A Critical Review of the Gas-Phase Reaction Kinetics of the Hydroxyl Radical

Abstract

The literature pertinent to reactions of the hydroxyl radical has been reviewed. An extensive discussion is given for reactions of the hydroxyl radical with itself and with CO, H₂, and CH₄. These four reactions are: $\text{(1)\hspace{0.17em}}\mathrm{OH}+\mathrm{OH}\to {\mathrm{H}}_2\mathrm{O}+\mathrm{O}\text{;\hspace{0.17em}(2)\hspace{0.17em}}\mathrm{CO}+\mathrm{OH}\to {\mathrm{CO}}_2+\mathrm{H}\text{;\hspace{0.17em}(3)\hspace{0.17em}}{\mathrm{H}}_2+\mathrm{OH}\to {\mathrm{H}}_2\mathrm{O}+\mathrm{H}\text{;\hspace{0.17em}(4)\hspace{0.17em}}{\mathrm{CH}}_4+\mathrm{OH}\to {\mathrm{CH}}_3+{\mathrm{H}}_2\mathrm{O}$ . Values are recommended for k₁ and k₂ and for the ratio k₃/k₂ and k₄/k₂. These rate ratios are used with the previously established value of k₂ to obtain recommended values for k₃ and k₄. The recommended values in cm³ mol^‐1·s^‐1, the temperature range, and the uncertainty are: $\begin{array}{c}{k}_1{\text{=1.55×10}}^{12}\text{,\hspace{0.17em}300\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log \text{\hspace{0.17em}k±0.1, 05}\\ k_2{\text{=3.1×10}}^{11}\hspace{0.17em}\exp \text{(−300/T),\hspace{0.17em}300−2000\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log \text{\hspace{0.17em}k±.3}\\ k_3{\mathrm{/k}}_2\text{=73\hspace{0.17em}}\exp \text{(2300/T),\hspace{0.17em}300−2000\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log {\mathrm{\hspace{0.17em}k}}_3{\mathrm{/k}}_2\text{±.3}\\ k_3{\text{=3.8×10}}^{13}\hspace{0.17em}\exp \text{(−2600/T),\hspace{0.17em}300−2000\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log \text{\hspace{0.17em}k±.3}\\ k_4{\mathrm{/k}}_2\text{=92\hspace{0.17em}}\exp \text{(2200/T),\hspace{0.17em}300−2000\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log {\mathrm{\hspace{0.17em}k}}_3{\mathrm{/k}}_2\text{±.3}\\ k_4{\text{=2.85×10}}^{13}\hspace{0.17em}\exp \text{(−2500/T),\hspace{0.17em}300−2000\hspace{0.17em}}\mathrm{K}\mathrm{,\hspace{0.17em}}\log \text{\hspace{0.17em}k±.7.}\end{array}$ Rate expressions are also recommended for a number of other hydroxyl reactions whose rates are less well established.