— i53 — 



The reaction proceeds in two phases. There is first of all formed, 

 with abstraction of water, a lactide, which on further heating splits up 

 into CO and aldehyde. 



I. CH 3 (CH 2 ) 7 CH — COOH = CH 3 (CH 2 ) 7 CH — CO + H 2 G. 



OH O^ 



II. CH 3 (CH 2 ) 7 -CH-CO = CH 8 (CH 2 ) 7 — CHO + CO. 



Of the two aldehydes, various derivatives suitable for identification 

 were produced. The oxime of decylic aldehyde melts at 69 ; the 

 semicarbazone of nonylic aldehyde at ioo°. The latter statement 

 leads Harries and Turk 1 ) to a rectification of their previous com- 

 munications. They had found for the melting point of the semicarbazone 

 of nonylic aldehyde 84 2 ). But a subsequent check test showed that 

 this compound melts at ioo°, in agreement with Bagard's observ- 

 ation, if it is produced from the aldehyde purified by the bisulphite 

 compound. 



Protocatechuic aldehyde. Among the derivatives of pyro- 

 catechol, protocatechuic aldehyde, valuable for syntheses on account 

 of its aldehyde-group, and also employed for the production of vanillin, 

 possesses in a special degree properties which do not render it parti- 

 cularly inviting for working up. H. Pauly 8 ) endeavoured to convert 

 piperonal directly into the cyclic carbonate, thus avoiding protocatechuic 

 aldehyde, i. e., to change in the piperonal the group :0 2 CH 2 into 

 :0 2 CO. Finally he succeeded to replace in dichloropiperonal 4 ) 

 obtained from piperonal, the two chlorine atoms by oxygen and so 

 to produce the cyclic carbonic acid ester. Fit tig and Remsen 

 were unable, in the attempt made by them of decomposing the 

 dichloropiperonal, to isolate the carbonate, as it is spontaneously decom- 

 posed further by boiling water. This can only be successfully accom- 

 plished if water is allowed to act in masked form, or indirectly, on 

 the dichloride. For this purpose anhydrous oxalic acid for example is 

 very suitable; at about 130 it reacts with dichloropiperonal according 

 to the following equation : — 



C1 2 C0 2 : C 6 H 3 CHO -f (COOH), = OC0 2 : C 6 H 3 CHO + 2 HC1 -f CO, + CO. 



Concentrated sulphuric acid can also be employed in combination 

 with water for the conversion of the group : 2 C Cl 2 into : 2 C O ; 



*) Berl. Berichte 40 (1907), 2756. 



2 ) Ibidem 39 (1906), 3733. 



8 ) Ibidem 40 (1907), 3096; German Patent application P. 18466, Class 120. 



4 ) Liebig's Annalen 159 (1871), 126. 



