W. A, Drushel — Simple and Mixed Alkyl Phosphates. 647 



observe directly how far the titrations furnished reliable data 

 for calculating the velocity constants for the primary hydrolysis 

 stage. The constants recorded in Table III represent only 

 the primary hydrolysis stage, the latter constants in some cases 

 being perhaps slightly influenced by the secondary reaction. 

 In calculating the constants the reaction was considered of the 

 first order and no account was taken of the possible hydrolytic 

 effect of the very weak dialkyl phosphoric acids set free in the 

 primary hydrolysis stage. The acid hydrolysis was first 

 attempted at 25° but was found to proceed so slowly as to_ 

 make it impracticable at this temperature. A fifth normal 

 solution of trimethyl phosphate in decinormal hydrochloric 

 acid was allowed to stand for thirty-two days at 22° to 25° 

 with an increase of only five per cent in the total acidity of 

 the reaction mixture, and the triethyl ester hydrolyses only 

 about one-fourth as fast. The measurements were therefore 

 made at 100°. 







Table 



III. 









Hydrolysis 



of alkyl phosphates in N/10 



HCl at 100". 





Me 3 P0 4 



600 min. 

 10 5 K 



Et 3 P0 4 



2100 min. 

 10 5 K 



Me 2 EtP0 4 



830 min. 

 10 6 K 



Me 2 PrP0 4 



700 min. 

 10 5 K 



Et 2 PrP0 4 

 I II 

 1770 min. 760 min 

 10 5 K 10 5 K 



209 



50-9 



182 



203 



62-1 



60-9 



215 



51-8 



184 



209 



59-2 



61-5 



224 



50-1 



189 



207 



61-1 



59-5 



. 223 



55-3 



183 



200 



61-6 



6T2 



225 



55-2 



184 



199 



62-1 







55-4 



189 



198 



61-9 





219 53-7 185 202 61-3 60'8 



In this table the ranges of time in minutes through which 

 the titrations were used in the calculation of the constants are 

 given at the top of the columns. In this table of constants 

 the very marked difference in the resistance to hydrolysis of 

 the three alkyl groups, methyl, ethyl and propyl, is noteworthy. 

 The distinct effect of the single alkyl group in the mixed esters 

 upon the rate of hydrolysis is also to be observed. According 

 to Lossen and Kohler's theory, in mixed alkyl phosphates the 

 alkyl group occurring twice is saponified to the exclusion of 

 the single alkyl group. In order to explain the velocity con- 

 stants for the mixed esters on this theory it would be necessary 

 to assume that the presence of the single alkyl group increases 

 the resistance to hydrolysis of the alkyl group occurring twice 

 in the ester. The effect observed is more simply explained by 



