Q42E - Organic Chemistry (Mcmurry)

Question

Question: tert-Butyl ethers can be prepared by the reaction of an alcohol with 2-methylpropene in the presence of an acid catalyst. Propose a mechanism for this reaction

Step-by-Step Solution

Answer

Step 1: Protonation

Protonation is defined as the addition of a proton to an atom, molecule or ion. It is different from hydrogenation because in protonation a change in charge of protonated species occurs, while the charge remain unaffected during hydrogenation. For example formation of ammonium group from ammonia . Protonation is mainly occur in the reaction of an acid with a base to form salt.

Step 2: Protonation of 2-methyl propene

The first step of the reaction is protonation where 2-methylpropene gets protonated with acid to form tertiary carbocation as shown below:

     Protonation of 2-methyl propene by acid

Step 3: Attack on carbocation

In the second step of the reaction oxygen from ROH group attack on carbocation and make bond with the carbon by acquiring positive charge from the carbocation as shown below:

                        Attack of alcohol oxygen on carbocation

Step 4: Loss of proton

In last step of the mechanism deprotonation occurs, tert-butyl ether is formed by the loss of proton.

                                     Formation of tert-butyl ether