Organic Chemistry> If CH3OH is more acidic than H2O then met...

If CH3OH is more acidic than H2O then methoxide ion must be a weak base than hydroxide ion, is this possible?

Ankit Dash , 7 Years ago

Grade 12th pass

2 Answers

Arun

Last Activity: 7 Years ago

Dear Ankit

Generally the stronger acid will be that molecule which yields a conjugate base that is the weaker base (less strongly alkaline). If you write out the acidic reactions:

CH3OH CH3O[-] + H[+]

H2O HO[-] + H[+]

Now which is the stronger base, hydroxide or methoxide ion? In this case, hydroxide is the stronger base BECAUSE it does not stabilize the negative charge as well as the methoxide ion does. The negative charge on methoxide can be delocalized (distributed among more atoms) and this represents a form of stabilization.

For this reason, CH3OH can stabilize the loss of a proton more easily, and the ability to stabilize the loss of a proton can increase acidity.

Rajeev

Last Activity: 7 Years ago

water is more acidic than methanol in aqueous medium and other polar sovents. Methoxide ion is a strong base than Hydroxide because methoxide ion is (conjugate base of methanol) is more unstable than Hydroxide. so hydroxide is less basic than methoxide ion. methoxide ion is destabilized by positive inductive effect from alkyl(methyl) group

more over pKa for water is 14 and pKa for mathanol is 15,5 in aqueous medium which clearly says water is more acidic than methanol

when the medium is DMSO ie dimethylsulphoxide methanol behave as more acidic . but generaly we consider aqueous solution for comparison of acidity