V — 155 



on treating methylheptenol with dilute sulphuric acid, and, probably, an un 

 saturated hydrocarbon. Attempts at reducing citronellal remained without 

 result. With citral, Law was more successful. This aldehyde afforded a mix- 

 ture of geraniol with an unstable isomeric alcohol, b.p. about 220°, as well 

 as a non-volatile compound C20H34O2, which is perhaps identical with the 

 pinacone-like compound prepared by Verley 1 ). Menthone yielded a mixture 

 of menthol and two isomeric menthopinacones. As a reduction-product 

 of d-carvone (^oH^l^S'), Law obtained a body with b. p. between 260 

 and 262° (40 mm.), as well as «-carvelone (m. p. of the oxime 228°) and 

 an as yet unknown isomeric carvelone, of which the oxime melted at 228°. 

 Reduction of pulegone in alkaline solution gave rise to menthone, pulego- 

 pinacone (m. p. 119°), and menthopinacone (m. p. 148°); using sulphuric 

 acid as a cathode liquid the result was menthol, menthone, and pulego- 

 and menthopinacone. Cinnamic aldehyde resinified both in acid and in 

 alkaline solution; in a solution of potassium acetate it yielded /^-phenyl-' 

 propylalcohol. 



P. Sabatier and A. Mailhe 2 ) describe an interesting method of preparing 

 aldehydes. Over titanium oxide heated to 250 to 300° they pass the vapours 

 of a fatty acid mixed with an excess of formic acid vapour. From the fatty 

 acid the corresponding aldehyde is produced, carbon-monoxide and -dioxide 

 being liberated. Acetic acid yielded 50 p. c, propionic acid 40 p. c, butyric 

 acid 55 p. c, isobutyric acid 65 p. c, isovaleric acid 75 p. c, isobutylacetic 

 acid 80 p. c, caprylic acid 90 p. c. and pelargonic acid 85 p. c. of the corre- 

 sponding aldehyde. It is not easy, by this method, to convert benzoic acid 

 into benzaldehyde; phenylacetic acid yields 75 p. c. phenylacetaldehyde. 



Ketones. 



On the electrolytical reduction of ketones see above. 

 On the production of «-ionane from ionone, see p. 166. 



O.Wallach 3 ) has found that the two ketones q/dopentene-pentanone and 

 dic^/dopentene-pentanone are capable of easy reduction by PaaFs method, 

 |into the saturated ketones Ci Hi 8 O and Ci5H 26 0. In the course of this con- 

 version ci/c/opentene-pentanone forms cydopentyl q/cfopentanone (b.p. 232 to 

 233°; d 2 io 0,9745) a body with a pronounced odour of menthone. In an an- 

 alogous manner as has been proved to be the case with q/cfohexylhexanone 4 ), 

 q/cZopentylpentanone splits up during oxidation with chromic acid into a 



!) Bull Soc. chim. III. 21 (1899), 409. 

 2 ) Compt. rend. 154 (1912), 561. 

 ») Liebiga Annalen 389 (1912), 178. 

 4 ) Comp. Report October 1911, 146. 



