Question

Reaction of which among the following ethers with HI in cold leads to formation of methyl alcohol?
A.Ethyl methyl ether
B.Methyl propyl ether
C.Isopropyl methyl ether
D.Tert-butyl methyl ether

Answer 1

We have to remember that methanol, also called methyl alcohol. It is a light, acidic, has no colour, flammable liquid with a distinctive odour like ethanol.
We need to know that the ethers are a class of organic compounds containing an ether group, an atom of oxygen linked to two groups of alkyl or aryl. They have the general R-O-R' formula, where the alkyl or aryl groups describe R and R'.

Complete step by step answer:
We have to remember that the methyl alcohol is formed by the reaction of tertiary butyl methyl ether with HI. We can write the chemical equation for this chemical reaction as,
${(C{H_3})_3}C - O - C{H_3}\xrightarrow{{HI}}{(C{H_3})_3}C - I + C{H_3}OH$
This reaction follows the $S{N_1}$ mechanism.
HI is the catalyst used in the reaction. The temperature is cold. When ethers are reacted with HI in cold temperature a cation is formed. This cation is reacted with HI which leads to the formation of methyl alcohol.
A step-by-step process is followed by the $SN_1$ reaction mechanism in which the carbocation is first formed from the removal of the leaving group. Then the carbocation of the nucleophile is attacked. Finally, to provide the necessary product, the deprotonation of the protonated nucleophile takes place.
And hence option D is the correct option.

Additional information:
The reaction requires a carbocation intermediate and is usually seen in secondary or tertiary alkyl halide reactions with secondary or tertiary alcohols under strongly basic conditions or under strongly acidic conditions. The alternate $SN_2$ reaction happens with primary and secondary alkyl halides. The $SN_1$ reaction is also regarded as the dissociative process in inorganic chemistry. The cis effect well-describes this dissociation pathway.

Note:
We must remember that the diatomic molecule and halide of hydrogen is hydrogen iodide. Hydroiodic acid or hydroiodic acid, a solid acid, are referred to as aqueous solutions of HI. However, hydrogen iodide and hydroiodic acid differ in that under normal conditions, the former is a gas, while the other is an aqueous gas solution.