222 



AROMATIC ALDEHYDES AND KETONES [121 1-122 A. 



[120 ; B]), which hydrolyse to vera- 

 troylcarbonic acid. The latter, on heat- 

 ing- with aqueous potash at 160-170, 

 gives, among- the products of its de- 

 methylation, vanilloylcarbonic acid, and 

 this yields vanillin as below under K. 



[J.] Isoeugenol [79] gives vanillin on 

 oxidation by ozone or on electrolysis of 

 a solution of one of its salts (F. v. 

 Heyden, Nachf. Germ. Pat. 92007 of 

 1895; Ch. Centr. 1897, 2, 454; Otto 

 and Verley, Germ. Pat. 97620 of 1895 ; 

 Ch. Centr. 1898, 2, 693; Verley, Am. 

 Pats. 553593 and 563039 of 1896). 

 Also by oxidation with metallic per- 

 oxides in alkaline solution (Haarmann 

 and Reimer, Germ. Pat. 93938 of 1896; 

 Ch. Centr. 1897, 2, 1166). Isoeugenol 

 gives vanillin by ' contact ' oxidation 

 on passing the vapour mixed with air 

 over heated platinum (Trillat, Comp. 

 Rend. 133, 822). 



/Isoeugenylsulphuric acid (potassium 

 salt) on oxidation with ozone gives po- 

 tassium vanillyl sulphate, and this yields 

 vanillin on decomposition by dilute 

 acids (Verley, Bull. Soc. [3] 25, 48). 

 Or isoeugenol can be benzylated by 

 means of benzyl chloride (see under 

 benzyl alcohol [54 ; A]), and the 

 benzyl ether oxidised to the methyl 

 benzyl ether of protocatechuic aldehyde, 

 which splits off benzyl and gives 

 vanillin on heating with hydrochloric 

 acid (Bohringer & Sohne, Germ. Pat. 

 65937 of 1891 ; Ber. 26, Ref. 211). 



Or isoeugenyl acetate, on oxidation 

 with potassium permanganate, gives 

 vanilloylcarbonic = p-hydroxy-m-meth- 

 oxybenzoylcarbonic acid, and this yields 

 vanillin on heating above its melting 

 point (Tiemann, Ber. 24, 2878), on 

 heating with aniline and decomposing 

 the anilide by heating with dilute sul- 

 phuric acid (Gassmann, Comp. Rend. 

 124, 38), or by heating with dimethyl- 

 aniline (Bouveault, Bull. Soc. [3] 19, 76). 



NOTE : For production of vanillin by the 

 oxidation of isoeugenyl acetate or benzoate see 

 also Haarmann and Reimer, Germ. Pat. 57568 

 of 1890 ; Ber. 25, Ref. 93 ; also Germ. Pat. 

 63027 of 1891 ; Ber. 25, Ref. 824. 



Isoeugenol can be combined with 

 phenylhalogenacetic acids or their 



amides, nitriles, or ethers, or with o>- 

 halogen-toluic acids so as to form the 

 corresponding isoeugenol-ether acids. 

 These are oxidised by acid and a di- 

 chromate with the formation of the cor- 

 r&ponding vanillin-ether acids, and the 

 latter give vanillin (and the ether-acid) 

 on decomposition by mineral acid 

 (Majert, Germ. Pat. 82924 of 1894; 

 Ber. 28, Ref. 878). 



[K.] From toluene [54] through m- 

 chlor-p-nitrotoluene, the corresponding 

 chlornitrobenzyl chloride or bromide, and 

 the corresponding aldehyde by oxidation 

 with lead or copper nitrate. The chlor- 

 nitrobenzoic aldehyde on heating with 

 sodium methoxide exchanges chlorine 

 for the methoxy-group, and the p-nitro- 

 m-methoxybenzoic aldehyde can be con- 

 verted into vanillin as above under C 

 (Landsberg, Germ. Pat. 37075 of 1886 ; 

 Ber. 19, Ref. 861). 



Or from toluene through ortho- or 

 paratoluidine, m-(3)-nitro-p-toluidine, 

 and m-nitrotoluene (Beilstein and Kuhl- 

 berg, Ann. 158, 346). The latter gives 

 m-nitrobenzoic aldehyde by electrolytic 

 oxidation (Pierron, Bull. Soc. [3] 25, 

 852). Subsequent steps as above 

 under C. 



122. Piper onal ; Protocatechuic 



Aldehyde Metliylene Ether ; 



Heliotropin. 



CHO 



NATURAL SOURCES. 



Said to occur in oil of Spiraa (Schnee- 

 gans and Gerock, as quoted by Gilde- 

 meister and Hoffmann, p. 551). Ac- 

 companies vanillin from certain species 

 of Vanilla (Busse, Ch. Centr. 1900, 1, 

 558). 



SYNTHETICAL PROCESSES. 



[A.] From cafecJiol [69] 

 protocatechuic aldehyde by the action of 



through 



