CHEMISTRY OF EPINEPHRINE 79 



PHYSICAL PROPERTIES 



Epinephrine is a white, micro-crystalline, hygroscopic com- 

 pound which rapidly decomposes when exposed to the air. 135 

 Ultraviolet light, particularly, hastens its oxidation. Herme- 

 tically sealed, however, it may be permanently stored. Epi- 

 nephrine melts with decomposition at about 216° or at 263° on 

 Maqnenne's block. The natural epinephrine is levorotatory, 

 (a)™* being variously given by different authors, as -50.72° 

 to -53.3°. 



Epinephrine is scarcely soluble in water, a saturated solu- 

 tion containing 0.095 milligrams per cc. at 20° to 25°. It is 

 practically insoluble in alcohol and insoluble in chloroform, 

 petroleum ether, benzol, or ether. 138 



Despite the relative insolubility of epinephrine in water, 

 aqueous solutions of certain salts have a marked solvent ac- 

 tion, (e.g., the borates) and epinephrine hydrochloride itself 

 exerts such an action. The phenolic groupings of epinephrine 

 form water-soluble salts with strong alkalies. The alkaline 

 carbonates or ammonia can not effect this salt formation and 

 hence may be used, as in the isolation of the compound, for 

 precipitating epinephrine as the free base. 



The NH 2 -grouping of epinephrine imparts to it a feebly 

 basic character in virtue of which it forms salts which are 

 readily soluble. Epinephrine hydrochloride, thus formed, is 

 the compound used in medicine. 



CHEMICAL PROPERTIES 



The chemical properties of epinephrine are inherent in the 

 phenolic, alcoholic, and amino groupings which it contains. 

 Like derivatives of catechol (compare, for example, the action 

 of pyrogallol), epinephrine is easily oxidized in neutral or alka- 

 line solution. In fact, epinephrine in aqueous solution is 

 stable only at a pH of 5 or less. In a more alkaline solution 

 oxidation on exposure to air rapidly occurs as evidenced by 

 the gradual change in color of the solution to pink, then red, 



