RATE CONSTANTS FOR THE REACTIONS OF CH2((X)OVER-TILDE3B1) WITH SELECTED ALKENES AT TEMPERATURES BETWEEN 296-K LESS-THAN-OR-EQUAL-TO T LESS-THAN-OR-EQUAL-TO 728-K

The kinetics of the reactions of CH2(X3B1) with selected alkenes R = e thylene (1), tetramethylethylene (2), cycloheptatriene (3), and 1,3-bu tadiene (4) were studied at temperatures between 296 K less-than-or-eq ual-to T less-than-or-equal-to 728 K. Rate constants were measured for reactions (2-4) using the discharge flow technique with Far-Infrared Laser Magnetic Resonance (FIR-LMR) detection of (CH2)-C-3. The experim ental data can be described by the rate expressions (+/-2sigma) k2,exp = .6(+0.9/-0.6)).10(13)exp[-(26.2+/-2.0)kJ.mol-1/RT] cm3/mol.s, (475 K less-than-or-equal-to T less-than-or-equal-to 663 K), k2,exp = .9(+2 .3/-2.0)).10(12)exp[-(20.4+/-1.0)kJ.mol-1/RT] cm3/mol.s, (438 K less-t han-or-equal-to T less-than-or-equal-to 638 K), k4,exp = .3(+1.0/-0.8) ).10(12)exp[-(14.9+/-0.6)kJ.mol-1/RT] cm3/mol.s, (296 K less-than-or-e qual-to T less-than-or-equal-to 700 K). These data and results for rea ction (1) obtained earlier were analyzed to separate the contributions to the CH2(X) depletion by reactive channels versus collisional excit ation to the a 1A1 state of CH2 followed by reactions of CH2(a). The r ate expressions (+/-2sigma) for the reactive pathways of CH2(X) were f ound to be k1,T = .8)).10(12)exp[-(22.1+/-1.1)kJ.mol-1/RT]cm3/mol.s, ( 296 K less-than-or-equal-to T less-than-or-equal-to 728 K), k2,T = .7) ).10(12)exp[-(24.1+/-2.6)kJ.mol-1/RT]cm3/mol.s, (475 K less-than-or-eq ual-to T less-than-or-equal-to 663 K), k3,T = .3)).10(12)exp[-(19.0+/- 1.0)kJ.mol-1/RT]cm3/mol.s, (438 K less-than-or-equal-to T less-than-or -equal-to 638 K), k4,T = .8)).10(12)exp[-(14.4+/-0.6)kJ.mol-1/RT]cm3/m ol.s, (296 K less-than-or-equal-to T less-than-or-equal-to 700 K).