# SN1, SN2 or acid-base reaction

I am asked to give the type of reaction (SN1, SN2 or acid-base reaction) for the following reactions. I know that both $\ce{MeOH}$ and $\ce{EtOH}$ polar protic solvents, so because the first is an SN2 reaction shouldn't the second reaction be that as well? It says that it is an acid-base reaction as $\ce{MeO-}$ reacts with the $\ce{EtOH}$ to from 1-bromopropane, $\ce{MeOH}$ and $\ce{EtO-}$ and then goes on to from a SN2 reaction.

I would appreciate if someone could explain why the second reaction would be an acid-base reaction at first instead of a SN2 reaction.

• EtO- would be more basic than MeO-...the proton xfer is fast – Eashaan Godbole Apr 17 '18 at 15:38
• Note: $\ce{MeO-}$ is a strong base while, $\ce{EtOH}$ is a weak base. My question: how can you perform an acid-base neutralisation reaction then? + acid-base neutralistion also produces water as a product! – Rahul Verma Jun 16 '18 at 15:42

## 1 Answer

In both cases the alkoxide will be in an equilibrium with the alcohol. This will be occurring on a faster timescale than the substitution but in the first case it's irrelevant as the same species are present on either side of the equilibrium.

Methanol is more acidic than ethanol, however, so the reaction lies in favour of methoxide and ethanol.

• But EtOH is in vast excess so you are going to end up with EtO- – Waylander Jul 16 '18 at 17:00