— 155 — 



is superior to ionone, especially as regards its great stability and 

 richness, and also the simplicity of its production. The cyclo- 

 citrylidene propenal recently obtained by Barbier 1 ), which when 

 freshly produced develops a very pleasant flower -like odour strongly 

 reminding of violets, but which has not the cedarwood-like secondary 

 odour peculiar to ionone, also suffers from the fault that it loses 

 already in a short time the freshness and charm of its scent, owing 

 to ready oxidation. By condensing equimolecular quantities of citral 

 and propylic aldehyde in aqueous-alcoholic solution by means of 

 dilute soda liquor, Barbier obtained an unsaturated aldehyde of the 

 formula C 13 H 20 O. The condensation -product appears to consist of 

 t wo isomeric aldehydes, which boil at 147 to 148 and 158 to 160 

 / 1 6 mm. pressure) respectively. Its constitutional formula is as follows : — 

 (CH 3 ) 2 : C : CH ■ CH 2 ■ CH 2 . CH 2 • C(CH 3 ) : CH . CH : C(CH 3 ) - CHO 



When treated with 60 per cent, sulphuric acid, at first at a low 

 temperature, subsequently at 50 to 6o°, the readily oxidisable aldehyde 

 yields the isomeric cyclic aldehyde of the formula 



CH, 



CH 2 



CH, 



C 



CCH:C(CH 3 )CHO 



,C:(CH 3 ) 2 



CH 



which like its isomeride ionone, may possibly consist of two isomerides, 

 boiling at 123 to 125 and 132 to 133 . The semicarbazone of the 

 one distillate melts at 174 to 1 75 ; that of the other has hitherto 

 only been obtained in an oily form. 



Citronellal. In continuation of the work done by R u p e and L o t z 2 ), 

 H. Rupe, S. Pfeiffer, and J. Splittgerber 3 ) communicate the results 

 of their studies of condensations with citronellal. According to this, 

 the citronellidene acetic acid of the b. p. 175,5 to 1 77>5° ( x 4 mm - 

 pressure) first described by the first -named authors, whose melting 

 point was found by Knoevenagel and Griinhagen at 51 to 52 , 

 consists of a mixture of two isomerides. Further experiments namely, 

 have shown that when the assumedly uniform acid of the above-named 

 boiling point is treated with sulphuric acid, a lactone is formed. But 

 from this it is clear that on condensing citronellal with malonic acid, 



*) Compt. rend. 144 (1907), 1442. 



2 ) Berl. Berichte 36 (1903), 2796; Report April 1904, III. 



3 ) Ibidem 40 (1907), 18 13. 



