Competitive study of the reactions Br + RFI → IBr + RF and determination of bond dissociation energies D(RF−I) where RF = CF3, C2F5, n-;C3F7, i-C3F7, and n-C4F9

The overall photobromination reactions have been studied using a competitive technique. Relative Arrhenius parameters were obtained for the rate-determining step These were placed on an absolute basis using previous-absolute values of A and E for R_FI=CF₃I. The activation energies were used to calculate bond dissociation energies D(R? I) with the following results:

RF?	E16	D(RF?I)(kcal/mole)
CF3I a a E16 from 1]	10.8	52.6
C2F5I	8.8	50.6
n-C3F7I	7.4	49.2
i-C3F7I	7.5	49.2
n-C4F9I	6.7	48.4

• ^a E₁₆ from 1]

The D(RI) are compared with related D(R? I) and it is concluded that for a given alkyl group R_H and the corresponding perfuloroalkyl group R_F, D(RI) > D(RI) whereas it has previously been found that D(RX;) < D(RX) where X is not iodine.