Reaction and complex formation between OH radical and acetone

Abstract

Kinetics and mechanism of the reaction of OH with have been studied by discharge-Ñow CH 3 C(O)CH

The reaction of OH with acetone and acetone-d6 from 298 to 832 K: Rate coefficients and mechanism

“…Vasvári et al argued for OH abstraction from C-H bonds via a transition state ͑TS͒ in the plane of the carbon atoms, or addition to the central carbon atom normal to this plane, with weakly bound adducts at the entrances of both paths. 6 They commented that the high barrier they found for formation of a covalently bound adduct was inconsistent with their observations, and that a new unidentified mechanism might operate at low temperatures. Vandenberk et al presented a qualitatively different potential energy surface, with channels for addition, direct abstraction and abstraction via a hydrogenbonded intermediate.…”

“…All experiments were conducted at a total pressure of 735Ϯ10 torr with helium as the bath gas. High purity samples ͑Ͼ99.9%͒ of acetone and acetone-d 6 were obtained from Aldrich, Inc. and used as received, and GC/MS analyses indicated the absence of any reactive impurities that would impact the rate measurements. Analysis of the reactor gas stream showed that HONO generation did not produce detectable concentrations of potentially interfering NO, NO 2 or HCl (Ͻ1.2ϫ10 12 molecule cm Ϫ3 ).…”

“…They later determined yields of CH 3 , a likely product of an addition/elimination channel also producing acetic acid, to be 50% and 30% at 298 and 200 K, respectively, 10 consistent with less addition at lower temperatures. Vasvári et al measured a 50% yield of acetonyl, the H-abstraction product, at 298 K. 6 By contrast, Vandenberk et al 11 and Tyndall et al 1 found no evidence for acetic acid formation ͑upper limits of 3% and 10%, respectively͒ at room temperature. Talukdar et al very recently published an even lower limit for acetic acid formation, below 1%, and reported a 96%Ϯ11% yield of acetonyl.…”

“…1, [2][3][4][5][6][7][8][9] and it may be seen that while different experiments have yielded different activation energies, overall there is good agreement between the magnitude of the k values. There is an unusual temperature dependence, with k increasing with T above room temperature, and decreasing much more slowly, or perhaps even increasing slightly, at lower temperatures.…”

Rate constant for the reaction of OH radicals with CH3C(O)Cl determined by direct kinetic method

“…This observation is in accordance with the known electrophilic behavior of the hydroxyl radical in its elementary reactions. k 1 is about five times smaller than the rate constant of OH with acetone given for one methyl group, i. e., (1/2) x k(OH + CH 3 C(O)CH 3 ) = 5.2 x 10 10 cm 3 mol -1 s -1 (T = 298 K) [6].…”