Reactivity of 1,3- And 1,4-cyclohexadiene with OH radicals

Cyclohexadienes (CHD) are important intermediates in the pyrolysis and oxidation of many C6 cyclic hydrocarbons. These dienes either eliminate H2 directly or lose H-atom sequentially to produce the first aromatic ring “benzene”. This is the major reaction pathway for the formation of the first aromatic ring during pyrolysis and oxidation of C6 cyclic hydrocarbons. Despite its importance in the soot formation process, the chemistry of CHD has attracted less attention from the scientific community. In this work, we investigated the hydrogen abstraction reactions of 1,3- and 1,4-CHD by OH radicals using a shock tube and laser diagnostic techniques over the temperature range of 900 - 1300 K and pressures of ~ 1 and 4 atm. The reaction kinetics were followed by monitoring OH radicals near 307 nm. The measured rate coefficients for both CHD isomers with OH radicals can be represented by the following Arrhenius expressions in units of cm³ molecule^-1 s^-1: _"(1,3 ? CHD + OH) = 9.03 × 10^1"" exp 5?1360 ⁷₈9:(1,4 ? CHD + OH) = 1.21 × 10^1"= exp 5?1475 ⁷₈9.