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Atmospheric Chemistry of CH 3 OCF 2 CHF 2 .

Authors :: Kjærgaard ER
Vogt E
Møller KH
Nielsen OJ
Kjaergaard HG
Source :: The journal of physical chemistry. A [J Phys Chem A] 2021 Dec 23; Vol. 125 (50), pp. 10640-10648. Date of Electronic Publication: 2021 Dec 14.
Publication Year :: 2021
Abstract: Fourier transform infrared spectroscopy has been used to follow the reaction of CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> with either Cl or OH radicals within a photoreactor. Rate constants of k (OH + CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> ) = (2.25 ± 0.60) × 10 <superscript>-14</superscript> cm <superscript>3</superscript> molecule <superscript>-1</superscript> s <superscript>-1</superscript> and k (Cl + CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> ) = (2.50 ± 0.39) × 10 <superscript>-13</superscript> cm <superscript>3</superscript> molecule <superscript>-1</superscript> s <superscript>-1</superscript> were determined at 296 ± 2 K. Theoretical and experimental investigation of the Cl + CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> reaction identified the formation of two main products, HC(O)OCF <subscript>2</subscript> CHF <subscript>2</subscript> and COF <subscript>2</subscript> . Chlorine (and OH) radicals react with CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> by H-abstraction from either the -CH <subscript>3</subscript> or -CHF <subscript>2</subscript> site. Abstraction from the -CH <subscript>3</subscript> site was determined to constitute at least 60%, as determined from the formation of the primary product, HC(O)OCF <subscript>2</subscript> CHF <subscript>2</subscript> , which can only form from this abstraction site. At longer reaction times, HC(O)OCF <subscript>2</subscript> CHF <subscript>2</subscript> further reacts and the yield of COF <subscript>2</subscript> approaches two, the maximum possible with the number of F atoms in the reactant. The atmospheric lifetime of CH <subscript>3</subscript> OCF <subscript>2</subscript> CHF <subscript>2</subscript> with OH radicals was determined to be 1.4 years. The global warming potentials over 20-, 100-, and 500-year time horizons were estimated to be 325, 88, and 25, respectively.