Question

Determine the product formed when $3-\mathrm{bromo}-2,2-\mathrm{dimethylbutane}$ reacts with Ethanol at high temperatures.

• A. $2,3-dimethylbut-2-ene$
• B. $3,3-dimethylbut-1-ene$
• C. $3-ethoxy-2,2-dimethylbu\tan e$
• D. $2-ethoxy-2,3-dimethylbu\tan e$

Answer 1

The correct option is A

$2,3-dimethylbut-2-ene$

1) Structures of $\mathbf{3}\mathbf{-}\mathbf{bromo}\mathbf{-}\mathbf{2}\mathbf{,}\mathbf{2}\mathbf{-}\mathbf{dimethylbutane}$ and Ethanol:

and

2) Reaction between $\mathbf{3}\mathbf{-}\mathbf{bromo}\mathbf{-}\mathbf{2}\mathbf{,}\mathbf{2}\mathbf{-}\mathbf{dimethylbutane}$ and Ethanol at high temperature:

The reaction between $3-\mathrm{bromo}-2,2-\mathrm{dimethylbutane}$ and Ethanol at high temperature involves the following 3 steps.

Step 1: Formation of a carbocation:

In the first step, the Carbocation is formed at ${\mathrm{C}}_3$ carbon due to the elimination of Bromine.

Step 2: Shifting of methyl groups from ${\mathbf{C}}_{\mathbf{2}}$ to ${\mathbf{C}}_{\mathbf{3}}$:

After the formation of Carbocation, the methyl group from ${\mathrm{C}}_2$ carbon shifts to ${\mathrm{C}}_3$ carbon.

Step 3: Removal of Hydrogen ion from ${\mathbf{C}}_{\mathbf{3}}$Carbon:

After the methyl group shift, deprotonation takes place. Resulting in the formation of $2,3-\mathrm{dimethylbut}-2-\mathrm{ene}$.

$\therefore$When $3-\mathrm{bromo}-2,2-\mathrm{dimethylbutane}$ and Ethanol reacts at a high temperature, $2,3-\mathrm{dimethylbut}-2-\mathrm{ene}$ is formed as a product.

Hence, option A is correct.