Question

Ethyl bromide can be converted into ethyl alcohol by:
A. Heating with dilute hydrochloric acid and zinc
B. Boiling with an alcoholic solution of \[{\rm{KOH}}\]
C. The action of moist silver oxide
D. Refluxing methanol

Answer 1

Hint: This is a type of nucleophilic substitution reaction of alkyl halides where replacement by hydroxyl groups takes place and alcohols are formed.

Complete Step by Step Solution:
Compounds such as ethyl bromide, which contain one halogen in the molecule are known as mono-halogen compounds. Primary alkyl halides are defined as those compounds in which the halogen atom is linked to a carbon that is linked further to one carbon atom. For example, ethyl bromide \[{\rm{(C}}{{\rm{H}}_3} - {\rm{C}}{{\rm{H}}_{\rm{2}}} - {\rm{Br}})\]. The common name of \[{\rm{C}}{{\rm{H}}_3} - {\rm{C}}{{\rm{H}}_{\rm{2}}} - {\rm{Br}}\]is ethyl bromide and its IUPAC name is bromoethane.

Nucleophilic substitution reactions are those reactions involving the replacement of an ana tom or a group of atoms by a suitable nucleophile. The carbon-halogen bond in alkyl halides is known to be polar because of the greater electronegativity of the halogen as compared to carbon. A nucleophilic attack is possible due to the presence of a partial positive charge on a carbon atom. Thus, when a stronger nucleophile approaches the positively charged carbon of the alkyl halide, the halogen is readily displaced as a halide ion.

Ethyl bromide can be converted to ethanol (ethyl alcohol) by treating silver oxide with water to form silver hydroxide first. When ethyl bromide reacts with the silver hydroxide to give the products as ethanol (ethyl alcohol) and silver bromide.

The possible reactions can be written as shown below:
\[{\rm{A}}{{\rm{g}}_{\rm{2}}}{\rm{O}}\,\,{\rm{ + }}\,\,{{\rm{H}}_2}{\rm{O}} \to {\rm{2AgOH}}\]
\[{{\rm{C}}_2}{{\rm{H}}_5}{\rm{Br}}\,\,{\rm{ + }}\,\,{\rm{AgOH}} \to {{\rm{C}}_2}{{\rm{H}}_5}{\rm{OH}}\,\,{\rm{ + }}\,\,{\rm{AgBr}}\]
Hence, ethyl bromide can be converted to ethyl alcohol by the action of moist silver oxide.
Therefore, option C is correct.

Note: For a given halogen, the boiling point of alkyl halide increases with an increase in the size of the alkyl group. In the case of isomeric halides, the boiling point is known to decrease with branching since surface area decreases with branching. Also, the intermolecular forces of attraction decrease with surface area.