The equilibrium constants for the Z to E isomerizations of CF3CF=CHF (K-1) and CF3CH=CHCF3 (K-2) have been measured using GC/FID analysis over the temperature ranges 360-850 and 297-850 K, respectively. At lower temperature, K was determined using Cl atom catalysis. At higher temperature, K was measured without a catalyst. The temperature-dependent expressions are K1 (Z to E) = 1.45( +/- 0.15)-e (-[2845(+/- 100)/RT]) and K-2 (Z to E) = 1.9(+/- 0.22)e(+[4330(+/- 120/RT]) (where the gas constant R 1.986 cal mol(-1) K-1). For isomerization I, the Z (fluorine cis) isomer is 2.85 kcal mol(-1) lower in energy than the E (fluorine trans) isomer, providing another example of the fluorine "cis effect" in olefins. For isomerization 2, the E(trans) isomer is 4.3 kcal mol(-1) lower in energy than the corresponding Z(cis) isomer as is normal for olefins. The isomerization rate constant in a single direction was also measured for each fluorinated compound: k(-1)(E to Z) = 10(13.87 +/- 0.24)e(-59530(+/- 887)/RT) s(-1); and k(2)(Z to E) = 10(13.89 +/- 0.23)e(-58845(+/- 675)/RT) s(-1). To verify the experimental method, cis to trans (k(3)) and trans to cis (k(-3)) isomerization rate constants were also measured for cis- and trans-2-butene for comparison to several previous studies. The rate constants determined herein are k3 (cis to trans) = 10(13.95 +/- 0.23)e(-63245()+/- 815)/RT s(-1). and k(-3) (trans to cis) k3 agrees well with four previous measurements and represents the best available rate constant for 2-butene. All errors quoted here are 2 sigma. The typical total pressure for these experiments was 760 +/- 100 Torr. Limited experiments performed at 100 Torr showed no pressure dependence for any of the compounds above 100 Torr. Thus, all isomerization rate constants represent high-pressure limits. The rates of the addition reactions of Cl to the double bonds of CF3CF=CHF (k(4)) and CF3CH=CHCF3 (k(7)) (used in Cl catalysis) were also measured in pure N-2 and in pure O-2. In O-2, the rate constants expressions are k(4) = 1.56 (+/- 0.22) X 10(-11) e(+(643/RT)) cm(3) molecule(-1) s(-1); and k(7) = 1.05 X 10(-12) e(+(1874/RT)) cm(3) molecule(-1) s-(1). In N-2, k(4) and k(7) decrease several orders of magnitude as the temperature increases because of the increasing reversibility of the Cl addition reaction, which produces the catalytic effect.