A Product Yield Study of the Reaction of HO_2 Radicals with Ethyl Peroxy (C_2H_5O_2),Acetyl Peroxy (CH_3C(O)O_2),and Acetonyl Peroxy (CH_3C(O)CH_2O_2) Radicals

摘要

The reaction between HO_2 and RO_2 radicals represents an important chemical sink for HO_x radicals in the atmosphere.On the basis of a few product yield studies,these reactions are believed to form hydroperoxides almost exclusively (R8a),although several different reaction channels may be thermodynamically accessible (R8a-d):RO_2+HO_2-ROOH+O_2 (R8a);RO_2+HO_2->ROH+O_3 (R8b);RO_2+HO_2->RO+OH+O_2 (R8c);and RO_2+HO_2->R'CHO+H_2O+O_2 (R8d).Branching ratios for reaction R8 were measured for three organic peroxy radicals:ethyl peroxy (C_2H_5O_2),acetyl peroxy (CH_3C(O)O_2),and acetonyl peroxy (CH_3C(O)CH_2O_2) radicals.Product yields were measured using a combination of long-path Fourier transform infrared spectroscopy and high-performance liquid chromatography with fluorescence detection.Measured branching ratios for the reaction of the three organic peroxy radicals with HO_2 are as follows:ethyl peroxy,Y_(8a)-ETH>0.93+-0.10,Y_(8b-ETH)=Y_(8c-ETH)=Y_(8d-ETH)=0;acetyl peroxy,Y_(8a-ACT=0.40+-0.16,Y_(8b-ACT)=0.20+-0.08,Y_(8c-ACT)=0.40+-0.16,and Y_(8d-ACT)=0;acetonyl peroxy,Y_(8a-ACN)=0.33+-0.10,Y_(8b-ACN)=Y_(8d-ACN)=0,and Y_(8c-ACN)=0.67+-0.20.The atmospheric implications of these branching ratios are discussed.