Note : In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
Assertion : Ethanol is a weaker acid than phenol.
Reason : Sodium ethoxide may be prepared by the reaction of ethanol with aqueous NaOH.
Now if we look we might think what is an acid?
A simple comparative statement would be a substance is said to more acidic if it de-protonates more easily, or in other words it can release H+ easily. After the loss of a H+ if one molecule is more stable than the other then it is said to be more acidic.
Now taking phenol(C6H5OH).
If it loses a H+ it turns into phenoxide ion(C6H5O-).Now, this phenoxide ion is stabilized due to resonance due to the delocalization of the negative charge on the entire ring. A resonance stabilized molecule is said to be highly stable.
Now in ethanol(C2H5OH), after de-protonation, ethoxide ion is produced(C2H5O-).
Instead of stabilizing , due to the inductive effect of the bulky ethyl groups the ethoxide ion gets destabilized. If an electron withdrawing group(-NO2,CN) was present then it would have been stabilized to some extent but as we know resonance stabilization provides much more stability than inductive effect.
As a result of which ethanol is less acidic.
