Kinetics and mechanism of the photooxidation of formaldehyde. 1. Flash photolysis study

Journal Article · Thu Mar 23 04:00:00 EST 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100343a033· OSTI ID:5143193

Veyret, B; Lesclaux, R; Rayez, M T; Rayez, J C ^[1]; Cox, R A ^[2]; Moortgat, G K ^[3]

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1. Universite de Bordeaux l, Talence (France)
2. Harwell Lab., Didcot, Oxfordshire (England)
3. Max Planck Institut fuer Chemie, Mainz (Germany, F.R.)

Transient species in the photooxidation of formaldehyde in air have been investigated by using the technique of flash photolysis kinetic spectroscopy. The absorption spectrum attributed to the HOCH{sub 2}O{sub 2} radical was observed with a maximum near 230 nm. This radical is formed by the reaction HO{sub 2} + HCHO {Longleftrightarrow} HOCH{sub 2}O{sub 2} (1, -1). The rate constants were measured for the two reactions: k{sub 1} = 7.7 {times} 10{sup {minus}15} exp((625 {plus minus} 550)/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} and k{sub {minus}1} = 2.0 {times} 10{sup 12} exp(({minus}7000 {plus minus} 2000)/T) s{sup {minus}1}. The equilibrium constant is K{sub 1}* = 3.85 {times} 10{sup {minus}27} exp(7625/T) cm{sup 3} molecule{sup {minus}1}, which corresponds to a reaction enthalpy {Delta}H{sub 1}{degree} = {minus}16.25 {plus minus} 0.30 kcal mol{sup {minus}1}, which is based on the K{sub p} value and quantum calculations of {Delta}S{sub 0}{degree} and therefore determined accurately. Kinetic measurements performed under various experimental conditions allowed determinations of the rate constants for the reactions HO{sub 2} + HOCH{sub 2}O{sub 2} {yields} products (3) and 2HOCH{sub 2}O{sub 2} {yields} O{sub 2} + CH{sub 2}(OH){sub 2} + HCOOH (4b); k{sub 3} = 5.6 {times} 10{sup {minus}15} exp((2300 {plus minus} 1100)/T); k{sub 4b} = 5.65 {times} 10{sup {minus}14} exp((750 {plus minus} 400)/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. The branching ratios for k{sub 3} and k{sub 4} were determined in separate experiments described in part 2 of this work.

• OSTI ID: 5143193
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:6; ISSN JPCHA; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
54 ENVIRONMENTAL SCIENCES
540110
ABSORPTION SPECTROSCOPY
ALDEHYDES
ATMOSPHERIC CHEMISTRY
BRANCHING RATIO
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
CROSS SECTIONS
DATA
DECOMPOSITION
EQUILIBRIUM
EXPERIMENTAL DATA
FORMALDEHYDE
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDATION
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
REACTION KINETICS
SPECTRA
SPECTROSCOPY
ULTRAVIOLET SPECTRA