— 188 — 



This constituted a liquid of a menthone-like odour, boiling at 58 

 to 6o° (10 mm.), giving aldehyde-reactions with silver-salts and fuch- 

 sine- solution, and yielding a solid semicarbazone of which the m. p. 

 is not stated. 



A series of other bodies was also obtained by reduction, but these 

 lie outside our special branch and are therefore of no interest to us. 



On the determination of citral, see Analytical Notes, p. 152. 



Pinonic aldehyde. Some time ago, Harries 1 ) expressed the 

 surmise that when pinene ozonide is decomposed by heating it with 

 water, there is formed, in addition to pinonic acid, an aldehyde which 

 is probably pinonic aldehyde. A fresh investigation conducted by 

 C. Harries and H. von Splawa-Neyman 2 ) has established the fact 

 that the decomposition of the hydroaromatic ozonides can be more 

 easily carried out by warming with glacial acetic acid than with water, 

 and that, if this is done in the case mentioned above, the formation 

 of the assumed pinonic aldehyde is facilitated. Pinene ozonide was 

 heated with acetic acid on the water-bath to 90 , and the residue 

 (after evaporating the acetic acid in vacuo) was fractionated. A fraction 

 boiling between 100 and 142 (12 mm.), which strongly reduced 

 ammoniacal solution of silver and Fehling's solution, formed a semi- 

 carbazone, m. p. 214 to 2 1 5 . Analysis showed this to be a di-semi- 

 carbazone, probably that of pinonic aldehyde, C 10 H 16 O 2 . 



Piperonal. Pauly and Alexander 3 ) have again investigated the body 

 known as dichloro -piperonal, which according to the latest researches is to 

 be definitely regarded as a carbonate of 3,4-dihydroxybenzakhloride. An 

 attempt was made to saponify the body into the corresponding pyro- 

 catechol, but in this process protocatechuic aldehyde was always formed. 

 Only by saponification with the theoretically required quantity of water in 

 the presence of dry pyridin no aldehyde was obtained, but in lieu 

 thereof there was formed a coloured chlorinated body which could not 

 be obtained in the pure state and which gave the impression of being 

 a pyridinium compound. The readiness with which the two chlorine 

 atoms react is ascribed by the authors as connected with the mobility 

 of chlorine atoms in the presence of a phenolic hydroxyl group in 

 para position which has been observed by various investigators, inasmuch 

 as aldehyde formation also occurred when only the para-hydroxyl 

 of dichloropiperonal was liberated, as in the saponification with pyridin 

 (or sodium acetate) in a methyl-alcoholic solution, in which the mono- 



.(i)CHO 

 methyl carbonate of protocatechuic aldehyde, C 6 H 8 H3)O.CO.OCH 3 , 

 \( 4 }OH 



*) Berl. Berichte 41 (1908), 38; Report April 1908, 178. 

 2 ) Berl. Berichte 42 (1909), 879. 

 ■) Berl. Berichte 42 (1909), 2350. 



