462 Transactions. — Chemistry and Physics, 



This alcoholic constitution is, I believe, at present not 

 generally accepted, but it is probable that in phenol solution 

 the molecules join up with themselves to give an alcohol, for 

 (a) the alcohols have a molecular depression increasing with 

 the concentration ; (b) the alcohols have a high initial mole- 

 cular depression. 



Hippuric acid has already been discussed : it possesses 

 a resemblance to levulinic acid only in that there exists a 

 carboxyl group in the molecule. 



The Connection between the Rate of Association and 

 other Properties of the Acids. 



Sudborough and Lloyd* have determined the rates of 

 esterification of a number of substituted acetic acids in the 

 presence of hydrochloric acid. The qualitative agreement 

 between their results and those in Table II. is remarkable. 

 The comparison is shown in the following table : — 



For the esterification constant the numbers are given in 

 decreasing order. With the single exception of propionic acid 

 the values for the rate of association are in exactly the same 

 order. 



The reason of this is not far to seek. The most probable 

 theory of esterification is due to Henry : his explanation is 

 based on an additive hypothesis. This is what occurs with 

 the acids in phenol solution ; but in this case like molecules 

 are added together, while in the process of esterification an 

 unstable addition product is formed with the alcohol, and this 

 immediately decomposes into the ester. 



Looking somewhat ahead, it is to be expected that the 

 ortho acids will associate less rapidly than their isomers, as 

 these compounds are the most difficult to esterify. Further, 

 the diortho substituted acids should scarcely associate at all, 

 as, according to the well-known researches of V. Meyer and 

 his pupils, these acids either do not form esters by this method 

 or do so only with the greatest difficulty. Whether this sup- 

 position is true or false I hope to ascertain in the near future. 



* Trans. Chem. Soc, 1899, 467. 



