Acid Catalyzed Alkoxylation
4:37 — by Jules B.

Tip: This isn't the place to ask a question because the teacher can't reply.

## Key Questions

• An acid catalyzed hydro-alkoxy addition is the addition of an alcohol to a C=C double bond to form an ether.

An example is the addition of methanol to 2-methylpropene to form t-butyl methyl ether.

This is an electrophilic addition reaction.

In Step 1, a hydronium or oxonium ion is attacked by the π bond.

In Step 2, the alcohol attacks the carbocation and forms an oxonium ion.

In Step 3, the alcohol deprotonates the oxonium ion to form the ether.

Here’s a video on the addition of alcohols to alkenes.

• One adds an alcohol like H-OCH3 to result in an ether, one adds a water to add an alcohol group.

For example, with double bond reactions, you can add H3O+ alone or you can add H2O using Hg(OAc)2, THF, followed up with NaBH4.

For adding an alkoxy group to a double bond, you don't usally add a protonated HOCH3 but instead add it with Hg(OAcF3), THF. I have never seen acid catalyzed alkoxylation to a double bond but I suppose it is possible.

• The acid-catalyzed alkoxylation is an analogous reaction to the acid-catalyzed hydration (Markovnikov addition of water via acid catalysis), and can go as follows for a substituted alkene and a generic alcohol:

where the racemic mixture of the major or minor products can be written as a line bond instead of both the hash and wedge bonds.

(Had it not been racemic but uneven, a squiggly bond would have been the way to write it.)

The mechanism would go as follows:

with Markovnikov addition giving the major product.

1. Protonation of the alkene to create reaction conditions in which an alcohol can be a good nucleophile.
2. Nucleophilic backside-attack of the carbocation intermediate.
3. Removal of the attached alkoxide's proton ($\text{pKa} \approx - 3.6$) to regenerate the catalyst and form the product(s).

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