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Title: Mechanisms for the reactions of OH with two unsaturated aldehydes: Crotonaldehyde and acrolein
Journal: J. Phys. Chem. A
Volume: 106
Page(s): 12252 - 12259
Year: 2002
Reference type: Journal article
Squib: 2002ORL/TYN12252-12259
Reaction:
CH2=CHCHO + ·OH → Products
Reaction order:
2
Pressure: 0.93 - 0.96 bar
Rate expression:
2.0x10-11 [cm3/molecule s]
Bath gas:
air
Category: Experiment
Data type:
Absolute value measured directly
Experimental procedure:
Static or low flow - Data taken vs time
Excitation technique:
Direct photolysis
Time resolution:
By end product analysis
Analytical technique:
Fourier transform (FTIR)
Comments:
Experiments were performed at the room tem[perature.
ABSTRACT:
The mechanisms for the reaction of OH with the unsaturated aldehydes, acrolein and crotonaldehyde, have been determined at 1 atm total pressure in the presence of NOx using an environmental chamber/FTIR spectrometer system. Products observed in the OH-initiated oxidation of acrolein were CO, CO2, CH2O, HOCH2CHO (glycolaldehyde), and HCOOH, while the major products identified in the OH-initiated oxidation of crotonaldehyde were CO, CO2, CH3CHO, and HC(O)CHO (glyoxal). Also observed were two PANtype species, identified as CH2dCH-C(O)O2NO2 (APAN) from acrolein oxidation and CH3-CHdCHC(O)O2NO2 (CPAN) from crotonaldehyde. The near-complete mass balance obtained in these experiments allows for a quantitative assessment of the branching ratios for abstraction and addition in these reactions. It is shown that about 68% (50%) of the OH reaction with acrolein (crotonaldehyde) proceeds via abstraction of the aldehydic H, with the remainder occurring via addition to the double bond. The data allow for a more accurate assessment of the atmospheric source strength of APAN, a species which has now been identified in ambient air. Trends in the reactivity of acrolein and its methylated derivatives, methacrolein and crotonaldehyde, are also discussed; data are shown to be consistent with structure-reactivity considerations.
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