472 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



possible, depending upon whether the acetals are combined with the a,^- 

 carbons of glycerol or with the a,Q!'-carbons. The two types of plasmalo- 

 gens are illustrated in the structural formulas of Q!,Q:'-stearylidene and of 

 Q!,;S-stearylidene. 



KNCHjCHgO-PO-CH CH(CHj),sCH3 



a, a '-Stearyli dene 



HgCOy 



I )CH(CHj),6CHs 



hcq/ 



I II 

 H^COP-OCHjCHjNHj 



OH 



a,/3-Stearylidene 



The assumption that an acetal linkage exists in the case of the aldehyde 

 (acetal) group is substantiated by the difficulty encountered in the hy- 

 drolysis of the nitrogen-free group with alkali, and by its sensitivity to acids 

 and also to mercuric chloride. 



(S) Properties of the Plasmalogens 



The plasmalogens which have thus far been prepared have no definite 

 melting points, although they become soft at 50°C. and decompose above 

 150°C. They dissolve in aqueous potassium hydroxide, but are insoluble 

 in water. They are soluble in hot ethyl alcohol, and also to a greater ex- 

 tent in methyl alcohol; they are sparingly soluble in cold ethanol. Chloro- 

 form is an excellent solvent. However, they dissolve only slightly in other 

 lipid solvents such as acetone, petroleum ether, and diethyl ether. When 

 separated from an alcoholic solution by rapid cooling, the acetals form an 

 amorphous waxy mass; on slow cooling, on the other hand, globular aggre- 

 gates result, which appear as long crystals. 



Several methods for the estimation of plasmalogens have been sug- 

 gested, all of which are based upon the Schiff reagent for the detection of 

 aldehydes. 27'='s'^'='86 



(3) Hydrolysis of the Plasmalogens 



Plasmalogens can be split into colamine glycerophosphate and a higher 

 aldehyde on treatment with mercuric chloride. When saponified with 

 3.3% sodium hydroxide for 6 hours, plasmalogen forms colamine and plas- 

 malogenic acid. The latter product can be separated as the lithium salt; 



385 R. Feulgen and H. Griinberg, Z. physiol. Chem., 257, lGl-172 (1939). 

 »86 H. Waelsch, J. Biol. Chem., UO, cxxxvi (1940). 



