THE TEMPERATURE-DEPENDENCE OF THE RATE COEFFICIENTS FOR BETA-HYDROXYPEROXY RADICAL SELF REACTIONS

A laser-flash photolysis/UV absorption technique has been used to stud y the temperature dependence (from T = 300-470 K) of the self-reaction kinetics of representative primary, secondary, and tertiary beta-hydr oxyperoxy radicals: [GRAPHICS] The following Arrhenius expressions wer e derived for the rate coefficients of reactions (1)-(3) (in cm(3)mole cule(-1)s(-1)) and for the product branching ratios of reactions (1) a nd (2) as a function of temperature (all errors 1 sigma): k(1) = (6.9( +2.1)(-1.5)) x 10(-14) exp[(1040 +/- 100)/T] beta(1) = (3100(+3700)(-1 700)) exp[(-2400 +/- 280)/T] (where beta(1) = k(1a)/k(1b)) k(2) = (7.7 (+12.8)(-4.8)) x 10(-15) exp[(1330 +/- 350)/T] beta(2) = (40(+0.2)(-0. 1)) x 10(4) exp[(-3600 +/- 100)/T] k(3) = (4.7(+6.5)(-2.7)) x 10(-13) exp[(-1420 +/- 320)/T] The calculated rate coefficients for reactions (1)-(3) at 298 K are therefore (in 10(-13) cm(3)molecule(-1)s(-1)) 23 +/- 2, 6.7 +/- 1.3, and 0.040 +/- 0.012, respectively, which compare w ell with the values measured elsewhere at this temperature using a sim ilar technique. The product branching ratios and the Arrhenius paramet ers are compared with those for other substituted and unsubstituted pe roxy radical self reactions. (C) 1997 John Wiley & Sons, Inc.