06 III G-L.] 



HEXOIC ALDEHYDE 



187 



[G-.] From malonic andpropionic acids 

 [Vol. II] through propanetricarboxylic 

 ester, citraconic or mesaconic acid (see 

 under benzyl alcohol [54; M, note]), 

 and then as before. 



Or from malonic and acetic acid 

 through propanetricarboxylic ester by 

 the interaction of sodio-methylmalonic 

 ester and chloracetic ester, and pyro- 

 tartaric acid by hydrolysis of the tri- 

 carboxylic ester (Bischoff and v. Kuhl- 

 berg, Ber. 23, 635). Subsequent steps 

 as under I below and C above. 



Or malonic acid can be converted 

 into ethylmalonic (a-isopyrotartaric) 

 ester by the action of ethyl iodide on 

 sodio-malonic ester (Conrad, Ann. 2O4, 

 134 : see also Daimler, Ann. 249, 174), 

 chlorethylmalonic ester by chlorination 

 (Conrad, Ber. 14, 618 ; Conrad and 

 Guthzeit, Ann. 209, 232), or iodethyl- 

 malonic ester by the action of iodine 

 on sodio-ethylmalonic ester. The 

 chloro- or iodo-esters on hydrolysis 

 with baryta water give a-ethyltartronic 

 acid (Conrad and Guthzeit, loc. cit. 233 ; 

 Bischoff and Hausdorfer, Ann. 239, 

 127), and the latter on heating to 180 

 yields a-hydroxybutyric acid (Guthzeit, 

 Ann. 209, 234 ; Conrad, Ber. 14, 618), 

 from which propanal can be obtained 

 as under N, and the latter treated as 

 under A. Chlorethylmalonic ester also 

 gives a-hydroxybutyric acid on heating 

 with hydrochloric acid. 



[H.] From acetic and propionic acids 

 [Vol. II], alcohol [14], and potassium 

 cyanide [172] through a-methyl-^8- 

 cyanosuccinic ester and citraconic acid 

 (see under benzyl alcohol [54; M, note]). 

 Or from acetic acid through acetyl cyan- 

 ide, pyroracemic acid, and pyrotartaric 

 acid (see under benzyl alcohol [54; I]). 



[I.] From tartaric acid [Vol. II] 

 through pyrotartaric acid (see under 

 n-propyl alcohol [15 ; V]), citradi- 

 brom pyrotartaric acid by the action of 

 bromine and phosphorus on the latter 

 Auwers and Imhauser, Ber. 24, 2237), 

 and then as above under C. 



[J.] From propionic and oxalic acids 

 [Vol. II] and alcohol [14] through 

 methyloxalacetic ester, /3-methylmalic 

 acid, and citraconic or mesaconic acid 

 (see under benzyl alcohol [54 ; M]). 



Or from propionic acid through the 

 aa-dibromo-acid, the a/3-acid, glyceric 

 acid, and pyrotartaric acid ; or through 

 the aa-dibromo-acid, pyroracemic and 

 pyrotartaric acids ; or through propion- 

 amide, propionitrile, aa-dichlorpropionic 

 acid, pyroracemic and pyrotartaric acids 

 (see under benzyl alcohol [54 ; O]). 



Or from propionic acid through 

 .propionyl chloride and cyanide (Claisen 

 and Moritz, Trans. Ch. Soc. 37, 692). 

 The latter on hydrolysis gives ethyl- 

 glyoxylic acid = propionylformic or 2- 

 butanonic acid (Ibid, and Ber. 13, 

 2121), which is reduced by sodium 

 amalgam to a-hydroxybutyric acid, 

 from which propanal can be obtained 

 as under H", and 2-methylpentanal as 

 under A. 



Propanal is obtainable directly from 

 propionic acid by distilling the calcium 

 salt with calcium formate [Vol. II] 

 (Rossi, Comp. Rend. 7O, 129). 



[K.] From allyl isothiocyanate [166] 

 through allyl cyanide and pyrotartaric 

 acid (see under benzyl alcohol [54; F 

 and J]), and then as above under I 

 and C. 



[L.] From etftyl alcohol [14] through 

 iodof orm, acrylic acid, a-chlorlactic acid, 

 glyceric acid (see under benzyl alcohol 

 [54; I]), and then through pyrotar- 

 taric acid as above under B. 



Or from ethyl alcohol through ethyl 

 ether, dichlorether, chloracetaldehyde, 

 /3-chlorlactic acid, glyceric acid, and 

 pyrotartaric acid [54 ; I]. 



Or from ethyl alcohol through chlor- 

 acetal, chloracetaldehyde, /3-chlorlactic, 

 glyceric, and pyrotartaric acids [54; I]. 



Or through chloral, the cyanhydrin, 

 trichlorlactic acid, dichloracetaldehyde, 

 dichlorlactic acid, chloracetaldehyde, 

 /3-chlorlactic acid, &c. [54 ; I]. Or from 

 ethyl alcohol through ethylene, vinyl 

 chloride, chloracetaldehyde, ^3-chlor- 

 lactic acid, &c., as before (see under 

 benzyl alcohol [54 ; A]). 



NOTE : By this last method generators of 

 ethylene thus become generators of 2-methyl- 

 pentanal. 



Ethyl alcohol might be converted 

 more directly into propanal through 

 ethyl cyanide and propionic acid, and 



