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Ethyl P-chlbrovinyl ether can be obtained easily from chloroacetaldehyde diethylacetal .by heating with .potassium pyrosulphate. The product .contains a large proportion of the cis-isomer. T,he required acetal has been .prepared from paraldehyde. alcohol and chlorine.The method ,has been a,pplied also ,for the synthesis of butyl p-chlorovinyl ether.Ethyl 1-chlorovinyl ether can also be prepared continuously by passing chloroacetal vapour a t 220-230" over pumice impregnated with 4 % of potassium bisulphate.T h e conversion of trans-into cis ethyl /?-chlorovinyI ether by irradiation in the presence of .traces of bromine is described.A convenient way for obtaining ethoxyethyne, 11, in ,the laboratory is ,by heating cis ethyl /?-chlorovinyl ether, I, with powdered potassium hydroxide 1 -4 ) .

Photoemissive thresholds were determined of a number of donor–acceptor complexes (tetramethyl-p-phenylenediamine and p-phenylenediamine as donors with chloranil and bromanil as acceptors) by extrapolation of the wavelength-vs-photocurrent curves to zero current. These thresholds were compared with those of the constituent components. The thresholds of the complexes are found to be somewhat higher than those of the donors (by about 0.1–0.2 eV) and also the behavior of the wavelength-vs-photocurrent curves near the threshold appears to be different. The observed phenomena are consistent with a model in which the lattice of a donor–acceptor complex contains neutral molecules as well as ions.

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