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MHTCET 10 May 2024 Shift 2 Paper

Question : 56 of 150

Marks: +1, -0

$C_{4} \mathrm{H}_{9} \mathrm{OH}+\mathrm{NaBr}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow C_{4} \mathrm{H}_{9} \mathrm{Br}+\mathrm{NaHSO}_{4}+\mathrm{H}_{2} \mathrm{O}$
$C_{2} \mathrm{H}_{4}+\mathrm{H}_{2} \xrightarrow{\mathrm{Ni}} C_{2} \mathrm{H}_{6}$
$C_{2} \mathrm{H}_{5} \mathrm{OH}+C_{2} \mathrm{H}_{5} \mathrm{COOH} \longrightarrow C_{2} \mathrm{H}_{5} \mathrm{COOC}_{2} \mathrm{H}_{5}+\mathrm{H}_{2} \mathrm{O}$
$C_{4} \mathrm{H}_{9} \mathrm{OH}+\mathrm{SOCl}_{2} \xrightarrow{\Delta} C_{4} \mathrm{H}_{9} \mathrm{Cl}+\mathrm{HCl}+\mathrm{SO}_{2}$

Solution:

Concept:

Atom economy measures how much of the starting materials end up in the desired product.

Explanation:

A reaction with high atom economy produces very little waste, which is a key principle of green chemistry.

Option B is an addition reaction: ethene reacts with hydrogen in the presence of nickel to form ethane.

In this reaction, all atoms of the reactants are incorporated into the final product, so no by-product is formed.

Atom economy is calculated using the formula:

\text{Atom economy} = \frac{\text{Molar mass of desired product}}{\text{Total molar mass of reactants}} \times 100

For option B:

C_2H_4 + H_2 \xrightarrow{\mathrm{Ni}} C_2H_6

Molar mass of reactants

= 28 + 2 = 30

Molar mass of product

= 30

\text{Atom economy} = \frac{30}{30} \times 100 = 100\%

Thus, this reaction has the highest atom economy among the given options.

The other options involve substitution or esterification, which produce by-products and therefore have lower atom economy.

Answer:

Option B:

C_2H_4 + H_2 \xrightarrow{\mathrm{Ni}} C_2H_6

exhibits good atom economy.

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