Why Is Water More Acidic Than Alcohol? Know Science Behind.

Why is water more acidic than alcohol? The strength of acidity of any organic compound depends upon the ease of realizing H+ions and the lat...

Why is water more acidic than alcohol?

The strength of acidity of any organic compound depends upon the ease of realizing H+ions and the latter depends upon the stability of the conjugate base that forms. Any factor that stabilizes the conjugate base of acid increases its acidity.

Mathematically acidity it is compared on the basis of corresponding pKa values. As you have not mentioned particular alcohol assuming it to be methanol. pKa of methanol is 15.5 and that of water is 15.74 and knowing the fact that acidic strength is inversely proportional to pKa values so here methanol is more acidic but this is not the case with other alcohols of higher carbon like ethanol, isopropanol, and so on. 

For example pKa of ethanol is 15.9 and that of tert-butanol is 18. So water is more acidic than tert-butanol. Now, what should be the probable reason behind it, what are the factors that destabilises the conjugate base of tert-butanol.

Two factors that explain 

• We know that positive inductive effect decreases the stability of the conjugate base and in tert-butanol three methyl group increases electron density and hence decreases stability .
• Another reason is salvation. With unhindered alcohol, water molecules can easily surround, solvate, and hence stabilize the alkoxide anion that would form by the loss of the alcohol proton to a base. But if the alkyl group is bulky, the salvation of the alkoxide anion is hindered as in ter-butoxide anion. Stabilization of the conjugate base is not as effective, and consequently, the hindered alcohol is a weaker acid.

This is not the case with water it does not have any alkyl group which is electron realizing in nature.