Question

Heating carvone with aqueous sulfuric acid converts it into carvacrol. The mechanism involves the following steps:

1. The terminal alkene of carvone reacts with acid to form tertiary carbocation 1;
2. A hydride shift results in the formation of tertiary carbocation 2;
3. Deprotonation of the ring leads to conjugated diene 3;
4. Deprotonation at the α carbon leads to the product carvacrol.

Required:
Draw the mechanism and then draw the structure of tertiary carbocation 2.

Answer 1

See figure 1

Step-by-step explanation:

In this question, we have to start with the protonation of the double bond. In carvone we have two double bonds, so, we have to decide first which one would be protonated.

The problem states that the terminal alkene is the one that would is protonated. Therefore, we have to do the protonation in the double bond at the bottom to produce the carbocation number 1. Then, a hydride shift takes place to produce the carbocation number 2. A continuation, an elimination reaction takes place to produce the conjugated diene. Then the diene is protonated at the carbonyl group and with an elimination reaction of an hydrogen in the alpha carbon we can obtain carvacol.