Question

Tertiary butyl methyl ether on treatment with HI forms :

• A. Isobutane and Methyl iodide
• B. Isobutanol and Methanol
• C. Tertiary butyl iodide and Methyl iodide
• D. Tertiary butyl iodide and Methanol

Answer 1

The correct option is D

Tertiary butyl iodide and Methanol

Explanation for the correct option:

Option (D): Tertiary butyl iodide and Methanol

• Tertiary butyl methyl ether on treatment with HI forms tertiary butyl iodide and Methanol.
• ${{\mathrm{S}}_{\mathrm{N}}}^1$ mechanism is followed as the tertiary carbonation formed is stable
• The iodide nucleophile gets attached to the tertiary carbon atom to form tertiary butyl iodide and the methyl group that is connected to oxygen form a bond with hydrogen coming from the dissociation of hydrogen iodide to form methanol.
• The equation of the reaction is:

$\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{methyl}\mathrm{ether}}{{\mathrm{CH}}_3-\mathrm{OCH}-{\left({\mathrm{CH}}_3\right)}_3}+\underset{\mathrm{Hyrogen}\mathrm{iodide}}{\mathrm{HI}}\stackrel{}{\to }\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{iodide}}{{\left({\mathrm{CH}}_3\right)}_3-\mathrm{C}-\mathrm{I}}+\underset{\mathrm{Methanol}}{{\mathrm{CH}}_3\mathrm{OH}}$

Explanation for the incorrect options:

Option (A): Isobutane and Methyl iodide

• The molecular formula of isobutane is: $\mathrm{HC}-{\left({\mathrm{CH}}_3\right)}_3$
• The molecular formula of methyl iodide is: ${\mathrm{CH}}_3-\mathrm{I}$
• When Tertiary butyl methyl ether is treated with HI, the following reaction takes place:

$\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{methyl}\mathrm{ether}}{{\mathrm{CH}}_3-\mathrm{OCH}-{\left({\mathrm{CH}}_3\right)}_3}+\underset{\mathrm{Hyrogen}\mathrm{iodide}}{\mathrm{HI}}\stackrel{}{\to }\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{iodide}}{{\left({\mathrm{CH}}_3\right)}_3-\mathrm{C}-\mathrm{I}}+\underset{\mathrm{Methanol}}{{\mathrm{CH}}_3\mathrm{OH}}$

• Hence, Isobutane and Methyl iodide are not formed during the given reaction.
• Therefore, this option is incorrect.

Option (B): Isobutanol and Methanol

• The molecular formula of isobutanol is: ${\left({\mathrm{CH}}_3\right)}_2-\mathrm{CH}-{\mathrm{CH}}_2\mathrm{OH}$
• The molecular formula of methanol is: ${\mathrm{CH}}_3-\mathrm{OH}$
• When Tertiary butyl methyl ether is treated with HI, the following reaction takes place:

$\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{methyl}\mathrm{ether}}{{\mathrm{CH}}_3-\mathrm{OCH}-{\left({\mathrm{CH}}_3\right)}_3}+\underset{\mathrm{Hyrogen}\mathrm{iodide}}{\mathrm{HI}}\stackrel{}{\to }\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{iodide}}{{\left({\mathrm{CH}}_3\right)}_3-\mathrm{C}-\mathrm{I}}+\underset{\mathrm{Methanol}}{{\mathrm{CH}}_3\mathrm{OH}}$

• Hence, Isobutanol and Methanol are not formed during the given reaction.
• Therefore, this option is incorrect.

Option (C): Tertiary butyl iodide and Methyl iodide

• The molecular formula of tertiary butyl iodide is: ${\left({\mathrm{CH}}_3\right)}_3-\mathrm{C}-\mathrm{I}$
• The molecular formula of methyl iodide is: ${\mathrm{CH}}_3-\mathrm{I}$
• When Tertiary butyl methyl ether is treated with HI, the following reaction takes place:

$\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{methyl}\mathrm{ether}}{{\mathrm{CH}}_3-\mathrm{OCH}-{\left({\mathrm{CH}}_3\right)}_3}+\underset{\mathrm{Hyrogen}\mathrm{iodide}}{\mathrm{HI}}\stackrel{}{\to }\underset{\mathrm{Tertiary}\mathrm{butyl}\mathrm{iodide}}{{\left({\mathrm{CH}}_3\right)}_3-\mathrm{C}-\mathrm{I}}+\underset{\mathrm{Methanol}}{{\mathrm{CH}}_3\mathrm{OH}}$

• Hence, Methyl iodide is not formed during the given reaction.
• Therefore, this option is incorrect.

Hence option(d) is the correct option.