The rate constant for the reaction of OH with HFC-245cb (CH3-CF2-CF3) was measured by the flash photolysis resonance fluorescence technique over the temperature range 287-370 K in order to ascertain its atmospheric lifetime. Given the potential for trace levels of olefinic impurities to introduce errors into results of the rate constant measurements for low reactivity HFCs, considerable emphasis was placed on HFC purification and on demonstrating the utility of vacuum UV spectroscopy as a sensitive tool for detecting olefinic impurities in HFC samples. Measurements were also made of the OH rate constants for CH2=CH-CF3, CH2=CF-CF3, and CF2=CF-CF3, over the temperature range 252-370 K, and for CF2=CF2 at 298 K. Absorption spectra for the four fluoroalkenes as well as for ethene and propene were obtained from 160 to 220 nm.