Esterification - SN1 or SN2

[crays]

Hi guys, i have a question, is the process of esterification a bimolecular or unimolecular nucleophilic substitution process?

 

[Ygggdrasil]

If a reaction occurs via a SN1 mechanism, a carbocation intermediate will be formed. What carbocation would be formed if esterificaiton occured via an SN1 reaction? Would this be a particularly stable carbocation?

For reaction to occur via an SN2 reaction, the reaction requires a good nucleophile and it requires that the nucleophile not be sterically hindered from reacting with the electrophile. Is this true for an esterification reaction?

 

[crays]

after thinking about it, i think it should be of SN2 because the carbocation is not stable since it only have 2 group of alkyl donating to it. While it has a double bond O, it should have sufficient space for SN2 to occur. But am i right?

 

[Ygggdrasil]

Yup. Esterification will definitely be a bimolecular reaction because the OH group would be unlikely to dissociate and form a carbocation for the reasons you stated above.

Now the mechanism is slightly different from the standard SN2 reaction which proceeds via the formation of a pentavalent transition state. Fischer esterification involves the formation of a tetrahedral intermediate (refered to as the activated complex in the wikipedia article) (http://en.wikipedia.org/wiki/Fischer_esterification).

Now, I should also mention that I'm speaking about Fischer esterification. There are many other types of esterification reactions which do occur via SN2 reactions, but there may be some other types of esterification reactions that do not involve SN2 reactions.

 

[crays]

Thanks a bunch for the answer =D