Question

Write the equation of the reaction of hydrogen iodide with (i)1-propoxypropane (ii) methoxybenzene and (iii) benzyl ethyl ether.

Answer 1

Hint: When ethers heated in presence of HI it dissociates into alcohol and alkyl iodide. Ether is a compound where two alkyl or aryl or one alkyl and one aryl group is bonded with oxygen. It can be formed by the dehydration of alcohols by emitting water molecules using dehydrating agents like Conc.

Complete step by step answer:
In presence of an acid, ether can be dissociated. For example, in the presence of HI, it dissociates by the following mechanism.
 \[ROR'\xrightarrow{{HI}}ROH + R'I\xrightarrow{{HI}}RI + R'I\]
 

This mechanism is the \[S{N^2}\] mechanism. The formation of alkyl iodide and alcohol depends upon the group attached to the oxygen. Between secondary and Primary alkyl groups, the primary alkyl group favors the \[S{N^2}\] attack at the iodide nucleophile to form corresponding alkyl iodide. Between secondary and tertiary alkyl groups, the secondary alkyl group favors the \[S{N^2}\] attack at the iodide nucleophile to form corresponding alkyl iodide. And between tertiary and Primary alkyl groups, the primary alkyl group favors the \[S{N^2}\] attack at the iodide nucleophile to form corresponding alkyl iodide. In between the vinyl or benzyl group and an alkyl group, the alkyl group favors the \[S{N^2}\] attack at the iodide nucleophile to form corresponding alkyl iodide. Because vinyl and benzyl groups do not participate in the \[S{N^2}\] reaction.
Now for 1-propoxypropane in presence of HI, it will dissociate in the following manner,

Therefore, on the heating of phenyl methyl ether in presence of propanol is formed with propyl iodide.
Now for the phenyl methyl ether or methyl benzene in presence of HI, it will dissociate in the following manner,

Therefore, on the heating of phenyl methyl ether in presence of phenol is formed with methanol.
Now for the phenyl ethyl ether or ethoxy benzene in presence of HI, it will dissociate in the following manner,

Therefore, on the heating of phenyl ethyl ether in presence of phenol is formed with ethanol.

Note: Ether undergoes combustion reaction, reacts with oxygen, and forms carbon dioxide and water. It is highly flammable and reacts with halogens like chlorine or bromine to form halogen-substituted ether that undergoes substitution reaction in the absence of sunlight.
It is used as a solvent in laboratories and an excellent solvent for dyes, alkaloids, oils, fats, etc. as it can readily dissolve polar as well as non-polar organic compounds. It is also used as an anesthetic due to its high therapeutic index.