Reaction of HO with hydroxyacetone (HOCH2C(O)CH3):: rate coefficients (233-363 K) and mechanism

Absolute rate coefficients for the title reaction, HO + HOCH2C(O)CH3 -> products (R1) were measured over the temperature range 233-363 K using the technique of pulsed laser photolytic generation of the HO radical coupled to detection by pulsed laser induced fluorescence. The rate coefficient displays a slight negative temperature dependence, which is described by: k(1)(233-363 K) = (2.15 +/- 0.30) x 10(-12) exp{(305 +/- 10)/T} cm(3) molecule(-1) s(-1), with a value of (5.95 +/- 0.50) X 10(-12) cm(3) molecule(-1) s(-1) at room temperature. The effects of the hydroxy-substituent and hydrogen bonding on the rate coefficient are discussed based on theoretical calculations. The present results, which extend the database on the title reaction to a range of temperatures, indicate that RI is the dominant loss process for hydroxyacetone throughout the troposphere, resulting in formation of methylglyoxal at all atmospheric temperatures. As part of this work, the rate coefficient for reaction of O(P-3) with HOCH2C(O)CH3 (R4) was measured at 358 K: k(4)(358 K) = (6.4 +/- 1.0) x 10(-14) cm(3) molecule(-1) s(-1) and the absorption cross section of HOCH2C(O)CH3 at 184.9 nm was determined to be (5.4 +/- 10.1) x 10(-18) cm(2) molecule(-1).