Question

Which reagent can be used to convert ethanol to diethyl ether?
(A) $A{{l}_{2}}{{O}_{3}}\text{ at }{{250}^{0}}C$
(B) $\text{conc}\text{.}{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}\text{ at 17}{{\text{0}}^{0}}C$
(C) $\text{conc}\text{.}{{\text{H}}_{2}}\text{S}{{\text{O}}_{4}}\text{ at 130-14}{{\text{0}}^{0}}C$
(D) $A{{l}_{2}}{{O}_{3}}\text{ at 3}{{50}^{0}}C$

Answer 1

Hint: The reaction in which symmetrical ethers are formed is generally the reaction in which alcohol reacts with an acid. For conversion of ethanol to dry ethyl ether 2 moles of ethanol is required.

Complete step by step solution:
In this reaction formation of diethyl ether takes place using concentrated Sulphuric acid. Two moles of ethanol is required to produce one mole of diethyl ether. The reaction takes place in two steps, in the first step molecule of ethyl hydrogen sulphate is formed and in second step diethyl ether is formed and Sulphuric acid is released as a bi product.
The overall reaction involved is:
$2{{C}_{2}}{{H}_{5}}OH\xrightarrow{conc.{{H}_{2}}S{{O}_{4}},130-{{140}^{0}}C}{{({{C}_{2}}{{H}_{5}})}_{2}}O+{{H}_{2}}O$
Mechanism of the above reaction-
The concentrated Sulphuric present at the given temperature range attacks on the ethyl alcohol or ethanol, which leads to the release of one water molecule and molecule of ethyl hydrogen sulphate is formed. The reaction involved is mentioned below:
$2{{C}_{2}}{{H}_{5}}OH+OH-S{{O}_{3}}H\to C{{H}_{3}}C{{H}_{2}}O-S{{O}_{3}}H+{{H}_{2}}O$
Now the product forms in the above reaction i.e. ethyl hydrogen sulphate reacts with one mole of ethyl alcohol or ethanol and will form diethyl ether as the product. During this reaction Sulphuric acid is released as a bi product.
The reaction involved is mention below:
$C{{H}_{3}}C{{H}_{2}}O-S{{O}_{3}}H+S{{O}_{3}}H\to {{({{C}_{2}}{{H}_{5}})}_{2}}O+{{H}_{2}}S{{O}_{4}}$

Hence the correct answer is option (C) i.e. the reagent used to convert ethanol to diethyl ether is Sulphuric acid.

Note: Ethers are basically the derivatives of carbon in which the oxygen atom present is bounded by an alkyl or an aryl group. Ethers are unreactive as compared to alcohols so ethers are generally used as solvents for Fats and oils.