Acrylic acid (CH2=CHC(O)OH) and methacrylates (CH2=C(CH3)C(O)OR), where R is an alkyl group, are widely used in the industry of polymers, paper coating, paint formulations , etc. In addition they are produced naturally by marine algae and in the rumen fluid of sheep.1 The atmospheric fate of unsaturated and oxygenated volatile organic compounds (VOCs) is mainly their reaction with OH radicals.2,3
As part of an ongoing program in our laboratory to study the atmospheric chemistry of oxygenated species, we report relative rate coefficients for the gas-phase reactions of OH radicals with acrylic acid (k1) and three unsaturated esters: methyl methacrylate (k2), ethyl methacrylate (k3) and n-butyl methacrylate (k4):
Kinetic experiments at room temperature and atmospheric pressure of air were performed using a relative-rate technique with GC-FID analysis. OH radicals were produced by the photolysis of CH3ONO in the presence of NO/O2.
Table 1: Reactant concentrations, kreactant/kref and k reactant for the reaction of OH with acrylic acid, methyl ethacrylate, ethyl methacrylate and n-buthyl methacrylate at 298 K in 760 Torr of air.
VOC |
[VOC]0 (ppm) |
Reference |
[Ref]0 (ppm) |
kreactant / kRef |
kreactant (cm3 molecule-1s-1) |
Acrylic acid |
63 |
3-chloropropene |
133 |
1.00 ± 0.06 |
(1.69 ± 0.17) x 10-11 |
|
64 |
Diethylether |
114 |
1.34 ± 0.07 |
(1.51 ± 0.09) x 10-11 |
|
|
average |
|
|
(1.60 ± 0.17) x 10-11 |
|
83 |
3-chloropropene |
83 |
2.47 ± 0.07 |
(4.17 ± 0.29) x 10-11 |
Methyl |
142 |
3-chloropropene |
126 |
2.48 ± 0.09 |
(4.19 ± 0.32) x 10-11 |
methacrylate |
85 |
3-chloropropene |
123 |
2.42 ± 0.08 |
(4.09 ± 0.30) x 10-11 |
|
|
average |
|
|
(4.15 ± 0.32) x 10-11 |
|
82 |
3-chloropropene |
83 |
2.59 ± 0.10 |
(4.38 ± 0.35) x 10-11 |
Ethyl |
139 |
3-chloropropene |
146 |
2.63 ± 0.19 |
(4.44 ± 0.50) x 10-11 |
methacrylate |
43 |
Diethyl ether |
109 |
3.49 ± 0.15 |
(4.75 |