Sensitized photooxidation of a model 1,4‐diene, 4cis, 7cis‐undecadiene, was shown to yield 4‐hydroperoxy‐5trans,7cis‐undecadiene and 5‐hydroperoxy‐3trans,7cis‐undecadiene as initial products. Further irradiation (in the presence of the sensitizer) caused the isomerization of 4‐hydroperoxy‐5trans,7cis‐undecadiene to 4‐hydroperoxy‐5trans,7trans‐undecadiene. Oxidation of 4cis,7cis‐undecadiene with chemically formed singlet oxygen gave the same initial products as the photosensitized oxidation. 5‐Hydroperoxy‐3trans,7cis‐undecadiene is, however, not formed in the radical autoxidation of the diene. It is concluded that singlet oxygen is the reactive intermediate in the photooxidation. Comparison with this model reaction suggests that the photooxidation of refined soybean oil in propanol also proceeds via singlet oxygen: the photooxidations of both 4,7‐undecadiene and soybean oil are inhibited by β‐carotene and by triethylamine, but unlike radical chain autoxidation, they are not inhibited by 2,6‐di‐t‐butyl‐4‐methylphenol. Also soybean oil can act as a sensitizer for the photooxidation of 4,7‐undecadiene. Chlorophyl‐like sensitizers are probably unimportant in the well refined soybean oil used in this work. The observed photooxidation of the skipped dienoic components of soybean oil, which is probably due to some other, unidentified sensitizer(s), absorbing below 500 nm, can be avoided by using a yellow filter.

In a previous paper we reported that photoexcited SO2 reacts with alcohols, ethers, sulfides and chlorides to form a-substituted alkanesulfinic acids'. Here we report the formation of carbenium ions by reaction of photoexcited SOz with trialkyl orthoformates or benzaldehyde dimethyl acetal :When a 2.0 molar solution of e.g. trimethyl orthoformate in liquid SO, had been irradiated with UV-light' at -75°C for 18 h, ca. 40% of the orthoformate had reacted of which 65% was found back as the trimethoxymethyl cation** as appears from the following evidence.

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Acetylenic compounds RC = CH can be converted into acetylenic thioethers by treatment of the sodium or lithium alkynide with diethyl disulphide in liquid ammonia. This constitutes the easiest route to 1-ethylthio-I-alkynes I.Other compounds with "acidic" CH3, CH2 or CH groups can likewise be alkylthiolated; generally the product containing two geminal ethylthio groups is formed in excess.Disulphides RS-SR can be subjected to nucleophilic substitution ; carbanions, for instance, react with these compounds t o give a thioether and thiolate ion.In the literature a few examples of such conversions are recorded. The carbanions used were those in NaCH(S02R)Z 1, NaC(C&)3 z, RMgBr 3,495, RLi 2 , 6 . During these reactions a heterolytic cleavage of the -S-Sbond occurs, producing one RS@ and one RS@ particle, the first of which becomes attached to the carbanion.