PURDIE'S REACTION 189 



in solution, and it is hence difficult to determine whether an 

 active product is entirely free from the corresponding inactive 

 form. The difficulty was overcome by converting the sup- 

 posedly pure Z-acid, obtained as indicated above, into its 

 methyl ester and alkylating the latter with silver oxide and 

 methyl iodide, whereby methyl Z-methoxypropionate was 

 formed. The latter compound is highly active, and the 

 rotation of the substance so prepared agreeing with that 

 previously determined (Purdie and Irvine (2) ), a strong 

 guarantee of the purity of the Z-acid was furnished. By this 

 procedure experimental error is largely eliminated and traces 

 of inactive material readily detected. 



A number of the esters of the a/3-dimethoxypropionic 

 acid derived from d-glyceric acid have been prepared by 

 Frankland and Gebhard (27) for the purpose of tracing the 

 effect on rotation of replacement by two methyl groups of 

 the two hydroxylic hydrogen atoms in the esters of d-glyceric 

 acid. The methyl, ethyl, propyl, butyl, heptyl, and octyl 

 dimethoxypropionates were obtained by adding silver oxide 

 (3 mols.) to a solution of the corresponding glycerate (1 mol.) 

 and methyl iodide (6 mols. ) in ether. The remaining procedure 

 was as usual. It is worthy of note that these authors refer 

 to the silver oxide reaction as ' the elegant method of alkyla- 

 tion discovered and elaborated by Purdie and his pupils. 

 This reaction is of the very greatest value in alkylating 

 optically active acids. . . .' 



PREPARATION OF MONOALKYLOXY-DERIVATIVES OF 

 Succraic ACID 



Mention has already been made of the preparation of 

 ethyl Z-ethoxysuccinate from ethyl malate by Purdie and 

 Pitkeathly (1), who also obtained Z-ethoxysuccinic acid by 

 hydrolysis of the ester. A detailed study of monomethoxy- 

 succinic acid and its methyl-, ethyl-, and propyl-esters has 



