Preparation of sulfides and sulfonium salts

Sulfides (thioethers) can be obtained by replacing the halogen of alkyl and suitable aryl halides in a reaction with sodium sulfide, this being analogous to the preparation of thiols and disulfides. The reaction is usually carried out 

Preparation of the lower dialkyl sulfides by the following general procedure has been described by McAllan and his co-workers 286 Sodium sulfide nonahydrate (1.5 moles) is dissolved in water (250 ml) in a three-necked flask fitted with a reflux condenser, dropping funnel, and stirrer, then the alkyl halide (2 moles) is added slowly with vigorous stirring. When the very exothermic reaction ceases, the mixture is heated under reflux for a further 3 h and the sulfide is distilled over in steam, separated, washed with water, 10% sodium hydroxide solution, and again water, dried over calcium chloride, and distilled. In this way were obtained dimethyl (b.p. 37.3°), diethyl (b.p. 92°),287 diisopropyl (b.p. 119.8°), dipropyl (b.p. 142.8°),288 and bis-(2-cyanovinyl) sulfide (m.p. 142-143°, from ethyl acetate-cyclohexane).289 

Arylalkyl and aryl halides containing sufficiently reactive halogen also yield sulfides by this method. 

Bis-(2-naphthylmethyl) sulfide 290 Sodium sulfide nonahydrate (25), dissolved in water (15 ml) and anhydrous ethanol (230 ml), is added to 2-(chloromethyl)naphthalene (36 g), and the whole is heated under reflux for 6 h, allowed to cool, and poured into water. The precipitate is collected and recrystallized from alcohol, giving the sulfide (84.4%, 26.5 g), m.p. 123-124°. 

Bis-(4-chlorobenzyl) sulfide is obtained in 85.7 % yield analogously from 4-chlorobenzyl chloride.290 

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