Formaldehyde reaction with hydroxyl radicals

The primary process for BCME degradation in air is believed to be reaction with photochemically-generated hydroxyl radicals,. Reaction products are believed to include chloromethyl formate, C1HC0, formaldehyde and HC1 (Cupitt 1980 EPA 1987a). The atmospheric halflife due to reaction with hydroxyl radicals is estimated to be... 

Morris, E.D., Jr. and Niki, H. Mass spectrometric study of the reaction of hydroxyl radical with formaldehyde, J. Chem. Phvs., 55(4) 1991-1992, 1971. 

Further reaction of carbon monoxide with hydroxyl radical yields carbon dioxide (equation 8.35), whereas reaction of carbon monoxide with carbine yields ketene (equation 8.36) [14], Atomic hydrogen, in turn, converts carbon monoxide to formaldehyde (equations 8.37-8.38), which in principle may be a substrate for prebiotic... 

Reactions of formaldehyde and acetaldehyde with hydroxyl radicals... 

Hudson ER, Ticknor C, Sawyer BC, Taatjes CA, Lewandowski HJ, Bochinski JR, Bohn JL, Ye J. (2006) Production of cold formaldehyde molecules for study and control of chemical reaction dynamics with hydroxyl radicals. Phys. Rev. A. 73(6) 063404. 

Butkovskaya, N.I., Setser, D.W. Infrared chemiluminescence study of the reactions of hydroxyl radicals with formaldehyde and formyl radicals with H, OH, NO, and NO2. J. Phys. Chem. A 102, 9715-9728 (1998)... 

Stief, L.J., Nava, D.F., Payne, W.A., Michael, J.V. Rate constant for the reaction of hydroxyl radical with formaldehyde over the temperature range 228-362 K. J. Chem. Phys. 73, 2254-2258 (1980)... 

Different mechanisms to explain the disinfection ability of photocatalysts have been proposed [136]. One of the first studies of Escherichia coli inactivation by photocatalytic Ti02 action suggested the lipid peroxidation reaction as the mechanism of bacterial death [137]. A recent study indicated that both degradation of formaldehyde and inactivation of E. coli depended on the amount of reactive oxygen species formed under irradiation [138]. The action with which viruses and bacteria are inactivated by Ti02 photocatalysts seems to involve various species, namely free hydroxyl radicals in the bulk solution for the former and free and surface-bound hydroxyl radicals and other oxygen reactive species for the latter [139]. Different factors were taken into account in a study of E. coli inactivation in addition to the presence of the photocatalyst treatment with H202, which enhanced the inactivation... 

Iron-mediated generation of hydroxyl radical ( 0H) was monitored by the hypoxanthine-xanthine oxidase method as previously described (28). Formaldehyde produced by reaction of 0H with DMSO was determined spectrophotometrically by the Hantzsch reaction (29). 

I have spent some time trying to explore the experimental basis for such a reaction, and at the moment I feel that there is no good experimental foundation for writing it. From a structural point of view, it appears to be a highly unlikely reaction. The simplest example of such a reaction would be the reaction of methyl radicals with oxygen to produce formaldehyde, plus hydroxyl radical (Reaction 8)... 

Klein GW, Bhatia K, Madhavan V, Schuler RH (1975) Reaction of OH with benzoic acid. Isomer distribution in the radical intermediates.) Phys Chem 79 1767-1774 Klein SM, Cohen G, Cederbaum Al (1981) Production of formaldehyde during metabolism of dimethyl sulfoxide by hydroxyl radical generating systems. Biochemistry 20 6006-6012 Kumarathasan P, Vincent R, Goegan P, Potvin M, Guenette J (2001) Hydroxyl radical adduct of 5-aminosalicylic acid a potential marker of ozone-induced oxidative stress. Biochem Cell Biol 79 33-42... 

As Barr et al. (2003) pointed out, the importance of such emissions is determined mainly by their impact on the three processes taking place in the atmosphere. The first consists in that such NMHCs as isoprene form in the course of carboxylization in plants and contribute much thereby to the formation of biospheric carbon cycle. The second process is connected with NMHCs exhibiting high chemical activity with respect to such main oxidants as hydroxyl radicals (OH), ozone (03), and nitrate radicals (N03). Reactions with the participation of such components result in the formation of radicals of alkylperoxides (R02), which favor efficient transformation of nitrogen monoxide (NO) into nitrogen dioxide (N02), which favors an increase of ozone concentration in the ABL. Finally, NMHC oxidation leads to the formation of such carbonyl compounds as formaldehyde (HCHO), which stimulates the processes of 03 formation. Finally, the oxidation of monoterpenes and sesquiterpenes results in the intensive formation of fine carbon aerosol with a particle diameter of <0.4 pm... 

In ambient air, the primary removal mechanism for acrolein is predicted to be reaction with photochemically generated hydroxyl radicals (half-life 15-20 hours). Products of this reaction include carbon monoxide, formaldehyde, and glycolaldehyde. In the presence of nitrogen oxides, peroxynitrate and nitric acid are also formed. Small amounts of acrolein may also be removed from the atmosphere in precipitation. Insufficient data are available to predict the fate of acrolein in indoor air. In water, small amounts of acrolein may be removed by volatilization (half-life 23 hours from a model river 1 m deep), aerobic biodegradation, or reversible hydration to 0-hydroxypropionaldehyde, which subsequently biodegrades. Half-lives less than 1-3 days for small amounts of acrolein in surface water have been observed. When highly concentrated amounts of acrolein are released or spilled into water, this compound may polymerize by oxidation or hydration processes. In soil, acrolein is expected to be subject to the same removal processes as in water. 

This scheme of interrelated primary photochemical and subsequent radical reactions is comphcated by the back reaction of hydrogen atoms and hydroxyl radicals with formation of water (Fig. 7-16, reaction 2) or the dimerization of the latter with formation of hydrogen peroxide (Fig. 7-16, reaction 3). Furthermore, hydroxyl radicals are scavenged by hydroperoxyl radicals with formation of oxygen and water (Fig. 7-16, reaction 5) or by hydrogen peroxide to yield hydroperoxyl radicals and water (Fig. 7-16, reaction 4). In addition, hydroxymethyl radicals (HOCH ) formed by reaction 1 (Fig. 7-16) are able to dimerize with formation of 1,2-ethane-diole (Fig. 7-16, reaction 7) or they disproportionate to yield methanol and formaldehyde (Fig. 7-16, reaction 8). 

The temperature profile strongly influences those reactions whose rate coefficients have large activation energies. As will be shown in Sections IV, V, and VI, a number of reaction paths, while dominant in the lower troposphere, lose their importance with increasing altitude as the temperature drops sharply. Particularly affected are the altitude profiles of the hydroxyl radical, formaldehyde, and nitric oxide number densities. 

Two observations may be quoted in support of this proposal (Norman and Pritchett, 1966). First, phenethyl alcohol reacts at pH 1 to give the benzyl radical with no trace of the radical, PhCH2. OHOH which would be formed by abstraction of hydrogen from the hydroxyl-substituted carbon. Since the hydroxyl group activates adjacent C—H bonds towards abstraction by the hydroxyl radical, there is evidently a more rapid mode of reaction this could reasonably be the addition of OH to an aromatic carbon atom followed by acid-catalyzed elimination of formaldehyde and a proton ... 

Atmospheric concentrations are relatively high compared with other environmental compartments because of vinylidene chloride s high vapor pressure and low water solubility. The half-life for the chemical in air has been estimated to be 16 h and 2-3 days. Atmospheric hydroxyl radicals play a major role in its degradation. The major reaction products in air are formaldehyde, phosgene, and hydroxylacetyl chloride. 

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