TY - JOUR
T1 - Atmospheric chemistry of HFC-236cb
T2 - Fate of the alkoxy radical CF3CF2CFHO
AU - Møgelberg, Trine E.
AU - Sehested, Jens
AU - Tyndall, Geoffrey S.
AU - Orlando, John J.
AU - Fracheboud, Jean Marc
AU - Wallington, Timothy J.
PY - 1997/4/10
Y1 - 1997/4/10
N2 - An FTIR/environmental chamber technique was used to study the fate of the alkoxy radical CF3CF2CFHO formed in the atmospheric degradation of HFC-236cb (CF3CF2CFH2). Experiments were performed over the temperature range 228-296 K at 7.8-1000 Torr total pressure. Two reaction pathways are possible for CF3CF2CFHO radicals: reaction with oxygen, CF3CF2CFHO + O2 → CF3CF2C(O)F + HO2 (kO2) and decomposition via C-C bond scission, CF3CF2CFHO → CF3CF2 + HC(O)F (kd). CF3CF2CFHO radicals were produced by two reactions: the CF3CF2CFHO2 self-reaction and the CF3CF2CFHO2 + NO reaction. In the absence of NO at 800 Torr total pressure the rate constant ratio kd/kO2 was determined to be (6.6+16.3-4.7) × 1025 exp(-(3560 ± 295)/T) molecules cm-3. The pressure dependence of kd/kO2 was studied at 238 K and was well described by a Troe type expression using kd,0/kO2 = 30.8 ± 6.9 and kd,∞/kO2 = (2.31 ± 0.12) × 1019 molecules cm-3 where kd,∞ and kd,∞ are the second- and first-order rate constants for decomposition in the low- and high-pressure limits, respectively. CF3CF2CFHO radicals formed in the CF3CF2CFHO2 + NO reaction undergo more C-C bond scission than those generated in the CF3CF2CFHO2 self-reaction. This is consistent with a significant fraction (67+19-22%) of the alkoxy radicals being formed with sufficient internal energy to undergo prompt decomposition. Overall, we calculate that less than 1% of the CF3CF2CFH2 (HFC-236cb) released to the atmosphere degrades to form CF3CF2C(O)F while >99% gives CF3CF2 radicals and HC(O)F.
AB - An FTIR/environmental chamber technique was used to study the fate of the alkoxy radical CF3CF2CFHO formed in the atmospheric degradation of HFC-236cb (CF3CF2CFH2). Experiments were performed over the temperature range 228-296 K at 7.8-1000 Torr total pressure. Two reaction pathways are possible for CF3CF2CFHO radicals: reaction with oxygen, CF3CF2CFHO + O2 → CF3CF2C(O)F + HO2 (kO2) and decomposition via C-C bond scission, CF3CF2CFHO → CF3CF2 + HC(O)F (kd). CF3CF2CFHO radicals were produced by two reactions: the CF3CF2CFHO2 self-reaction and the CF3CF2CFHO2 + NO reaction. In the absence of NO at 800 Torr total pressure the rate constant ratio kd/kO2 was determined to be (6.6+16.3-4.7) × 1025 exp(-(3560 ± 295)/T) molecules cm-3. The pressure dependence of kd/kO2 was studied at 238 K and was well described by a Troe type expression using kd,0/kO2 = 30.8 ± 6.9 and kd,∞/kO2 = (2.31 ± 0.12) × 1019 molecules cm-3 where kd,∞ and kd,∞ are the second- and first-order rate constants for decomposition in the low- and high-pressure limits, respectively. CF3CF2CFHO radicals formed in the CF3CF2CFHO2 + NO reaction undergo more C-C bond scission than those generated in the CF3CF2CFHO2 self-reaction. This is consistent with a significant fraction (67+19-22%) of the alkoxy radicals being formed with sufficient internal energy to undergo prompt decomposition. Overall, we calculate that less than 1% of the CF3CF2CFH2 (HFC-236cb) released to the atmosphere degrades to form CF3CF2C(O)F while >99% gives CF3CF2 radicals and HC(O)F.
UR - https://www.scopus.com/pages/publications/0001170811
U2 - 10.1021/jp963021h
DO - 10.1021/jp963021h
M3 - Article
AN - SCOPUS:0001170811
SN - 1089-5639
VL - 101
SP - 2828
EP - 2832
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 15
ER -