LEONOR MICHAELIS 



withdrawal of an electron together with a proton; this process is 

 dehydrogenation. The reconciliation with the modern definition is 

 the postulate that only the withdrawal of the electron is characteristic 

 for oxidation, and that the simultaneous detachment of a proton does 

 not belong to the process of oxidation proper. 



The attachment of a proton is termed a change in the level of 

 "acidic ionization." This will become clear if one first considers an 

 example showing the essential features in a very obvious way. Let us 

 start with quinone (I), the reduction of which, according to modern 

 concepts, consists essentially in the attachment of two electrons. The 

 result is formula II, a doubly negatively charged ion of hydroquinone. 



O 



II 

 /\ 



Y 



Quinone 



If the reaction occurs in a strongly alkaline solution, the result of 

 oxidation is molecule II. When the reaction occurs in a less alkaline 

 solution, oipH about 9 to 10, one proton only is attached to II, and the 

 univalent anion of hydroquinone is formed (III). When the reaction 

 occurs in an acid solution, two protons are attached to II, and (union- 

 ized) hydroquinone (IV) is formed. Depending upon the pH, either 

 an electron or a full hydrogen atom may be attached to each oxygen. 

 We now agree on the definition that II, III, and IV are on the same 

 level of oxidation-reduction as, but on lower levels of oxidation than, 

 quinone (I). The diff"erences between II, III, and IV are not in their 

 level of oxidation, but in their level of acidic ionization. 



It is easy to transfer these ideas to the case of the oxidation of 

 alcohol. On detaching two electrons only, one obtains structure V, 

 where two protons exist in the molecule. The two protons, however, 

 are held still less firmly than in hydroquinone ion IV, and under all 



CH3C^H + 

 \OH + 



V 



CH3C' 

 VI 



< 



210 



