Rate coefficients for the reaction of methylglyoxal (CH3COCHO) with OH and NO3 and glyoxal (HCO)2 with NO3

R. K. Talukdar, L. Zhu, K. J. Feierabend, J. B. Burkholder
2011 Atmospheric Chemistry and Physics  
<p><strong>Abstract.</strong> Rate coefficients, <i>k</i>, for the gas-phase reaction of CH<sub>3</sub>COCHO (methylglyoxal) with the OH and NO<sub>3</sub> radicals and (CHO)<sub>2</sub> (glyoxal) with the NO<sub>3</sub> radical are reported. Rate coefficients for the OH + CH<sub>3</sub>COCHO (<i>k</i><sub>1</sub>) reaction were measured under pseudo-first-order conditions in OH as a function of temperature (211–373 K) and pressure (100–220 Torr, He and N<sub>2</sub> bath gases) using pulsed
more » ... er photolysis to produce OH radicals and laser induced fluorescence to measure its temporal profile. <i>k</i><sub>1</sub> was found to be independent of the bath gas pressure with <i>k</i><sub>1</sub>(295 K) = (1.29 &amp;plusmn; 0.13) &amp;times; 10<sup>&amp;minus;11</sup> cm<sup>3</sup> molecule<sup>&amp;minus;1</sup> s<sup>&amp;minus;1</sup> and a temperature dependence that is well represented by the Arrhenius expression <i>k</i><sub>1</sub>(<i>T</i>) = (1.74 &amp;plusmn; 0.20) &amp;times; 10<sup>&amp;minus;12</sup> exp[(590 &amp;plusmn; 40)/<i>T</i>] cm<sup>3</sup> molecule<sup>&amp;minus;1</sup> s<sup>&amp;minus;1</sup> where the uncertainties are 2&amp;sigma; and include estimated systematic errors. Rate coefficients for the NO<sub>3</sub> + (CHO)<sub>2</sub> (<i>k</i><sub>3</sub>) and NO<sub>3</sub> + CH<sub>3</sub>COCHO (<i>k</i><sub>4</sub>) reactions were measured using a relative rate technique to be <i>k</i><sub>3</sub>(296 K) = (4.0 &amp;plusmn; 1.0) &amp;times; 10<sup>&amp;minus;16</sup> cm<sup>3</sup> molecule<sup>&amp;minus;1</sup> s<sup>&amp;minus;1</sup> and <i>k</i><sub>4</sub>(296 K) = (5.1 &amp;plusmn; 2.1) &amp;times; 10<sup>&amp;minus;16</sup> cm<sup>3</sup> molecule<sup>&amp;minus;1</sup> s<sup>&amp;minus;1</sup>. <i>k</i><sub>3</sub>(<i>T</i>) was also measured using an absolute rate coefficient method under pseudo-first-order conditions at 296 and 353 K to be (4.2 &amp;plusmn; 0.8) &amp;times; 10<sup>&amp;minus;16</sup> and (7.9 &amp;plusmn; 3.6) &amp;times; 10<sup>&amp;minus;16</sup> cm<sup>3</sup> molecule<sup>&amp;minus;1</sup> s<sup>&amp;minus;1</sup>, respectively, in agreement with the relative rate result obtained at room temperature. The atmospheric implications of the OH and NO<sub>3</sub> reaction rate coefficients measured in this work are discussed.</p>
doi:10.5194/acp-11-10837-2011 fatcat:hfng3jfz5bgudlgw3u3jin7uve