STEREO-CHEMISTRY AND PHYSIOLOGY 475 



the dynamic effects of certain atomic groupings, their influence 

 upon chemical reactions, and similar subjects. In the foregoing 

 pages we have restricted our examination to the first division, 

 and have dealt purely with the question of stereo-isomerism and 

 its connection with the action of certain substances upon living 

 tissues ; but we must now turn to the second part of the subject 

 and discuss the dynamic influence which certain atomic groups 

 may exert upon others. 



When we allow acetic acid to react with ethyl alcohol in 

 pre.«;ence of hydrochloric acid, water is eliminated and ethyl 

 acetate is formed : 



CH^.COOH + C,H,OH = CH3.COOC,H5 + H,0 



Now, the researches of Menschutkin, Sudborough, and Lloyd^ 

 and others ^ have shown that when substituted acetic acids are 

 used instead of the parent substance, the amount of ester formed 

 under given conditions decreases. The amount of this decrease 

 depends on the complexity of the acid, and is quite independent 

 of its strength, as the following table shows : 



Formula of Acid. Amount of Ester. Affinity Constant. 



CH3.COOH 3-661 o-ooi8o 



CHj.CH^.COOH 3-044 000134 



CH3 



\ 



CH . COOH 1-0196 0-00144 



/ 

 CH3 

 CH3 



CH3-C.COOH 0-0909 0.000978 



/ 

 CH3 



A similar decrease in the amount of ester formed is found 

 if the complexity of the alcohol be increased while the acid 

 remains the same throughout, e.g. when acetic acid is esterified 

 with methyl, ethyl, isopropyl, and tertiary butyl alcohols. It is 

 evident, therefore, that the cause of the decrease in the amount 

 of ester formed is to be sought in the change in structure of the 

 acid or of the alcohol. On examining the formulae shown in 

 the table, we find that in each case as we go down the table we 

 are replacing a hydrogen atom by a methyl radicle. In other 



» Menschutkin, Afin. chim. phys. [5], 20, 229 (1880) ; 23, 14 (1881) ; 30, 81 

 ( 883) ; Jourji. Russ. Phys. Chem. Soc. 9, 316, 346 (1877) ; 10, 278 (1878) ; 11, 24, 

 345 (1879); 12, 82 (1880); 13, 564 (1881); 16, 356 (1884); Ber. 13, 1812 (1880); 

 30, 278 1897) ; Annalen der Chem., 195, 334 (1879) ; 197, 193 (1879) -yjourn. Chem. 

 Soc, 8 ,1532 (1906) ; Sudborough and Lloyd, zdid. 75, 467 (1899). 



