200 ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



things, arose primarily in the waters of the surface of the 

 Earth long before the appearance of life on it. 



Like glycolic aldehyde, acetaldehyde can also undergo 

 condensation and we have already shown that acetaldehyde 

 must have been produced in the primaeval atmosphere by 

 the interaction of methane and carbon monoxide. When this 

 condensation occurs, aldol is formed, which can easily iso- 

 merise to give butyric acid. 



2 CH3.CHO->CH3.CHOH.CH2.CHO-> CH3.CH2.CH2.COOH 



Further condensation of aldol into more complicated pro- 

 ducts was found by S. M. Losanitsch and M. Z. Jowitschitsch 

 in an oily liquid which they obtained from acetaldehyde: 



n CH3.CHOH.CH2.CHO^ (CH3.CHOH.CH2.CHO)„ 



and further isomerisation of these products revealed one of 

 the possible methods of formation of the higher fatty acids. 

 Under somewhat difiFerent conditions crotonic condensa- 

 tion of acetaldehyde takes place : 



CH3.CHO-}-CH3.CHO->CH3.CH : CH.CHO -j- H2O 



The crotonaldehyde in its turn can condense with one 

 molecule of acetaldehyde giving rise to sorbic aldehyde: 



CH3.CH : CH.CHO-}-CH3CHO->CH3.CH : CH.CH : CH.CHO-I-H2O 



This can condense further : 



CH3.CH : CH.CH : CH.CHO + CHa.CHO^ 



CH3.CH : CH.CH : CH.CH : ch.cho + HsO, etc."" 



This is a method of synthesising polyenes, compounds with 

 conjugated double bonds ; that is to say, it is a way of syn- 

 thesising lipids like carotene, vitamin A and others which 

 are very important biologically and very widely distributed 

 throughout living nature. 



J. D. BernaP'^ has recently put forward the opinion that 

 the lipids must have arisen at a comparatively late stage in 

 organic chemical evolution. It seems to me that, on the 

 contrary, the reduced conditions on the surface of the 

 primaeval Earth were especially favourable for the formation 



