Competition Kinetics of the Nonbranched-Chain Addition of Free Radicals to Olefins, Formaldehyde, and Oxygen

Scheme 4

Nonbranched-chain oxidation of hydrogen and changes in enthalpy (Δ𝐻^∘298, kJ mol⁻¹) for elementary reactions.⁹

Chain initiation:

(1) H−−−→_{2ℎ𝜈,𝛾}2H^•,            ΔH^∘298=436.0±0.0.

Chain propagation:

(2) H^•+O−→_2𝑘²HO^•2,         ΔH^∘298=−205.4±1.7;

(3) HO^•2+H−→_2𝑘³H₂O+HO^•,      ΔH^∘298=−215.4±2.9;

      (orH₂O₂+H^•),      ΔH^∘298=69.4±1.7;

(3′) HO^•+H−−→_2𝑘^3′H₂O+H^•,      ΔH^∘298=−62.8±1.2.

Inhibition:

(4) HO^•2+O−→_2𝑘⁴HO^•4,         ΔH^∘298=110.0±15.4.

Chain termination:

(5) 2H^•(+M)−−→^2𝑘5H₂(+M),       ΔH^∘298=−436.0±0.0;

(6) H^•+HO−→^•4𝑘6H₂O₂+O₂,      ΔH^∘298=−476.6±13.7,

      (or∶H₂O+O₃,    ΔH^∘298=−439.3±15.4,

        H₂+2O₂),    ΔH^∘298=−340.6±13.7;

(7) 2HO−−→^•42𝑘7H₂O₂+3O₂,      ΔH^∘298=−381.2±27.4,

     (or:H₂O+O₃+2O₂,    ΔH^∘298=−343.9±29.1,

       H₂O₂+2O₃,    ΔH^∘298=−95.0±30.8,

       H₂+4O₂),    ΔH^∘298=−245.2±27.4