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The reactions of photochemically generated Cl(2PJ) atoms with a number of fluorohydrocarbons have been investigated in the temperature range 8–95 °C by the competitive photochlorination technique using CH4 as a primary standard. Relative and absolute rate parameters are reported for CH3F, CH2F2, CH3CH2F, CH2FCH2F, CH3CHF2, CH3CF3, CH2FCHF2, CHF2CHF2, and several auxiliary reactions including CH3Cl, C2H6, and C3H8. The internal competition for hydrogen abstraction in asymmetric fluorethanes is examined in detail. The reactivity trends are discussed and it is found that the activation energies in the fluoromethane series correlate with the known C–H bond dissociation energies. The hydrogen reactivity in the fluoroethane series for which a sufficient data base of DH°(C–H) values is not available is best rationalized in terms of inductive effects and resonance interactions.

The abstraction of hydrogen and deuterium from ethane, I, 1-dichloroethane, I , ] , 1-trichloroethane, and some of their deuterated analogs by photochemically generated ground state chlorine atoms has been investigated in the temperature range 7-95°C using methane as competitor. Rate constants and their temperature coefficients are reported for the following reactions:

The adsorption of water vapour in the sorbents used to sample volatile organic compounds (VOCs) from the atmosphere was investigated by frontal gas chromatography. Air of 95% relative humidity (RH) was passed through the sorbent bed and the uptake of water was monitored at the outlet of the trap. Graphitized carbons and non-polar polymeric sorbents, such as Tenax and Chromosorb 106, show poor water trapping of generally less than 5 mg of water per gram of sorbent. Polar polymeric sorbents, e.g. Chromosorb 108, Porapak T and Porapak N, sorb more water which is, however, weakly bound and easily removed by purging the sorbent bed with a dry gas. Carbon molecular sieves, e.g. Carbosieve S-III, Carboxen 569, Carboxen 1000 and Carboxen 1001, adsorb substantial amounts of water, corresponding to the volume of micropores. An important feature is a lack of adsorption at low RHs. Measures to prevent water adsorption in sampling even very humid gases are advanced. The RH of sampled gas should be decreased below a threshold value (RH thr ). The RH thr is 50% for Carboxen 1000 and less than that for the other sorbents studied. Practical implementation of the suggested method is discussed.

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