Ethyl chloride ions, decomposition

On the basis of previous discussion, the only additional source of ethylene in the radiolysis is the decomposition of excited neutral ethyl chloride molecules. If the ion-molecule contribution to this product is subtracted from the total yield reported in Table III, an ethylene-acetylene yield of G = 4.24 may be attributed to excited neutral decomposition. If we now assume that the photolysis experiments provide a direct measure of the neutral excited molecule decomposition to be expected in the radiolysis, this ethylene yield may be used as a basis for normalization to estimate the contributions from this source to the other products using the relative photolysis distributions from Table IV. In this way, the contributions from excited neutral decomposition reported in Table V were derived. 

The radiolysis product yields in the presence of ion scavenger (Table III) also show that ethane is not formed from neutralization of stable ions. Therefore, the remainder of the ethane product (above that indicated to result from neutral decomposition) must be produced by an ion-molecule process—i.e., a yield of G = 1.47. The ion-molecule reactions previously listed show that ethylene ions react with ethyl chloride to form ethane. From the relative rates indicated for Reactions 3a-3d and the ethane yield just derived, a relative yield of 2.46 may be deduced for the ionic fragmentation to ethylene ion in the radiolysis. 

Ionic reactions in ethyl chloride have been studied by both mass spectrometric and radiolysis techniques. The radiolysis mechanism advanced on the basis of our experimental observations indicates that the major radiolytic reaction mode in this system is excited neutral molecule decomposition. While the role of ionic reactions in the radiolysis therefore appears to be relatively minor, it was possible to establish a good correlation between the predictions of the mass spectrometric studies with respect to ionic intermediates and the participation of such ions in the radiolytic reaction scheme. These results emphasize the advantages of combining the techniques used here to obtain a complete description of the reactive system. 

It has been observed2 that the dropwise addition of an aqueous solution of potassium ethyl xanthate to a cold (0°) aqueous solution of diazotized orthanilic acid results in the immediate loss of nitrogen when a trace of nickel ion is present in the stirred diazonium solution.3 The catalyst can be added as nickelous chloride or simply by using a nichrome wire stirrer. When no nickel ion is added and a glass stirrer is employed, the diazonium xanthate precipitates and requires heat (32°) to effect decomposition. 

If the assumption of this reaction sequence is correct, the photolysis of tetraphenylphosphonium chloride must then only lead to biphenyl, diphenylphosphine, ethyl diphenyl-phosphinate and triphenylphosphine and its oxidation products. After 2 h of irradiation, biphenyl, diphenylphosphine and its oxidation products, triphenylphosphine and triphenylphosphine oxide, in a ratio of 3 1 5, along with raw material, are obtained. Ethyl diphenylphosphinate was detected in trace amounts7. These results support the postulate of the reversibility of phosphoranyl radical formation in such systems and indicate one-electron transfer processes15 in the formation and decomposition of the tetraarylphosphonium cation. This reaction is comparable to the observation of an electron transfer from halide ions to hydroxyl radicals or hydrogen atoms in aqueous solutions16,... 

The dependence of the rate upon the inverse of the hydrogen ion concentration (base-catalysis) is reasonably attributed to the necessity for the coordinated water molecule to lose a proton. The resulting ethyl-ene-hydroxypalladium species (the cis isomer), I, is then believed to undergo an internal addition reaction of the hydroxyl group to the coordinated ethylene to form the dichloro-2-hydroxyethylpalladium anion, II. The final step is a decomposition of the last compound into acetaldehyde, palladium metal, hydrogen ion and chloride anions. 

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