MUSTARD OILS, organic chemical compounds of general formula R-NCS. They may be prepared by the action of carbon bisulphide on primary amines in alcoholic or ethereal solution, the alkyl dithio-carbamic compounds formed being then precipitated with mercuric chloride, and the mercuric salts heated in aqueous solution, or the isocyanic esters may be heated with phosphorus pentasulphide (A. Michael and G. Palmer, Amer. Chem. Jour., 1884, 6, 257). They are colourless liquids with a very pungent irritating odour. They are readily oxidized, with production of the corresponding amine. Nascent hydrogen converts them into the amine, with simultaneous formation of thio-formaldehyde, RNCS+4H = R-NH 2 +HCSH. When heated with acids to 100 C, they decompose with formation of the amine and liberation of carbon bisulphide and sulphuretted hydrogen. They combine directly with alcohols, mercaptans, ammonia, amines and with aldehyde ammonia.
Methyl mustard oil, CH S NCS, melts at 35 C.and boils at nq C. Allyl mustard oil, CjHsNCS, is the principal constituent of the ordinary mustard oil obtained on distilling black mustard seeds. These seeds contain potassium myronate (CioHiaNSjOioK) which in presence of water is hydrolysed by the myrosin present in the seed, It may also be prepared by heating allyl sulphide with potassium sulphpcyanide. It is a colourless liquid boiling at 150-7 C. It combines directly with potassium bisulphite. Phenyl mustard oil, CeHsNCS, is obtained by boiling sulphocarbanilide with concentrated hydrochloric acid, some triohenylguanidine being formed at the same time. It is a colourless liquid boiling at 222 C. When heated with copper powder it yields benzonitrile.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)