Rate coefficients for the reaction CH3 + Oz = CH3O + O were measured behind
reflected shock waves in a series of lean CH4-O-2-Ar mixtures using hydrox
yl and methyl radical diagnostics. The rate coefficients are well represent
ed by an Arrhenius expression given as k = (1.60(-0.47)(+0.67)) x 10(13) ex
p(-15813 +/- 587 K/T) cm(3) mol(-1) s(-1). This expression, which is valid
in the temperature range 1575-1822 K, supports the downward trend in the ra
te coefficients that has been reported in recent determinations. All measur
ements to date, including the present study, have been to some extent affec
ted by secondary reactions. The complications due to secondary reactions, c
hoice of thermochemical data, and shock-boundary layer interactions that af
fect the determination of the rate coefficients are examined.