Table S1
– Photooxidation products from low
-NO
x
Structure
Name
Abbreviation
Molecular
Weight
Detected at
By CIMS
α
-
pinene
hydroperoxide
APINENEOOH
168.228
253
α
-
pinene hydroxyl
hydroperoxide
APINENEOHOOH
186.244
271
α
-
pinene
hydroperoxy
carbonyl
APINENEOOHO
184.228
269
a
-
pinene hydroxyl
dihydroper
oxide
APINENEOHOOHOOH
218.244
303
Pinonaldehyde
PINON
168.288
(+) 169
Pinonic acid
PINON
ACID
184.228
203, 269
Ratio of 9
:1 for
203
:269
Pinonic peracid
PINON
PERACID
200.228
219, 285
Ratio 1:4 for 219:285
O
H
OO
H
O
H
OO
H
OO
H
O
OO
H
O
2
O
H
OO
H
O
O
O
O
OO
H
O
O
O
H
OO
H
O
H
OO
H
10
-
hydroxy pinonic
acid
10-
OH PINON ACID
200.228
219, 285
C9OOH
172.218
257
Norpinonaldehyde
NORPINON
154.202
(+) 155
Table S2
– Kinetic model of low
-NO
x
α
-pinene photooxidation
Reaction
Rate constant /
photolysis rate
a,b
Reference
c
ν
→
22
H O
2 OH
h
6
1
2.25 10
jx
−
=
Sander, 2006
→
22
2
2
OH + H O
HO + H O
12
1
1.8 10
kx
−
=
Sander, 2006
→
2
2
22
2
HO + HO
H O + O
12
2
2.5 10
kx
−
=
Sander, 2006
→
22
OH + OH
H O
12
3
6.28 10
kx
−
=
Sander, 2006
→
2
22
OH + HO
O + H O
10
4
1.1 10
kx
−
=
Sander, 2006
→
APINENE + OH
APINENEOH
11
5
4.8 10
kx
−
=
d
Atkinson, 2006
→
2
APINENE + H O
12
6
5.4 10
kx
−
=
d
Atkinson, 2006
11
5.34 10
total
kx
−
=
→
2
APINENE + O
APINENEOO
Instantaneous
→
22
APINENEOO + HO
APINENEOOH + O
11
7
1.2 10
kx
−
=
→
Products
12
8
8.0 10
kx
−
=
11
2.0 10
total
kx
−
=
→
2
APINENEOH + O
APINENEOHOO
Instantaneous
O
O
O
H
H
O
OO
H
O
O
O
→
2
APINENEOHOO + HO
APINENEOHOOH
12
9
5.1 10
kx
−
=
→
22
PINON + O + OH + HO
12
10
4.0 10
kx
−
=
→
APINENEOHOOHOOH
13
11
4.2 10
kx
−
=
→
APINENEOH other products
11
12
1.05 10
kx
−
=
11
2.0 10
total
kx
−
=
→
APINENEOHOO + APINENEOHOO
Products
12
13
2.0 10
kx
−
=
ν
→
APINENEOHOOH
PINON + OH
h
6
2
1.46 10
jx
−
=
→
APINENEOHOOH + OH
PINON
11
14
1.2 10
kx
−
=
→
2
APINENEOHOO + H O
11
15
1.1 10
kx
−
=
→
APINENEOHOOH
12
16
2.4 10
kx
−
=
11
2.54 10
total
kx
−
=
→
2
APINENEOHOOH + O
APINENEOHOOHOO
Instantaneous
ν
→
PINON
Products
h
6
3
7.26 10
jx
−
=
Atkinson, 2006
→
2
PINON + OH
PINON + H O
11
17
3.7 10
kx
−
=
Atkinson, 2006
Davis, 2007
→
2
PINON + O
PINONOO
Instantaneous
→
23
PINONOO + HO
PINON ACID + O
12
18
5.0 10
kx
−
=
→
2
PINON PERACID + O
12
19
5.0 10
kx
−
=
→
2
C9OOH + CO
12
20
2.8 10
kx
−
=
→
NORPINON
12
21
2.2 10
kx
−
=
→
Products
12
22
5.0 10
kx
−
=
11
2.0 10
total
kx
−
=
→
APINENEOOH + OH
APINENEOOHOH
11
23
4.0 10
kx
−
=
→
2
APINENEOOHOH + O
APINENEOHOOHOO
Instantaneous
→
22
APINENEOHOOHOO + HO
APINENEOHOOHOOH + O
11
24
1.1 10
kx
−
=
→
Products
12
25
9.0 10
kx
−
=
11
2.0 10
total
kx
−
=
→
APINENEOOHOHOOH + OH
Products
11
26
4.0 10
kx
−
=
a
Units: Rate constants cm
3
molecule
-1
s
-1
, photolysis rates s
-1
b
Photolysis rates calculated from absorption cross sections and the spectral radiance of the chamber lights
c
Reactions without a reference listed were determined here, see text for details
d
Total
Rate constant
for α
-pinene + OH (
k
5
+ K
6
) is
from the Atkinson, 2006. Each individual rate constant
represents the branching ratio of the reaction between OH addition to the double bond and H
-abstraction by
OH.
Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., J
enkin, M. E., Rossi, M.
J., and Troe, J.: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II -
gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625
-4055, 2006.
Davis, M. E., Talukdar, R. K., Notte, G., Ellison, G. B., and Burkholder, J. B.: Rate coefficients for the OH
plus pinonaldehyde (C
10
H
16
O
2
) reaction between 297 and 374 K, Environ. Sci. Technol., 41, 3959
-
3965, 2007.
Sander, S. P., Finlayson
-Pitts, B. J., Friedl, R. R., Golden, D. M., Huie, R. E., Kolb, C. E.
, Kurylo, M. J.,
Molina, M. J., Moortgat, G. K., Orkin, V. L., and Ravishankara, A. R.: Chemical kinetics and
photochemical data for use in atmospheric studies, evaluation number 15, Jet Propulsion
Laboratory, Pasadena, CA, 2006.
Figure S
1 – Photolysis
of H
2
O
2
(A) by black lights in the Caltech environmental chamber and
Consumption of α
-
pinene by OH (B) during the same experiment. In each case the black squares are
the data and the red line is the simulation from the kinetic model from Table S2. The co
ncentration of
α
-pinene is plotted on a log scale to show the first order kinetics.
0
2
4
6
8
10
12
0.1
1
10
Concentration (ppb)
Time (hours)
B
Concentration (ppm)
0
5
10
15
2.5
3.0
3.5
4.0
4.5
A
Figure S2 –
Proposed mechanism of peroxy radical isomerization
from addition of OH to either the
tertiary or secondary carbon of the double bond of
α
-pinene.
O
O
H
H
O
OO
H
O
H
OO
H
O
H
OO
H
O
H
O
H
O
O
H
O
H
OO
H
O
H
OO
H
OO
O
H
OO
H
OO
H
O
H
OO
H
OO
H
O
OO
H
OO
H
O
H
,
O
2
I
so
m
e
r
i
z
a
ti
o
n
se
v
e
n m
e
m
b
e
r
r
i
n
g
i
n
t
e
rm
e
d
i
a
t
e
O
2
H
O
2
O
H
,
O
2
I
so
m
e
r
i
z
a
ti
o
n
se
v
e
n m
e
m
b
e
r
r
i
n
g
i
n
t
e
rm
e
d
i
a
t
e
O
2
H
O
2
I
so
m
e
r
i
z
a
ti
o
n
s
i
x m
e
m
b
e
r
r
i
n
g
i
n
t
e
rm
e
d
i
a
t
e
O
2
-
H
O
2
-
O
2
-
O
2
OO
H
OO
Figure
S3 – Signal of pinonaldehyde from direct injection in the presence of 4 ppm H
2
O
2
photolyzed by
black lights. The simulation (red line)
incorporates both reaction with OH (k
OH
= 3.7 x 10
-11
cm
3
molecules
-1
s
-1
) and photolysis (
j
= 7.26 x 10
-6
s
-1
).
0
2
4
6
1
10
CIMS Signal (AU)
Time
(hours)