Rate constants for OH reaction

The C-H bond strength is largest for primary C-H bonds at —101 kcal mol-1, decreasing to 98 kcal mol-1 for secondary and 96 kcal mol-1 for tertiary C-H bonds (Lide, 1998-1999). Hence one expects that, all else being equal, a tertiary C-H will react faster than a secondary C-H, which in turn will react faster than a primary C-H. Greiner (1970), whose measurements of the absolute rate constants for OH reactions in the mid-1960s provided the first clue of the potential importance of OH in the troposphere, suggested that... 

One example of a reactive HAP that is a pesticide is 1,3-dichloropropene, used as a soil fumigant for nematodes. Both the cis and trans forms react with OH and 03 (Tuazon et al., 1984), although the OH reaction is sufficiently fast that this reaction is expected to be the major atmospheric fate (see Problem 5). Thus, the rate constants for OH reaction with the cis and trans forms are 0.774 X 10 " and 1.31 X 10 " cm3 molecule-1 s-1, respectively, giving lifetimes with respect to OH at... 

Table 2 Rate constants for OH reactions with selected environmental contaminants...

The present paper tests the assumed original and enhancement mechanisms with rates and conversions for a broad range of contaminants measured under a fixed mass concentration (50 mg/m ) feed condition. The plots compared are reaction rates vs. (1) dark adsorption, Ot. (2) second order rate constant for (OH ) (TCE absent) or (Cl ) (TCE present), and (3) the product of these gas phase second order rate constant times the reactant dark coverage. Where a second order gas phase rate constant was not available, we estimated its value from correlations of kci vs. koH for tke same class of compounds. 

Figure 1 kci vs. koH- Second order gas phase rate constants for the reaction of Cl atoms vs. the corresponding OH radicals rate constants for the reactions with a. n-alkanes [11] b. n-alcohols [12] c. n-ethers [12] d. chloroethenes [13] and e. 1-chloroalkanes [14],... 

Figure 19. (a) Cluster size dependence of the rate constants for the reactions of CO2 with the large hydrated hydroxyl anions at T= 130 K O, experimental values for OH (H2O), —, calculated values for 0H (H20)n. (b) Dependence of rate constants on cluster size for the reactions of 0H (H20)n with SO2 at T = 135 K. Taken with permission from ref. 19. 

The principal pathway leading to degradation of acrylonitrile in air is believed to be photooxidation, mainly by reaction with hydroxyl radicals (OH). The rate constant for acrylonitrile reaction with OH has been measured as 4.1 x 10" cm /molecule/second (Harris et al. 1981). This would correspond to an atmospheric half-life of about 5 to 50 hours. This is consistent with a value of 9 to 10 hours measured in a smog chamber (Suta 1979). 

Harris GW, Kleindienst TE, Pitts JN Jr. 1981. Rate constants for the reaction of OH radicals with CfpCN, and CFfe = CH-CN in the temperature range 298-424 K. Chemical Physics Letters 80 479-483. 

Edney, E.O., Kleindienst, T.E., Corse, E.W. (1986) Room temperature rate constants for the reaction of OH with selected chlorinated and oxygenated hydrocarbons. Int J. Chem. Kinet. 18, 1355-1371. 

Ohta, T. (1983) Rate constants for the reactions of OH radicals with alkyl substituted olefins. Int. J. Chem. Kinet. 16, 879-886. 

Ohta, T. (1984) Rate constants for the reactions of diolefins with OH radicals in the gas phase. Estimate of the rate constants from those for monoolefins. J. Phys. Chem. 87, 1209-1213. 

Hansen, D.A., Atkinson, R., Pitts, J.N. Jr. (1975) Rate constants for the reaction of OH radicals with a series of aromatic hydrocarbons. J. Phys. Chem. 79, 1763-1766. 

The second-order rate constant for the reaction C02 +OH- = HCO -, k2 = 1.35 x 104 m3/kmols. Under the conditions stated, the reaction may be assumed pseudo first-order with respect to C02. 

Howard CJ, Evenson KM. 1976. Rate constants for the reactions of OH with CH4and fluorine, chlorine, and bromine substituted methanes at 296K. J Chem Phys 64 197-202. 

The rate constant for the reactions of H+ with many bases, and of OH with many... 

The reaction of OH with HFCs has attracted interest. The temperature dependence of the fast initial H abstraction by HO in HFCs has been calculated using ab initio methods. Rate constants calculated using HF and MP2(G-31G(d)) were found to be substantially greater than those determined experimentally. In other work investigating reactions of OH with HFCs, rate constants for its reactions with HFC-245cb (MeCFaCFs) and other fluoroalkenes have been determined. ... 

Photolytic. A photooxidation half-life of 26.7 d was based on an experimentally determined rate constant of 6 x 10 cmVmolecule-sec at 25 °C for the vapor-phase reaction of acetic acid with OH radicals in air (Atkinson, 1985). In an aqueous solution, the rate constant for the reaction of acetic acid with OH radicals was determined to be 2.70 x 10 cm /molecule-sec (Dagaut et al, 1988). 

Reported rate constants for the reaction of acetone with OH radicals in the atmosphere and in water are 2.16 x lO and 1.80 x 10 cm /molecule-sec, respectively (Wallington and Kurylo, 1987 Wallington et al., 1988a). Between 20 and 100 mmHg, reaction of acetone with OH radicals revealed no significant pressure dependence. Reaction products likely to form include acetic acid, methanol, methyl- and peroxy radicals (Wollenhaupt et al., 2000). 

Photolytlc. A rate constant of 4.94 x 10cmVmolecule-sec at 24 °C was reported for the vapor-phase reaction of acetonitrile and OH radicals in air (Harris et ah, 1981). Reported rate constants for the reaction of acetonitrile and OH radicals in the atmosphere and in water are 1.90 x lO" and... 

The rate constant for the reaction of butane and OH radicals in the atmosphere at 300 K is 1.6 x 10cmVmolecule-sec (Hendry and Kenley, 1979). Based upon a photooxidation rate constant of 2.54 X 10cmVmolecule-sec with OH radicals in summer daylight, the atmospheric lifetime is 54 h (Altshuller, 1991). At atmospheric pressure and 298 K, Darnall et al. (1978) reported a rate constant of 2.35-4.22 x 10 cmVmolecule-sec for the same reaction. A rate constant of 1.28 x 10 " L/molecule-sec was reported for the reaction of butane with OH radicals in air at 298 K, respectively (Greiner, 1970). At 296 K, a rate constant of 6.5 x lO cmVmolecule-sec was reported for the reaction of butane with NO3 (Atkinson, 1990). 

Photolytic. The rate constant for the reaction of sec-butyl acetate and OH radicals in the atmosphere at 300 K is 3.4 x lO cmVmolecule-sec (Hendry and Kenley, 1979). Chemical/Physical. Slowly hydrolyzes in water forming sec-butyl alcohol and acetic acid. 

The rate constants for the reaction of l,2-dibromo-3-chloropropane with ozone and OH radicals in the atmosphere at 296 K are <5.4 x 10 ° and 4.4 x lO cm /molecule-sec (Tuazon et al., 1986). The smaller rate constant for the reaction with ozone indicates that the reaction with ozone is not an important atmospheric loss of l,2-dibromo-3-chloropropane. The calculated photolytic half-life and tropospheric lifetime for the reaction with OH radicals in the atmosphere are 36 and 55 d, respectively. The compound l-bromo-3-chloropropan-2-one was tentatively identified as a product of the reaction of l,2-dibromo-3-chloropropane with OH radicals. 

Photolytic. Dimethylnitramine, nitrous acid, formaldehyde, V.V-dimethylformamide and carbon monoxide were reported as photooxidation products of dimethylamine with NOx. An additional compound was tentatively identified as tetramethylhydrazine (Tuazon et al., 1978). In the atmosphere, dimethylamine reacts with OH radicals forming formaldehyde and/or amides (Atkinson et al, 1978). The rate constant for the reaction of dimethylamine and ozone in the atmosphere is 2.61 x 10 cmVmolecule-sec at 296 K (Atkinson and Carter, 1984). 

Chemical/Physical. In the presence of nitric oxide, ethyl mercaptan reacted with OH radicals forming ethyl thionitrite. The rate constant for this reaction is 2.7 x 10 " at 20 °C (MacLeod et al, 1984). 

Photolytic. Fluorene reacts with photochemically produced OH radicals in the atmosphere. The atmospheric half-life was estimated to range from 6.81 to 68.1 h (Atkinson, 1987). Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of fluorene (25 tig/g substrate) using a rotary photoreactor. The photolytic half-lives of fluorene using silica gel, alumina, and fly ash were 110, 62, and 37 h, respectively. Gas-phase reaction rate constants for OH radicals, NO3 radicals, and ozone at 24 °C were 1.6 x lO , 3.5 x 10 and <2 x 10in cmVmolecule-sec, respectively (Kwok et al., 1997). 

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