an intensity
2
-
1
-
1
product of 0.07 ( 0.03. The presence of the 1059 cm band
in Figure 1C suggests that the ROONO compound contains
2
2
2
a hydroxyl group, and the possible presence of two overlapped
-
1
bands in each of the regions around 1059 and 1724 cm
could indicate two positional isomers for the ROONO
2
2
yield determined above. Hence, under the conditions of these
experiments the actual yield of R(ONO )(OONO ) is probably
in the range 0.08-0.16. Consideration of this uncertainty in
the R(ONO )(OONO ) yield leads us to cite the organic nitrate
yield as 0.63 ( 0.15.
The average molar formation yields of HCHO, acrolein,
and furan from the two N -NO -1,3-butadiene-air
2
formed. The occurrence of two distinct bands at ∼1720 and
2
2
-
1
∼
1742 cm in Figure 1B suggests the presence of two
products containing a CdO group, with the lower frequency
being most likely associated with a carbonyl compound
containing a conjugated CdO group.
2
2
Reaction with the NO
from reacting N -NO -NO
showed that all of the N in each addition had reacted
3
Radical. The IR spectra obtained
2
O
5
2
2
O
5
3
2
-1,3-butadiene-air mixtures
experiments obtained prior to the addition of NO were 0.065,
0.045, and 0.014, respectively. Therefore, prior to the addition
2
O
5
during the 3-min mixing time. Figure 3A depicts the
absorption bands of the major product(s) after a total of 9.84
of NO, the reaction of the NO
leads to the formation of HCHO, acrolein, furan, organic
nitrates (RONO ), and nitrooxy-peroxynitrates (R(ONO )-
(OONO )) with measured or estimated molar yields of 0.065,
0.045, 0.014, 0.63 ( 0.15, and 0.08-0.16, respectively. These
products thus account for ∼87 ( 16% of the total reaction
3
radical with 1,3-butadiene
1
3
-3
×
10 molecule cm of N
been added to 2.46 × 10 molecule cm of 1,3-butadiene.
2
O
5
, in four equal aliquots, had
2
2
1
4
-3
2
A similar spectrum obtained 60 min after the addition of
1
4
-3
2
.46 × 10 molecule cm of NO to the above mixture is
VOL. 33, NO. 20, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3 5 8 9

TABLE 2. Products Formed from the OH and NO
3
Radical-Initiated Reactions of 1,3-Butadiene And 1,3-butadiene-d
6
Using in Situ
API-MS and API-MS/MS Analyses
products
reaction
1,3-butadiene
acrolein (MW 56)
1,3-butadiene-d6
acrolein-d4 (MW 60)
OH radical
a
HOCH2CHdCHCHO and isom ers
MW 86)
HOCH2CHdCHCH2ONO2 and isom ers
MW 133)
acrolein (MW 56)
,2-epoxy-3-butene (MW 70)
HOCH2CHdCHCHO and isom ers
MW 86)
O2NOCH2CHdCHCHO and isom ers
MW 131)
O2NOCH2CHdCHCH2OH and isom ers
MW 133)
O2NOCH2CHdCHCH2OOH and isom ers
MW 149)
HOCD2CD)CDCDO and isom ers
(
(MW 91)
b
HOCD2CD)CDCD2ONO2 and isom ers
(MW 139)
(
NO3 radical
acrolein-d4 (MW 60)
1,2-epoxy-3-butene-d6 (MW 76)
HOCD2CD)CDCDO and isom ers
(MW 91)
1
c
(
O2NOCD2CDdCDCDO and isom ers
(MW 136)
O2NOCD2CDdCDCD2OH and isom ers
(MW 139)
(
c
(
c
O2NOCD2CDdCDCD2OOH and isom ers
(
(MW 155)
a
Because rapid -OD to -OH exchange occurs under our experim ental conditions, we cannot distinguish between reactions 9 and 10 as a
b
form ation route to this product. Note that the H-atom in the -OH group arises from OH radical addition, and hence no -OD/-OH exchange occurred.
Rapid -OD to -OH exchange occurs under our experim ental conditions.
c
products. The presence of a distinct absorption at 1722 cm-
1
MS analyses of the products of the reactions of OH radicals
6
and NO radicals with 1,3-butadiene and 1,3-butadiene-d .
in Figure 3B indicates the presence of a CdO group, most
3
likely conjugated, in the major RONO
2
product(s). The
Product peaks were identified based on the observation of
+
formation of other carbonyl products is not ruled out,
including that indicated by a weak band envelope near 1753
homo- or heterodimers (for example, [(MP1
+ H] , and [MP1 + MP2 + H] , where P1 and P2 are products)
in the API-MS/ MS parent ion spectra and on consistency of
)
2
+ H] , [(MP2
)
2
+
+
-
1
-1
cm . The 1834 cm band cannot be assigned to a plausible
carbonyl product and is believed to be a combination band.
the API-MS/ MS daughter ion spectrum of a homo- or
+
After addition of NO to these reacted N
2
O
5
-NO
2
-1,3-
P
heterodimer ion with the parent ion spectra of the [M + H]
butadiene-air mixtures, the HCHO, acrolein, and furan
formation yields increased to 0.17, 0.13, and 0.059, respec-
tively, relative to the overall amount of 1,3-butadiene
ion peaks (35). Water cluster ion peaks of the product ions,
+
[M + H + H
2
O] , were also observed in some instances.
The products observed from the reactions of 1,3-butadiene
and 1,3-butadiene-d with OH and NO radicals are listed in
consumed. The addition of NO to reacted N
butadiene-air mixtures leads to the decomposition of the
R(ONO )(OONO ) compounds, with concurrent generation
of OH radicals from the reactions of nitrooxyalkoxy radicals,
R(ONO ) O˙ , in the presence of NO (see Discussion below).
Although, as discussed below, decomposition of R(ONO )-
OONO ) species could form HCHO, acrolein, and furan, the
2
O
5
-NO
2
-1,3-
6
3
Table 2. The evidence for the formation of these products,
in the form of API-MS and API-MS/ MS data of molecular
ions, the dominant fragment ions, and the presence of homo-
and heterodimers formed in the API-MS under the conditions
used were obtained in a manner similar to previous product
studies conducted in this laboratory (see, for example, ref
35). In agreement with the GC and FT-IR analyses, acrolein
2
2
2
2
(
2
additional amounts of HCHO and acrolein formed could be
totally accounted for by assuming that all of the 1,3-butadiene
consumed after the addition of NO was due to reaction with
OH radicals, using the HCHO and acrolein yields (Table 1)
(and acrolein-d
and NO radical reactions. In addition, HOCH
(and/ or its isomers) and HOCH CHdCHCH ONO
2
4
) was observed as a product of both the OH
CHdCHCHO
(and/ or
3
2
2
2
obtained from CH
3
ONO (or C
2
H
5
ONO)-NO-1,3-butadiene-
its isomers) were observed as products of the OH radical
with 1,3-butadiene, with the deuterated analogues being
formed from the reaction of the OH radical with 1,3-
air irradiations. Only a fraction of the additional furan formed
could be accounted for by the ∼3-4% furan yield from the
reaction of the OH radical with 1,3-butadiene, and most of
the additional furan observed after the addition of NO must
butadiene-d
are shown in Figures 4 and 5 for the OH radical reactions
with 1,3-butadiene and 1,3-butadiene-d . These parent ion
6
. Representative API-MS/ MS parent ion spectra
be formed from the reactions of R(ONO
other undetermined products. If assumed as arising from
the R(ONO )(OONO ) species, furan yields of 0.44 and 0.70
were calculated from the two experiments on the basis of the
estimated R(ONO )(OONO ) yield of 0.08, and half of these
formation yields if the R(ONO )(OONO ) yield was 0.16. The
2
)(OONO
2
) and/ or
6
spectra demonstrate how evidence for the three products
formed in the OH radical reaction was obtained, with
homodimers of acrolein evident at 113 u in Figure 4A and
2
2
2
2
2
homodimers of HOCH CHdCHCHO (and/ or its isomers of
2
2
molecular weight 86) at 173 u in Figure 5A. The dimer ions
in Figures 4A and 5A clearly show a total of three products
with the molecular weight 133 species being attributed to
HOCH CHdCHCH ONO (and/ or its isomers). The deuter-
2 2 2
ated analogues in Figures 4B and 5B are consistent with these
assignments, with the dimers shown in Figure 5B being
cause of the difference in the furan yields, after the addition
of NO from the two experiments could not be determined.
1
4
Reaction with NO
2
. A mixture of 2.46 × 10 molecule
cm- 1,3-butadiene in air with 1.8 × 10 molecule cm NO
3
14
-3
2
resulted in a loss of ∼3% of the initial 1,3-butadiene after 90
min in the dark. The weak IR product spectrum showed that
dimers of HOCD
2
CDdCDCDO due to rapid D/ H exchange
the product(s) formed contained both NO
2
(∼1360 and ∼1580
for the alcohol if the initially formed species was DOCD -
CDdCDCDO (see Discussion below). MS/ MS spectra of the
2
-
1
-1
cm ) and ONO
2
(792, 1297, and 1725 cm ) groups. The
slow reaction observed indicates that the extents of reaction
of 1,3-butadiene with NO in the OH and NO radical-initiated
reactions described above were negligible.
API-MS Analyses. API-MS/ MS daughter ion and parent
ion spectra were obtained for ion peaks observed in the API-
dimer peaks confirmed their identity.
2
3
The NO
butadiene-d
being acrolein, 1,2-epoxy-3-butene, HOCH
NOCH CHdCHCHO, O NOCH CHdCHCH
2
3
radical reactions with 1,3-butadiene and 1,3-
6
each led to the formation of six products: these
2
CHdCHCHO, O
OH, and O
2
-
-
2
2
2
2
3
5 9 0
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 33, NO. 20, 1999

FIGURE 5. API-MS/MS CAD parent ion spectra of (A) the 87 u [M
2
FIGURE 4. API-MS/MS CAD parent ion spectra of (A) the 57 u [M
1
+
+
+ H] ion observed in the API-MS spectrum of an irradiated CH -
+
H] ion observed in the API-MS spectrum of an irradiated CH
3
+
-
3
+
ONO-NO-1,3-butadiene-air mixture, and (B) the 92 u [M + H]
2
ONO-NO-1,3-butadiene-air mixture and (B) the 61 u [M
ion observed in the API-MS spectrum of an irradiated CH
NO-1,3-butadiene-d -air mixture. The (unlabeled) ions peaks at
27 (A) and 137 u (B) are attributed to loss of HNO from the 190 and
00 u dimer ions, respectively. M is acrolein, M is HOCH CHd
CHCHO and isomers, and M is HOCH CHdCHCH ONO and isomers.
1
+ H]
ion observed in the API-MS spectrum of an irradiated CH
NO-1,3-butadiene-d -air mixture. M , M , and M are as given in
the caption for Figure 4.
3
ONO-
3
ONO-
6
1
2
3
6
1
3
2
1
2
2
3
2
2
2
Note the increases in mass for the corresponding deuterated
products shown in panel B (see Table 2 for details).
NOCH
2 2
CHdCHCH OOH (and/ or their isomers) for the 1,3-
butadiene reaction, and analogously for the 1,3-butadiene-
d
6
reaction. Figure 6 shows the API-MS/ MS daughter ion
+
spectra of the [M + H] ion peaks of the molecular weight
1
31 and 133 u products attributed to O
2 2
NOCH CHdCHCHO
(
and isomers) and O NOCH CHdCHCH
2
2
2
OH (and isomers),
+
2
respectively (note the presence of intense 46 u [NO ]
fragment ions and fragments corresponding to losses of
HNO ).
3
Of particular interest is that the API-MS/ MS daughter ion
+
spectra of the [M + H] ions of the molecular weight 86
products from the 1,3-butadiene reactions with OH and NO
3
radicals are virtually identical (Figure 7) and similarly for the
molecular weight 133 products. This is also the case for the
+
API-MS/ MS daughter ion spectra of the [M + H] ions of the
corresponding molecular weight 91 and 139 products from
the 1,3-butadiene-d
6
reactions, as shown in Figure 8 for the
radical-
+
1
40 u [M + H] ion peaks from the OH and NO
3
initiated reactions. Thus, the dominant hydroxycarbonyl(s)
and hydroxynitrate(s) from the OH and NO
may be the same.
3
radical reactions
Discussion
FIGURE 6. API-MS/MS CAD daughter ion spectra of (A) the 132 and
B) the 134 u ion observed in the API-MS spectra of reacted N
NO
1 u (B) are attributed to loss of HNO
OH Radical Reaction. The reaction of the OH radical with
(
2 5
O -
1
,3-butadiene proceeds by initial addition (20-22)
3
-NO -1,3-butadiene-air mixtures. Fragment ions at 69 (A) and
2
7
3
, and the 46 u fragment ions
+
are attributed to NO
NOCH
isomers.
2
. These spectra are attributed to protonated
O
2
2 2 2 2
CHdCHCHO (A) and O NOCH CHdCHCH OH (B) and/or their
leading, after addition of O
hydroxyalkyl peroxy radicals HOCH
CHCH(OH)CH O˙ , and HOCH CHdCHCH
2
, to the formation of the three
CH( O˙ O)CHdCH , CH
O˙ . In the pres-
2
2
2
d
2
2
2
2
2
VOL. 33, NO. 20, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3 5 9 1

FIGURE 7. API-MS/MS CAD daughter ion spectra of the 87 u ions
attributed to protonated HOCH CHdCHCHO and/or its isomers)
observed in the API-MS spectra of (A) an irradiated CH ONO-
NO-1,3-butadiene-air mixture and (B) a reacted N -NO -NO
,3-butadiene-air mixture.
FIGURE 8. API-MS/MS CAD daughter ion spectra of the 140 u ions
(attributed to protonated HOCD CDdCDCD ONO and/or its isomers)
observed in the API-MS spectra of (A) an irradiated CH ONO-
NO-1,3-butadiene-d -air mixture and (B) a reacted N -NO
NO -1,3-butadiene-d -air mixture. The fragment ions at 92 u are
attributed to a loss of DNO
(
2
2
2
2
3
3
2
O
5
3
2
-
6
2
O
5
3
-
1
2
6
2
.
ence of NO, these peroxy radicals react with NO to form
SCHEME 1
either the corresponding hydroxyalkoxy radical plus NO
the hydroxyalkyl nitrate. For example:
2
or
The resulting hydroxyalkoxy radicals HOCH
CH dCHCH(OH)CH O˙ , and HOCH CHdCHCH
compose, isomerize, or react with O (20), with not all of
2
CH( O˙ )CHdCH
2
,
2
2
2
2
O˙ can de-
2
to form the unsaturated hydroxycarbonyl HOCH
CHCHO. In addition, it is also possible that cis-HOCH
2
2
CHd
CHd
these processes being possible for all three hydroxyalkoxy
radicals formed from 1,3-butadiene. It is anticipated (20)
CHCHO and/ or the O˙ CH
with elimination of water to form furan (26, 37), as shown
in Scheme 1. Furan formation from the O˙ CH CH(OH)CHd
CH radical would be expected to lead to a constant yield of
furan formation during the reactions, while formation of furan
from cis-HOCH CHdCHCHO would be expected to result in
2 2
CH(OH)CHdCH radical cyclizes
that the HOCH
2
2 2 2
CH( O˙ )CHdCH and CH dCHCH(OH)CH O˙
radicals will primarily decompose
2
2
2
a furan yield that increases with reaction time (and hence
with the extent of reaction).
In the present study, acrolein, HCHO, and furan were
identified and quantified by GC-FID and/ or in situ FT-IR
analyses (Table 1) with the formation yields of acrolein
measured by GC-FID and by in situ FT-IR spectroscopy being
in good agreement (Table 1). Furthermore, our measured
formation yields for HCHO and acrolein are similar (Table
1
), consistent with HCHO and acrolein being coproducts as
to form acrolein plus HCHO and that the HOCH
CHCH O˙ radical will react with O or isomerize (if confor-
mationally possible)
2
CHd
expected from reactions 7 and 8. The slightly higher HCHO
formation yield as compared to that of acrolein could arise
from the formation of HCHO from secondary reactions of
first-generation products, including from acrolein (22). Our
API-MS and API-MS/ MS analyses of the OH radical-initiated
2
2
reactions of 1,3-butadiene and 1,3-butadiene-d
also indicated the formation of HOCH CHdCHCHO (and/
or its isomers) and C NO nitrates (for example, HOCH
CHdCHCH ONO ), and these API-MS and API-MS/ MS
analyses are substantiated by the FT-IR spectroscopic
6
(Table 2)
2
4
H
7
4
2
-
2
2
3
5 9 2
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 33, NO. 20, 1999

analyses that also show the formation of organic nitrates
Table 1) and provide confirmatory evidence for the presence
SCHEME 2
(
of carbonyl compounds other than acrolein and HCHO.
The formation yields of acrolein and furan measured in
previous literature studies (23, 24, 26) are also given in Table
1
for comparison with our present data. As evident from
Table 1, our acrolein formation yield of 0.58 ( 0.04 (average
of the GC-FID and FT-IR analyses) lies between the previous
measurements of Maldotti et al. (23) and Ohta (24). In the
study of Maldotti et al. (23), the acrolein formation yield was
derived (20, 22) from the observation that the maximum
studies in the absence of added NO, RO˙
2
+ NO
2
, RO˙
2
+ RO˙
2
concentration of acrolein in irradiated NO -1,3-butadiene-
x
and RO
2
+ HO
2
radical reactions occur (note that in the
+ HO radical
reactions will occur) (20, 22). The reactions of the nitrooxyalkyl
peroxy radicals with NO lead to the formation of thermally
unstable nitrooxyalkyl peroxynitrates, as, for example:
air mixtures was 59 ( 7% of the initial 1,3-butadiene
concentration and the use of rate constants for the reactions
of 1,3-butadiene and acrolein with the OH radical [making
the reasonable assumption that the dominant loss process
for both 1,3-butadiene and acrolein was by reaction with the
OH radical (22, 23)]. The reasons for the discrepancies
between our present study and those of Maldotti et al. (23)
and Ohta (24) are not clear, but an acrolein formation yield
of significantly less than unity is consistent with our API-MS
and FT-IR analyses showing the formation of other products
atmosphere it is probable that mainly RO˙
2
2
2
O NOCH CHdCHCH O˙ +
2
2
2
2
NO a O NOCH CHdCHCH OONO (11)
2
2
2
2
2
which act as a temporary reservior of RO˙
Taking the O NOCH CHdCHCH O˙ radical as an example,
the expected R O˙ + R O˙ and RO + HO radical reactions are
as shown Scheme 3.
The other two nitrooxyalkyl peroxy radicals O
CH(O O˙ )CHdCH and CH dCHCH(ONO )CH O˙ will react
by analogous reaction schemes with the nitrooxyalkoxy
radicals formed being CH dCHCH( O˙ )CH ONO and CH
CHCH(ONO )CH O˙ . These two nitrooxyalkoxy radicals are
expected to decompose or react with O , as for example
2
radicals (see below).
2
2
2
2
(
2 2 2 2
nam ely HOCH CHdCHCHO, HOCH CHdCHCH ONO ,
2
2
2
2
and/ or their isomers). Our present and previous (26) product
formation yield data given in Table 1 combined with our
API-MS and API-MS/ MS analyses indicate that the reaction
products are HCHO plus acrolein (58 ( 4%), furan (4 ( 1%),
and organic nitrates (7 ( 3%; see footnote “e” in Table 1),
with the remaining ∼35% of the reaction products being
attributed to the formation of the unsaturated hydroxycar-
2
2
NOCH -
2
2
2
2
2
2
2
2
2
d
2
2
2
2
bonyl HOCH CHdCHCHO (and/ or its isomers). Our inves-
tigation of the products and mechanism of the reaction of
the OH radical with 1,3-butadiene indicates that the reaction
mechanism is analogous to that of the corresponding reaction
of the OH radical with isoprene (2-methyl-1,3-butadiene)
(
20, 26, 30, 38). Recently, Liu et al. (25) used a derivatization
method, with O-pentafluorobenzylhydroxylamine as the
derivatizing agent, to investigate the products of the NO
x
-
air photooxidation of 1,3-butadiene. A series of carbonyl-
containing compounds were identified (or tentatively iden-
tified), including formaldehyde, acrolein (and its reaction
The HO
2
radicals formed from these nitrooxyalkoxy radical
reactions will react with NO, if added, to generate OH radicals:
4
products), and C -hydroxycarbonyl(s), as observed here. In
addition, furan, 1,2-epoxy-3-butene, and 1,2,3,4-diepoxybu-
tane were observed by gas chromatography (25).
HO + NO f OH + NO2
(14)
2
The products expected in the absence of added NO are
It is interesting to note that we have previously observed
that the formation yield of 3-methylfuran from the OH radical-
initiated reaction of isoprene in the presence of NO was
independent of the extent of reaction (26), in contrast to the
data for furan formation from 1,3-butadiene shown in Figure
therefore 1,2-epoxy-3-butene, HCHO + acrolein, O NOCH -
2
2
CHdCHCHO and its isomers, O NOCH CHdCHCH OH and
2
2
2
its isomers, O NOCH CHdCHCH OOH and its isomers, and
2
2
2
HOCH CHdCHCHO. The addition of NO to reacting N O -
2
2
5
NO -NO -1,3-butadiene-air mixtures converts nitrooxy-
3
2
2
. 3-Methylfuran has also been identified and quantified in
ambient air collected at a rural forested site (39), and the
-methylfuran and isoprene concentrations were consistent
alkyl peroxy radicals into the corresponding nitrooxyalkoxy
radicals (and forms a small amount of dinitrate via reactions
such as reaction 6a shown above for the OH radical-initiated
reaction of 1,3-butadiene), with the nitrooxyalkoxy radicals
expected to undergo decomposition, isomerization, or reac-
3
with the laboratory 3-methylfuran formation yield from
isoprene (26), suggesting that in the isoprene system 3-me-
thylfuran does not arise from C
are also isoprene reaction products (38)].
NO Radical Reaction. The NO radical reaction with 1,3-
butadiene is analogous to the OH radical reaction in that the
reaction proceeds by initial addition of the NO radical to
the carbon atoms of the >CdC< bonds (20). At low total
pressures or in the absence of O , the resulting nitrooxyalkyl
radical decomposes to NO plus an oxirane. In the presence
of O (for example, in 1 atm of air), the thermalized
nitrooxyalkyl radical reacts with O to form the nitrooxyalkyl
peroxy radical. Scheme 2 shows these reactions for the initial
NO radical addition to the 1-position in 1,3-butadiene.
Therefore, in addition to the possible formation of 1,2-epoxy-
-butene, the nitrooxyalkyl peroxy radicals O NOCH CH-
, and O NOCH
are expected to be formed. In laboratory
5
-hydroxycarbonyls [which
tion with O as shown in reactions 12 and 13 and Scheme
2
3.
3
3
For experiments carried out without addition of NO to
the reactant mixtures, our GC-FID and in situ FT-IR analyses
are in agreement with the previous studies of Barnes et al.
(27) and Skov et al. (28) that formation of HCHO and acrolein
is minor. The formation yields of acrolein measured here by
GC-FID and FT-IR are in good agreement, and as shown in
Table 1, our formation yields for HCHO and acrolein are
reasonably consistent with the previous data of Barnes et al.
(27) and Skov et al. (28). As may be expected, our IR spectra
of the reaction products (Figure 3A) appears to be essentially
identical to that presented by Skov et al. (28) [their Figure
1a], and the conclusions obtained from our FT-IR analyses
are in accord with those of Barnes et al. (27) and Skov et al.
(28) that the major products are organic nitrates. Thus, Barnes
3
2
2
2
2
3
3
2
2
(
O˙ O)CHdCH
2
, CH
2
2
dCHCH(ONO
2
)CH
2
O˙
2
2
2
-
CHdCHCH
2
O˙
VOL. 33, NO. 20, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3 5 9 3

SCHEME 3
et al. (27) estimated that the yield of organic nitrates was
intermediates in the NO
it is also clear that multifunctional products are formed in
large yield from these reactions; HOCH CHdCHCHO (and/
or its isomers) from the OH radical-initiated reaction and
unsaturated C -hydroxycarbonyls, hydroxynitrates, carbo-
nylnitrates, and nitrooxyhydroperoxides from the NO radi-
cal-initiated reaction. Given the short lifetime of 1,3-
butadiene in the atmosphere, these first-generation products
are therefore expected to be present in the ambient atmo-
sphere and to undergo further reactions.
3
radical-initiated reaction. However,
∼
60%, in agreement with our estimate of 63 ( 15% (Table
), while Skov et al. (28) from their in situ FT-IR analyses and
use of LiAlH to reduce carbonyl (and nitrooxy) groups to
hydroxyl groups concluded that the major products were
trans-O NOCH CHdCHCHO and O NOCH C(O)CHdCH
NOCH CHdCHCHO being formed in minor
1
2
4
4
2
2
2
2
2
,
3
with cis-O
2
2
amounts.
Our API-MS and API-MS/ MS analyses are generally
consistent with the above FT-IR data from our study as well
as Barnes et al. (27) and Skov et al. (28), showing the formation
of acrolein, HOCH
(
2
CHdCHCHO, O
and/ or its isomers), O NOCH CHdCHCH
CHdCHCH OOH (and/ or its iso-
2
NOCH
2
CHdCHCHO
Acknowledgments
2
2
2
OH (and/ or its
The authors gratefully acknowledge the University of Cali-
fornia Toxic Substances Research and Teaching Program and
the U.S. Environmental Protection Agency, Office of Research
and Development (Assistance Agreement R-825252-01-0) for
support of this research. While this research has been
supported in part by the U.S. Environmental Protection
Agency, it has not been subjected to Agency review and
therefore does not necessarily reflect the views of the Agency,
and no official endorsement should be inferred.
isomers) and O
2
NOCH
2
2
mers), together with 1,2-epoxy-3-butene. The formation of
these products is also consistent with the reaction schemes
shown above, and the NO radical-initiated reaction of 1,3-
3
butadiene is then analogous to the corresponding NO
reactions with isoprene (40).
The addition of NO to reacting N
butadiene-air mixtures under conditions such that an
appreciable amount of the reacted 1,3-butadiene was present
3
radical
2
O
5
-NO
3
-NO
2
-1,3-
as the reservoir species nitrooxy-peroxynitrates [R(ONO
2
)-
Literature Cited
(
OONO ) species] changed the product yields by significantly
2
increasing the formation yields of HCHO, acrolein, and furan.
The increased yields of HCHO and acrolein after NO addition
are expected because the nitrooxyalkyl peroxy radicals are
largely converted into nitrooxyalkoxy (R O˙ ) radicals, which
(1) Kao, A. S. J. Air Waste Manage. Assoc. 1994, 44, 683.
(
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2
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,3-butadiene can account for all of the additional HCHO
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furan from the OH radical-initiated reaction of 1,3-butadiene
has been postulated to occur from the cyclization of cis-
HOCH
cal (26, 37) (Scheme 1), these processes are unlikely to account
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(
7) Kirchstetter, T. W.; Singer, B. C.; Harley, R. A.; Kendall, G. R.;
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(
(
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3
(
(
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1
990, 11, 1071.
O
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2 2 2
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(
(
(
(
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