Ethyl chloride, transference experiments

Transference experiments furnish evidence for equation 19. Ethyl chloride and ethyl bromide are nonconductors, but when the corresponding aluminum halide is introduced, the solutions can be electrolyzed and aluminum becomes concentrated in the anode compartment.5... 

Reaction 9 shows that the major portion of the reacting ethylene ions interact with ethyl chloride by discrete transfer steps including H" transfer, H2" transfer, and possibly Cl" transfer. Also, as discussed later, the total cross section for reaction of ethylene ions in this system is quite large (> 100 sq. A.). This may be compared with the corresponding reaction of ethylene ions with ethane, for which extremely small cross-sections have been found (44). In the latter case, however, the H" transfer reaction is endothermic, and the H2" transfer process would not have been detected in the previous experiments. These facts may explain the low reactivity reported. With ethyl chloride, H" transfer to ethylene ions is also indicated to be endothermic by the usual calculations. This suggests that the reactant ethylene ions in this system may well be vibra-tionally excited. It would also account for the chloride ion transfer to this ion, mentioned above. The ratio of rate constants observed for C2H4+ reaction with ethyl chloride is kU2-/ku- = 1.4. In addition to the reactions just discussed, part of the ethylene ion reactant forms a complex intermediate with CoH5C1, and elimination of HC1 and DC1 from this intermediate occurs with about equal probability. 

Based on experience, the following procedure was suggested for the preparation of TFA-amyl esters of amino acids. A sample of amino acids (0.5—2 mg of each acid) was placed into a test-tube and dissolved in 0.2 ml of trifluoroacetic acid. Amyl alcohol (2 ml) was added and dry hydrogen chloride was bubbled through the reaction mixture continuously at 108°C for 25 min. Excess of the reagent was removed under vacuum, dissolved in a small amount of methanol, transferred into a small test-tube and the methanol was evaporated by standing freely at 70°C. TFA anhydride (1 ml) was added and the stoppered test-tube was allowed to stand at room temperature for 1 h. As some of the amino acids (e.g., Arg) were not acylated quantitatively by this procedure, it was recommended that the sealed test-tube be heated at 140°C for 5 min [229]. Excess of anhydride was removed under vacuum and the residue was dissolved in a known volume of dry methyl ethyl ketone. 

The interaction term is in brackets, and for this case is independent of [Si]. In the methyl chloride-ethyl bromide system such an independence is found—e.g., for the four runs at ethyl bromide concentration of 0.1M, ratios observed for G(P)S2obs/G(P)s2caic (— /([Si],[S2] )exp) are 0.74, 0.76, 0.67, and 0.72. From a ratio of 0.72 at 0.1 Af C2HsBr, ft is evaluated as 1.51 (assuming of course the form of /( [Si],[S2] )). From this the individual yields may be calculated for the other experiments and are the unbracketed values in Table VI. The available data are well described by Equation XX. Using Equation XX and an analogous expression for G (Q)Sl one can show that where electron transfer occurs from... 

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