Why don't bromide ions react with methoxide ions?

Question

2012 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-05-31T02:19:13

There are several reasons:

There are several reasons:

1. The two species repel each other.

${CH}_{3} O^{-}$ $"CH"_3"O"^"-"$ has a negative charge — it is not neutral.

Hence, ${Br}^{-}$ $"Br"^"-"$ and ${CH}_{3} O^{-}$ $"CH"_3"O"^"-"$ will repel each other.

2. ${Br}^{-}$ $"Br"^"-"$ is an extremely weak base.

HBr is a very strong acid, so its conjugate base ${Br}^{-}$ $"Br"^"-"$ is an extremely weak base.

${Br}^{-}$ $"Br"^"-"$ has no tendency to remove $H^{+}$ $"H"^+$ from anything.

3. The product of the attack would be quite unstable.

${Br}^{-} + {CH}_{3} O^{-} \to HBr + H - C O^{-}$ $"Br"^"-" + "CH"_3"O"^"-" → "HBr " + "H" stackrel("-")("C")"O"^"-"$

The repulsion between negative charges on adjacent atoms makes the product a high-energy species.