Dear M. U. Khan

I think it is obvious that the acid medium used will diminish the ability of methanol (the protic solvent)to form hydrogen bonding which is the main reason of it's difference over the aprotic solvent ,acetonitrile.Then both solvents have a methyl group(one carbon )in addition to the functional group (-OH,-CN),and the original competition arises from the activity of certain group which in this case ,no big difference seemed after,say the protonation of alcohol in an acidic medium.

Thanks

because a proton can not participates in reaction

• rotic solvents have O-H or N-H bonds. Why is this important? Because protic solvents can participate in hydrogen bonding, which is a powerful intermolecular force. Additionally, these O-H or N-H bonds can serve as a source of protons (H+).
• Aprotic solvents may have hydrogens on them somewhere, but they lack O-H or N-H bonds, and therefore cannot hydrogen bond with themselves.

For the average first semester student, these distinctions come up the most in substitution reactions, where hydrogen bonding solvents tend to decrease the reactivity of nucleophiles; polar aprotic solvents, on the other hand, do not.There are 3 types of solvents commonly encountered: nonpolar, polar aprotic, and polar protic. (There ain’t such a thing as a non-polar protic solvent).