Question

Which of the following is an example of Pinnacol-Diazotization?
A.

B.

C.

D.

Answer 1

Hint: The diazotization is the process in which the primary aromatic amine is converted into its diazonium salts. Pinnacol diazotization reaction is processed only in the groups containing alcohol $\left( { - OH} \right)$ group attached with one carbon atom and amino group $\left( { - N{H_2}} \right)$ with another carbon atom.

Complete step by step answer:
First, we will understand the basic steps of the Pinnacol-diazotization reaction. First of all, this reaction is observed in the molecules which contain hydroxyl and amine groups attached to the different carbon atoms. So now we will check all the options one by one to find the reaction which is an example of Pinnacol diazotization reaction. So, let’s start with the first option.
In the first reaction, there is one carbon atom with $\left( { - OH} \right)$ the group but the other carbon atom is attached with bromine which is a halogen. So, this reaction will not satisfy the condition of Pinnacol diazotization.
In the second reaction, there is one carbon atom with $\left( { - OH} \right)$ a group and the other carbon atom is attached with an amine $\left( { - N{H_2}} \right)$. So, this reaction satisfies the condition of Pinnacol diazotization. Therefore, this reaction is an example of Pinnacol diazotization.
In the third reaction both the carbon atoms are attached to the alcohol group $\left( { - OH} \right)$. So this reaction is also not an example of Pinnacol diazotization.
The last reaction does not satisfy the condition of the Pinnacol diazotization reaction. Therefore, this reaction is not an example of Pinnacol diazotization.
Therefore, the correct option is (B).

Note:
In the Pinnacol diazotization reaction the ‘Pinnacol’ represents the oxidation and due to the oxidation of alcohol present on one carbon atom ketone is formed and on the second carbon atom carbocation is formed which undergoes rearrangement.