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Kinetics of the gas‐phase reactions of cyclo‐CF 2 CFXCHXCHX – (X = H, F, Cl) with OH radicals at 253–328 K
Author(s) -
Chen L.,
Uchimaru T.,
Mizukado J.,
Kutsuna S.,
Tokuhashi K.,
Sekiya A.
Publication year - 2009
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.20431
Subject(s) - chemistry , reaction rate constant , radical , photodissociation , cyclobutane , reactivity (psychology) , cyclobutanes , kinetics , analytical chemistry (journal) , ozone , gas phase , photochemistry , organic chemistry , medicine , ring (chemistry) , alternative medicine , physics , pathology , quantum mechanics
Rate constants were determined for the reactions of OH radicals with halogenated cyclobutanes cyclo‐CF 2 CF 2 CHFCH 2 ( k 1 ), trans ‐cyclo‐CF 2 CF 2 CHClCHF( k 2 ), cyclo‐CF 2 CFClCH 2 CH 2 ( k 3 ), trans ‐cyclo‐CF 2 CFClCHClCH 2 ( k 4 ), and cis ‐cyclo‐CF 2 CFClCHClCH 2 ( k 5 ) by using a relative rate method. OH radicals were prepared by photolysis of ozone at a UV wavelength (254 nm) in 200 Torr of a sample reference H 2 OO 3 O 2 He gas mixture in an 11.5‐dm 3 temperature‐controlled reaction chamber. Rate constants of k 1 = (5.52 ± 1.32) × 10 −13 exp[–(1050 ± 70)/T], k 2 = (3.37 ± 0.88) × 10 −13 exp[–(850 ± 80)/T], k 3 = (9.54 ± 4.34) × 10 −13 exp[–(1000 ± 140)/T], k 4 = (5.47 ± 0.90) × 10 −13 exp[–(720 ± 50)/T], and k 5 = (5.21 ± 0.88) × 10 −13 exp[–(630 ± 50)/T] cm 3 molecule −1 s −1 were obtained at 253–328 K. The errors reported are ± 2 standard deviations, and represent precision only. Potential systematic errors associated with uncertainties in the reference rate constants could add an additional 10%–15% uncertainty to the uncertainty of k 1 – k 5 . The reactivity trends of these OH radical reactions were analyzed by using a collision theory–based kinetic equation. The rate constants k 1 – k 5 as well as those of related halogenated cyclobutane analogues were found to be strongly correlated with their CH bond dissociation enthalpies. We consider the dominant tropospheric loss process for the halogenated cyclobutanes studied here to be by reaction with the OH radicals, and atmospheric lifetimes of 3.2, 2.5, 1.5, 0.9, and 0.7 years are calculated for cyclo‐CF 2 CF 2 CHFCH 2 , trans ‐cyclo‐CF 2 CF 2 CHClCHF, cyclo‐CF 2 CFClCH 2 CH 2 , trans ‐cyclo‐CF 2 CFClCHClCH 2 , and cis ‐cyclo‐CF 2 CFClCHClCH 2 , respectively, by scaling from the lifetime of CH 3 CCl 3 . © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 532–542, 2009