KINETICS OF THE REACTIONS OF CH2(X)OVER-TILDE(3)B1) WITH SELECTED POLYCYCLIC AROMATIC-HYDROCARBONS AT TEMPERATURES BETWEEN 296-K AND 690-K

The kinetics of the reactions of CH2 radicals in their X3B1 ground ele ctronic state with the aromatic hydrocarbon molecules benzene (1), nap hthalene (2), phenanthrene (3), anthracene (4), and biphenyl (5) have been studied. Experimental measurements were carried out for reactions 2 - 5 at temperatures between 445 and 690 K using an isothermal disch arge flow system with far-infrared laser magnetic resonance (FIR-LMR) detection of the CH2 radicals. The results of these investigations as well as those of an earlier study of the rate constant of reaction 1 i n the temperature range 296 K less-than-or-equal-to T less-than-or-equ al-to 683 K were analyzed in light of recent temperature-dependent dat a on the competing reactions of CH2(a1A1). The direct experimental dat a for reactions 2-5 were found to be described by the following rate e xpressions (+/-2sigma): k2,exp = (2.5(+0.6/-0.5)) X 10(13) exp[-(30.0 +/- 0.9) kJ-mol-1/RT] cm3/(mol.s) (445 K less-than-or-equal-to T less- than-or-equal-to 660 K), k3,exp = (3.6(+4.8/-2.1)) X 10(13) exp[-(29.9 +/- 3.6) kJ-mol-1/RT] cm3/(mol.s) (477 K less-than-or-equal-to T less -than-or-equal-to 548 K), k4,exp = (8.5(+4.0/-2.7)) X 10(12) exp[-(17. 8 +/- 1.0) kJ-mol-1/RT] CM3/(mol.s) (523 K less-than-or-equal-to T les s-than-or-equal-to 690 K), and k5,exp = (2.9(+1.9/-1.2)) X 10(13) exp[ -(30.8 +/- 2.4) kJ-mol-1/RT] cm3/(mol.s) (476 K less-than-or-equal-to T less-than-or-equal-to 638 K). After correction for the depletion of CH2(-X) via excitation to the a state, the rate constants for the reac tive channels of CH2(X) (+/-2sigma) with the rive aromatics (1-5) were found to be k1T = (1.7(+1.2/-0.7)) X 10(13) exp[-(36.4 +/- 2.5) kJ.mo l-1 RT] cm3/(mol.s) (296 K less-than-or-equal-to T less-than-or-equal- to 683 K), k2T = (1.2(+0.3/-0.20) X 10(13) exp[-(27.7 +/- 1.0) kJ.mol- 1/RT] cm3/(mol.s) (445 K less-than-or-equal-to T less-than-or-equal-to 660 K), k3T = (2.2(+3.4/-1.4)) X 10(13) exp[-(28.5 +/- 3.9) kJ.mol-1/ RT] cm3/(mol.s) (477 K less-than-or-equal-to T less-than-or-equal-to 5 48 K), k4T = (6.2(+2.9/-2.0)) X 10(12) exp[-(16.6 +/- 1.9) kJ.mol-1/RT ] CM3/(mol.s) (523 K less-than-or-equal-to T less-than-or-equal-to 690 K), and k5T = (1.3(+1.1/-0.6)) X 10(13) exp[-(28.2 +/- 2.9) kJ.mol-1/ RT] cm3/(mol.s) (476 K less-than-or-equal-to T less-than-or-equal-to 6 38 K).