Rate constants for the reactions of hydroxyl radicals (OH) with 1,1,1,3,3,3hexafluoroisopropyl methyl ether (CH3-O-CH(CF3)2) and 4-bromo-3-chloro-3,4,4-trifluoro-1butene (CH2HCH-CFCl-CF2Br) have been measured over the temperature range 230−370 K to give the following Arrhenius expressions: kCH3OCH(CF3)2(T) = 7.69 × 10−14 × (T/298)2.99 × exp(+342/T), cm3 molecule−1 s−1, and kCH2CHCFClCF2Br(T) = (6.45 ± 0.72) × 10−13 × exp{+(424 ± 32)/T}, cm3 molecule−1 s−1. Atmospheric lifetimes of compounds were estimated to be 67 days and 4.5 days, respectively. UV absorption spectrum of CH2HCH-CFCl-CF2Br between 164 and 260 nm and IR absorption spectra of both compounds between 450 and 1600 cm−1 were measured at room temperature.