FUNDAMENTAL CONCEPTIONS 209 



dissociation in other parts of the molecule and especially of hydrogen 

 from carbon must also take place. Consequently the following intra- 

 molecular addition reactions finally occur spontaneously: 

 H 



active trimethylene propylene 



particles 



0- O- 



I I II 



CH, - C - CH, - -> CH, - C - CH 3 -> CH 3 - C - CH S []. 



I I 



H 



active propyleneoxide acetone 



particles [A] 



H 



I I I 



CH 3 -CH-CH-0-^CH 3 CH 2 -CH-O-<=>CH 3 CH 2 -CH:0[]. 



active propyleneoxide 



particles [B] propionaldehyde. 



It is interesting to note that the active B propyleneoxide molecules 

 which are present in smaller ratio suffer rearrangement more readily 

 than the active A molecules. The active C molecules, on the other 

 hand, must be present in far smaller amount and certainly no transfor- 

 mation of propyleneoxide to vinylmethyloxide, CH 2 =CH CH S , 

 takes place. It is important to realize that propyleneoxide, acetone 

 and propionaldehyde are isomers but do not stand in a tautomeric 

 relation to one another. This is also true of trimethylene and propy- 

 lene as well as of a and /? amylene and isoamylene, etc. 



Similarly it can be rigidly shown by experiment that a and /? 



propylidene, CH 3 CH 2 CH= and (CH 3 ) 2 =C(^ , which are sponta- 



neously combustible substances not capable of isolation as such, 

 transform themselves by intramolecular addition, 

 H 



I / I I 



CH,-CH-CH(->CH 3 -CH-CH 2 ;fCH 3 -CH = CH 2 , 



II I I 



and CH 3 C - CH, -H->CH 3 CH - CH 2 ^CH 3 -CH =CH 2 , 



into propylene [non-reversible]. 



There is not the slightest doubt that such intramolecular addition 

 reactions are the basis of the majority of our synthetic methods for 

 making cyclic compounds. The cycloparaffines in Russian petroleum 

 are probably formed from ordinary paraffines by dissociation into 



