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Aldehydes. 
Citral. Condensation of cyclic ketones with zinc and iodaceti(^ 
ester, and subsequent hydrolysis, produces oxy esters of the formula 
CHg • CO2 C2 Hr^ 
which are converted into unsaturated esters by splitting off water. 
When applying this reaction to citral, Tetry^) obtained, besides a 
lactone Cj^ 4 O3 of the boiling point 160° at 10 mm, citralidene 
acetic ester as a pleasantly smelling oil of the boiling point 129° at 
9 mm. On saponifying the ester with alcoholic potash solution, citral- 
idene acetic acid was obtained as a colourless mobile oil of the boiling 
point 175°, at 18 mm. 
Ketones. 
According to observations made by Wallach^j, alkylated cyclo- 
hexenones which contain a double linkage in the ring, can, like the 
saturated cyclic ketones of various ring-systems, be condensed with 
brominated fatty esters by means of zinc. He examined more particularly 
methyl and dimethyl cyclohexenones, and also methyl ethyl and iso- 
propyl cyclohexenones. But the oxy esters R^' : C (O H) C Hg • C O2 R 
which occur first of all when using saturated ketones, cannot be iso- 
lated when unsaturated ketones are employed; — on the contrary, the 
compounds which contain one molecule water less, are those always 
met with. Probably, the double linkage formed by the elimination of 
water, immediately transfers itself to the nucleus, so that the acids 
formed on saponification must be considered as dihydroaromatic acids. 
Under suitable conditions the latter lose carbon dioxide with formation 
of hydrogenated benzene hydrocarbons, which can be converted into 
benzene derivatives; and the facility with which hydrogen is split off 
appears to increase with the growing molecular weight, and also to be 
rendered more easy by the entry of certain atom-groups, such as, for 
example, isopropyl. 
In conformity wdth these experiences is the behaviour of carvone, 
already communicated on a previous occasion; just as little as from 
this body, can an oxyester be obtained from carvenone, whose ethylene- 
linkage is situated in the nucleus. On the other hand, dihydro- 
carvone with a saturated ring is capable of forming a stable oxyester. 
1) Bull. Soc. chim. III. 27 (1902), 601. 
^) Liebigs Annalen 323 (1902), 135. 
