Textbook Problem 6C.17

[AustinMcBrideDis3L]

Can someone explain the reasoning behind why the answer is hypobromite?

Which is the stronger base, the hypobromite ion, BrO−, or morphine, C17H19O3NC17H19O3N? Justify your answer.

[gabbi_r2C]

I think this has to do with morphine being a very large molecule that makes it, as a base, fairly stable before receiving an H+ atom (having ot do with many electronegative O atoms distributing charge), so much so that it is more stable than its conjugate acid, while the opposite is true for BrO-.

[Ven Chavez 2K]

In this case, hypobromite ion is a stronger base I believe because it is a conjugate base to the acid HBrO. Since HBrO is not a strong acid then it is a weak acid. From what we are told in class, a weak acid has a strong conjugate base and a weak base has a strong conjugate acid. In the case of morphine, I'm not completely sure but morphine is more than likely at its most stable in the structure its in so it is a weak base.

[Jacquelyn Challis 2B]

the textbook's answer says, "the smaller the pKb of a base, the stronger the base. pKb (morphine)= 5.79. pKb (BrO-)= pKw-pKa=14-8.69=5.31." This reasoning is confusing me because I don't know how they calculated pKb and pKa. Can anyone explain how they got those numbers?