190 



ALDEHYDES AND KETONES : FATTY GROUP [100-103. 



to the extent of 8-5 per cent. (Stephan, 

 Journ. pr. Ch. [2] 62, 523). 



The aldehyde has been found also in 

 oil of mandarin orange (Schimmel's 

 Ber. Oct. 1901 ; Ch. Centr. 1901, 2, 

 1007), and it may possibly occur in oil 

 of lemon (Ibid. Oct. 1902 ; Ch. Centr. 

 1902, 2, 1207). 



SYNTHETICAL PROCESS. 



[A.] From n-decoic and formic acids 

 [Vol. II] by distilling a mixture of the 

 barium salts (Krafft, Ber. 16, 1717; 

 Schimmel & Co., Germ. Pat. 126736 

 of 1900; Ch. Centr. 1901, 2, 1375). 



101. Acrolein ; Acrylic Aldehyde ; 

 Fropenal. 



CH 2 :CH.CHO 



NATURAL SOURCE. 



Occurs in rancid fat ; probably a 

 bacterial product (Nagel, Am. Ch. 

 Journ. 23, 172). 



SYNTHETICAL PROCESSES. 



[A.] From gtycerol [48] by heating 

 with dehydrating agents (see under 

 mannitol [51; B]). 



[B.] From acetone [106] through 

 the dibromide ([Ibid. C] ; also glycerol 

 [48; E]). 



[C.] From alcohol [14] and acetic 

 acid [Vol. II] through diiodacetone 

 (glycerol [48 ; K]). 



[D.] From mannitol [5l] (glycerol 

 [48; O]). 



[E.] From dextrose [154], being 

 among the products of oxidation by 

 chromic acid or by sulphuric acid and 

 manganese dioxide (Liebig, Ann. 113, i). 



[F.] From normal or isopropyl alcohol 

 [15 ; 16] through the compound of 

 propylene with mercuric sulphate (ben- 

 zyl alcohol [54; E]). 



NOTE : For generators of propylene see under 

 glycerol [48 ; B to O] ; also under isopropyl 

 alcohol [16]. 



102. Crotonic Aldehyde ; 

 2-Butenal. 



CH 3 .CH:CH.CHO 



NATURAL SOURCE. 



Said to have been found in the first 

 runnings from spirit rectification 

 (Kramer and Pinner, Ber. 3, 76). Bio- 

 chemical origin doubtful. 



SYNTHETICAL PROCESSES. 



Syntheses of crotonic aldehyde are 

 given under n-butyl alcohol [l?]. 



[A.] From acetic aldehyde [92] (n- 

 butyl alcohol [17 ; G]). 



[B.] From en/thritol [50] W& formic 

 acid [Vol. II] (ibid. [17; I]). 



[C.] From malic acid [Vol. II] 

 through coumalic acid or by electro- 

 lysis (Ibid. [17 ; O]). 



[D.] From acetylene [l; A, &c.] 

 (Ibid. [17 ; I, note]). 



[E.] From formic and acetic esters 

 [Vol. II] (Ibitl [17 ; J]). 



[F.] From ethylene through vinyl 

 bromide (Ibid. [17; I, note]). 



[G.] From lactic acid [Vol. II] (Ibid. 

 [17 ; I, note]). 



[H.] From fi-fydroosybutyric acid 

 [Vol. II] (Ibid. [17 ; I, note]). 



[I.] From tetramethylenediamine [Vol. 

 II] through /3-butylene glycol [17; P]. 

 Crotonic aldehyde is among the pro- 

 ducts of oxidation of the glycol. 



103. Tiglic Aldehyde ; Guaial ; 

 2-Methyl-2-Butenal. 



CH 3 .CH:C(CH 3 ).CHO 



NATURAL SOURCE. 



The aldehyde does not occur in the 

 free state, but the complex exists in 

 some constituent of guaiacum resin 

 from the W. Indian Guaiacum officinale. 

 The resin gives tiglic aldehyde on dry 

 distillation (Volckel, Ann. 89, 346 ; 

 Herzig, Monats. 3, 118; 822; 825). 

 The acid of guaiacum resin, guaiaretic 

 acid, does not appear to be the source 



