Question

Which of the following is gem-dihalide?

• A. ${\mathrm{CH}}_3{\mathrm{CHBr}}_2$
• B. ${\mathrm{BrCH}}_2{\mathrm{CH}}_2\mathrm{Br}$
• C. ${\mathrm{CH}}_3{\mathrm{CHBrCH}}_2\mathrm{Br}$
• D. ${\mathrm{CH}}_3{\mathrm{CHBrCH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}$

Answer 1

The correct option is A

${\mathrm{CH}}_3{\mathrm{CHBr}}_2$

Explanation for correct option:

A. ${\mathrm{CH}}_3{\mathrm{CHBr}}_2$

Geminal dihalides:

• It is a di-halo compound.
• "In geminal dihalides, the halogen atoms are present on the same carbon atom.
• “In vicinal dihalides, the halogen atoms are present on the adjacent carbon atoms.”
• For example, $1,1$-Dichloroethane is a geminal dihalide while $1,2$-Dichloroethane is a vicinal dihalide.

$1,1$-Dibromoethane $\left({\mathrm{CH}}_3{\mathrm{CHBr}}_2\right)$ is a geminal dihalide as both the halogen are present on the same carbon atom.

Explanation for incorrect options:

B. ${\mathrm{BrCH}}_2{\mathrm{CH}}_2\mathrm{Br}$

It is a vicinal dihalide as the halogen atoms are present on the adjacent carbon atoms.

C. ${\mathrm{CH}}_3{\mathrm{CHBrCH}}_2\mathrm{Br}$

It is a vicinal dihalide as the halogen atoms are present on the adjacent carbon atoms.

D. ${\mathrm{CH}}_3{\mathrm{CHBrCH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br}$

It is not a vicinal dihalide as the halogen atoms are not present on the adjacent carbon atoms.