Arrhenius parameters for reactions of oxygen atoms with the fluorinated ethylenes

Competitive studies of the reactions of ground-state oxygen atoms, generated by mercury-photosensitized decomposition of nitrous oxide, have been carried out with ethylene and all the fluoroethylenes using 2-(trifluoromethyl)-propene as reference compound. From measurements at 25°C and 150°C relative rate constants have been determined and used to calculate the Arrhenius parameters shown in the following table:

Olefin		ΔERef		ΔE
CH2? CH2	1.10	?1.18	(1.0)	(0)
CH2? CHF	1.03	0.84	0.94	2.02
CH2? CF2	0.71	1.49	0.65	2.67
CHF? CHF (cis-)	1.23	1.92	1.12	3.10
CHF? CHF (trans-)	1.40	0.79	1.27	1.97
CF2? CHF	1.06	0.00	0.96	1.22
CF2? CF2	0.86	?3.22	0.78	?2.04

• ^a ΔE_Ref = E_olefin ? E_2TFMP and ΔE = E_olefin ? E. Units are kJ/mole.

The results are compared with corresponding data for other atoms and radicals, and discussed in terms of the electronic changes produced in the double bond by fluorine substitution, and in relation to the nature of the transition state.