6C.19

Acidity $K_{a}$
Basicity $K_{b}$
The Conjugate Seesaw $K_{a}\times K_{b}=K_{w}$

Amy Luu 2G
Posts: 105
Joined: Wed Sep 18, 2019 12:19 am

6C.19

Which is the stronger base, the hypobromite ion, BrO2, or morphine, C17H19O3N? Justify your answer.
I am unsure of how to approach this problem. Pls provide a detailed explanation thanks!

Hannah Lee 2F
Posts: 117
Joined: Thu Jul 11, 2019 12:15 am

Re: 6C.19

BrO- would be the stronger base because it is the conjugate base of a weak acid, HBrO. A weak parent acid always indicates a strong conjugate base that must be a relatively good proton acceptor, which can relatively easily form HBrO molecules when added to water in the rxn: BrO- + H2O --> HBrO + OH-. On the other hand, C17H19O3N is a very weak base that accepts H+ from the lone pair on N; it undergoes very little disassociation in an aqueous solution.

Fdonovan 3D
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

Re: 6C.19

Hannah Lee 1I wrote:BrO- would be the stronger base because it is the conjugate base of a weak acid, HBrO. A weak parent acid always indicates a strong conjugate base that must be a relatively good proton acceptor, which can relatively easily form HBrO molecules when added to water in the rxn: BrO- + H2O --> HBrO + OH-. On the other hand, C17H19O3N is a very weak base that accepts H+ from the lone pair on N; it undergoes very little disassociation in an aqueous solution.

This makes sense, but how would we know which conjugate acid is stronger just from knowing the formula?

Hannah Lee 2F
Posts: 117
Joined: Thu Jul 11, 2019 12:15 am

Re: 6C.19

You would need to be given the pKa or Ka values to make sure, so if this was given on an exam, you would be provided with that information.