ATMOSPHERIC CHEMISTRY OF HFC-272CA - SPECTROKINETIC INVESTIGATION OF THE CH3CF2CH2O2 RADICAL, ITS REACTIONS WITH NO AND NO2, AND THE FATE OF THE CH3CF2CH2O RADICAL

A pulse radiolysis technique has been used to investigate the UV absor ption spectrum of the CH3CF2CH2O2 radical from HFC-272ca, CH3CF2CH3. T he absorption cross sections were quantified in the wavelength range 2 20-320 nm; at 250 nm the absorption cross section for CH3CF3CH2O2 was sigma = (451 +/- 59) x 10(-20) cm(2) molecule(-1). By following the in crease in NO2 at 400 nm, the rate constant for the reaction of CH3CF2C H2O2 with NO was determined to be (8.5 +/- 1.9) x 10(-12) cm(3) molecu le(-1) s(-1). The reaction of CH3CF2CH2O2 with NO2 was found to have a reaction rate constant of (6.8 +/- 0.5) x 10(-12) cm(3) molecule(-1) s(-1). The kinetics of the reaction of CH3CF2CH3 with F atoms and CH3C F2CH2 with O-2 were studied. The rate constants were (2.8 +/- 0.9) x 1 0(-11) and (1.10 +/- 0.03) x 10(-12) cm(3) molecule(-1) s(-1), respect ively. The observed rate constant for the self-reaction of CH3CF2CH2O2 radicals was (8.6 +/- 0.4) x 10(-12) cm(3) molecule(-1) s(-1). The re action of CH3CF2CH2O2 radicals with NO gives CH3CF2CH2O radicals; the dominant atmospheric fate of CH3CF2CH2O radicals is reaction with O-2 to give CH3CF2CHO. As part of the present work, relative rate techniqu es were used to measure rate constants at 296 +/- 2 K for the reaction s of Cl and F atoms with CH3CF2CH3, with the values being (1.7 +/- 0.2 ) x 10(-14) and (3.3 +/- 0.8) x 10(-11) cm(3) molecule(-1) s(-1), resp ectively.