Acid Catalyzed Hydro-alkoxy Addition
Add yours
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.
Ernest Z. · 2 · 4 comments · Dec 13 2014
-
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.
Robb G.
·
1
·
4
comments
·
Jan 20 2015
-
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.
- Protonation of the alkene to create reaction conditions in which an alcohol can be a good nucleophile.
- Nucleophilic backside-attack of the carbocation intermediate.
- Removal of the attached alkoxide's proton (
#"pKa" ~~ -3.6# ) to regenerate the catalyst and form the product(s).
Truong-Son N. · 1 · 9 comments · Nov 17 2015
Questions
Videos on topic View all (2)
Alkene and Alkyne Addition Reactions
-
1Carbocation & Markovnikov's Rule
-
2Hydrohalogenation
-
3Halogenation
-
4Acid Catalyzed Hydration
-
5Acid Catalyzed Hydro-alkoxy Addition
-
6Hydration via Hydroboration-Oxidation
-
7Epoxidation
-
8Osmylation-OsO4 (Osmium Tetroxide)
-
9Ozonolysis
-
10Hydrogenation
-
11Introduction to Reactions and Mechanisms