260 



SULPHUR COMPOUNDS 



[170-D. 



170. Pheiiylethyl Isothiocyauate, 

 Thiocarbimide, or Mustard Oil. 



C 6 H 5 .CH 2 .CH 2 .NCS 



NATURAL SOURCES. 



Occurs in the ethereal oil of the 

 water- cress, Nasturtium ojficinale, and 

 the winter-cress, Barbarea prcecox. The 

 glucoside (gluconasturtiin) exists as 

 potassium salt in the seeds of these 

 plants (Gadamer, Ber. 32, 2339 ; Arch. 

 Pharm. 237, 507). According- to Ber- 

 tram and Walbaum (Journ. pr. Ch. [2] 

 50, 557), this mustard oil is contained 

 in the ethereal oil from the roots of 

 Reseda, 



SYNTHETICAL PROCESSES. 



[A.] From toluene [54; A, &c.] and 

 potassium cyanide [172] through benzyl 

 cyanide (see under benzyl mustard oil 

 [169 ; H]) and carbon disulphide [160]. 

 Benzyl cyanide on reduction gives w- 

 phenylethylamine (Spica and Colombo, 

 Gazz. 5, 124; Bernthsen, Ann. 184,304; 

 Spica, Jahresber. 1879, 440 ; Laden- 

 burg, Ber. 19, 783). The amine gives 

 the mustard oil by the general method 

 (Neuberfc, Ber. 19, 1825). 



The nitrile of symmetrical triphenyl- 

 glutaric acid, obtained by the condensa- 

 tion of benzyl cyanide with benzoic 

 aldehyde [114] by means of sodium 

 ethylate (Meyer, Ann. 250, 156), gives 

 6o-phenylethylamine on reduction with 

 sodium in alcoholic solution (Henze, 

 Ber. 31, 3065). 



Or benzyl chloride can be combined 

 with the sodium compound of chlor- 

 tnalonic ester [Vol. II] (Conrad and 

 Bischoff, Ann. 209, 219) so as to give 

 benzyl chlormalonate (Conrad, loc. cit. 

 243). The latter, on treatment with 

 potassium or barium hydroxide, gives 

 benzyl tar tronic acid (Ibid. 245), and 

 this yields phenyl-u-lactic acid on heat- 

 ing at 1 60-1 80 (Ibid. 247). Subsequent 

 steps as balow under D. 



A\so ivom benzene [6; I,&c.] through 

 ethylbenzene (see under phlorol [64 ; 

 A]). The compound of the latter with 

 chromium oxychloride is decomposed 



by water with the formation of a-toluic 

 aldehyde (Etard, Ann. Chim. [5] 22, 

 248), the oxime of which (Dollfus, 

 Ber. 25, 1917) gives phenylethylamine 

 on reduction (Bischler and Napieralski, 

 Ber. 26, 1905). Ethylbenzene also 

 yields a-toluic aldehyde among the pro- 

 ducts of its oxidation by potassium 

 persulphate (Moritz and Wolffenstein, 

 Ber. 32, 434). 



Or from ethylbenzene through styr- 

 ene bromide (see under styrene [7 ; A]), 

 and then as below under B. 



[B.] Styrene [7] gives ethylbenzene 

 (see under phlorol f 64; B]), which, with 

 carbon disulphide [160], yields the mus- 

 tard oil as above under A. 



Or styrene can be combined with 

 bromine, and the bromide converted 

 into the glycol (see under benzoic alde- 

 hyde [114; B]). The latter on heating 

 with 20 per cent, sulphuric acid gives 

 a-toluic aldehyde (Zincke, Ber. 11, 1402; 

 Ann. 216, 301 ; also Tiffeneau, Comp. 

 Rend. 134, 1505), which can be con- 

 verted into phenylethylamine as above 

 under A. 



Or styrene, by the action of iodine in 

 presence of mercuric oxide, gives an 

 iodo-derivative, which yields a-toluic 

 aldehyde on treatment with silver nitrate 

 (Bougault, Comp. Rend. 131, 529). 



[C.] From tartaric or racemic acid 

 [Vol. II], and n-propyl alcohol [15], 

 and carbon disulphide [160], through 

 pyroracemic acid and propionic alde- 

 hyde, ethylisophthalic acid, ethylben- 

 zene, &c. (see under phlorol [64; J]). 



NOTE : Generators of pyroracemic acid are 

 given under benzyl alcohol [54 ; F ; I ; M, &c.]. 



[D.] From benzoic aldehyde [114], 

 alcohol [14], acetic acid [Vol. II], and 

 carbon disulphide [16O]. Chloracetic 

 ester and benzoic aldehyde on treatment 

 with sodium in alcoholic solution give 

 the ester of /3-phenyloxyacrylic == 

 phenylglycidic acid (Erlenmeyer, Ann. 

 271, 153). The latter yields a-toluic 

 aldehyde on distillation with dilute 

 sulphuric acid (Baeyer, Ber. 13, 304 : 

 see also Glaser, Ann. 147, 100). Phenyl- 

 glycidic acid decomposes at ordinary 

 temperatures into a-toluic aldehyde and 

 carbon dioxide (Erlenmeyer, Ber. 13, 

 308). 



