“…However, for thermal bromination, if concentrations are adjusted such that k propagation is the desired k Br for hydrogen atom abstraction, then k exp = k Br [K(Br 2 )] 1/2 where K(Br 2 ) is the known dissociation constant for Br 2 . In this way, absolute measurements of k Br have been reported for ethane, 1,1,1-trichloroethane, acetone, methanol, 1,1,1,2,3,3,3-heptafloropropane, pentafluoroethane, fluoroform, chloroform, and bromoform . The VLPR technique, in which the Knudsen cell reactor operates as a “continuously stirred tank reactor” and the concentrations of Br• and RH are determined directly by mass spectrometry on the effusing beam, has been applied to diethyl ether and i -butane. , However, the A value from a temperature variation study is often modified from the experimental value by statistical mechanics considerations and hence the extrapolation to 298 K is affected.…”