Dipropyl sulphide

Formation of a symmetrical sulphide (a) (e.g. dipropyl sulphide, Expt 5.204), is conveniently effected by boiling an alkyl halide (the source of carbocations) with sodium sulphide in ethanolic solution. Mixed sulphides (b) are prepared by alkylation of a thiolate salt (a mercaptide) with an alkyl halide (cf. Williamson s ether synthesis, Section 5.6.2, p. 583). In the case of an alkyl aryl sulphide (R-S Ar) where the aromatic ring contains activating nitro groups (see Section 6.5.3, p. 900), the aryl halide is used with the alkyl thiolate salt. The alternative alkylation of a substituted thiophenol is described in Section 8.3.4, p. 1160. The former procedure is illustrated by the preparation of isobutyl 2,4-dinitrophenyl sulphide (Expt 5.205) from l-chloro-2,4-dinitrobenzene and 2-methylpropane-1-thiol. 

Place 56 g (0.5 mol) of finely powdered, fused sodium sulphide and 100 ml of rectified spirit in a 500-ml round-bottomed flask equipped with a reflux condenser. To the boiling mixture add 46 g (34 ml, 0.374 mol) of propyl bromide slowly and reflux for 6 hours. Distil off the ethanol on a water bath, and add a large excess of water to the distillate. Separate the upper layer of crude sulphide, wash it with three 40-ml portions of 5 per cent sodium hydroxide solution, then with water until the washings are neutral, and dry over anhydrous calcium chloride or anhydrous calcium sulphate. Distil, and collect the dipropyl sulphide at 141-143 °C. The yield is 20g (91%). If the sulphide is required perfectly pure, it should be redistilled from a little sodium. 

Dipropyl sulphide Dipropyl disulphide Dipropyl trisulphide... 

Dimethyl sulphide-dg (d6-DMS), dipropyl disulphide (DPDS), 3-(methylthio)-l-hexanol (MTH) and 4-methylthiazole (MT) have been used as internal standards for different compounds or groups of them. 

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