Theory of Molecular Volumes. 745 



simple radicles — OCH 3 , — OC 2 H 5 , — OC 3 H 7 ; that is, the 

 elevating influence o£ this more than counterbalances the 

 depressing influences of the latter, 



The Acetic Esters on the other hand show the depressing 

 influence of — OCH 3 , as do the esters of the other fatty acids 

 which include —0 . CH 3 . The remaining part of the curve 

 resembles corresponding curves for the Ethers, which are also 

 distinguished by the presence of an radicle. 



Thus the development of the 

 C radicle is similar in result to the Paraffin curves, 



and the development of the 

 radicle resembles in effect the Ether curves (vide prox.). 



This indicates the importance of the effect of the typical 

 atoms C and 0. 



The Influence of Symmetry. 

 It has been shown that the methyl, ethyl, and probably 

 the propyl salts of the fatty acids have more or less depressed 

 values of V/W ; and this at once introduces the effect of 

 symmetry on molecular volumes. By symmetry we mean 

 the disposition of the C atoms on one side and the other 

 of the typical atom or group — in this case — C — — . 



II 





 Owing to some irregularities in the data, it will be of 

 advantage to read off the values of V/W from the curves. 

 The following numbers indicate the typical effect in the 

 variation in volume with variation in symmetry. 



Isomeric Esters. 



c 8 h,.a. 





M.V. 



B.P. 



Methyl Heptylate, 



C 6 H 13 . CO . OCH 3 



196-2 



173 



Ethyl Caproate, 



5 H U . CO . OC 2 H 5 



1977 



167 



Propyl Valerate, 



C 4 H 9 . CO . OC 3 H 7 



197-8 



167 



Butyl Butyrate, 



C 3 H 7 . CO . OC 4 H 9 



197-8 



165-7 



Hexyl Acetate, 



CH 3 . CO . OC 6 H 13 



197-7 



169 



Heptyl Formate, 



H'.CO.OC~H 1( . 



196-7 



176 





It is seen that the most symmetrical compounds possess 

 the largest volumes and the smallest B.P/s. The volumes 

 fall off towards either end, but more so in the direction of 

 the simplest radicle than in the direction of the simplest 

 C radicle. The boiling-points correspondingly increase. 



