Deuterium oxide (D2O) is water in which the protons (1H) have been replaced by their heavier isotope deuterium (2H). It is readily available and is used in a variety of mechanistic studies in organic chemistry and biochemistry. When D2O is added to an alcohol (ROH), deuterium replaces the proton of the hydroxyl group.
ROH + D2O ⇌ ROD + DOH
The reaction takes place extremely rapidly, and if D2O is present in excess, all the alcohol is converted to ROD. This hydrogen–deuterium exchange can be catalyzed by either acids or bases. If D3O+ is the catalyst in acid solution and DO- the catalyst in base, write reasonable reaction mechanisms for the conversion of ROH to ROD under conditions of (a) acid catalysis and (b) base catalysis.