Problem 76 - A Complete Resource Book in Chemistry for JEE Main

Question

A fruity smell is produced by the reaction of \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) with (a) \(\mathrm{PCl}_{5}\) (b) \(\mathrm{CH}_{3} \mathrm{COOH}\) (c) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) (d) none of these

Step-by-Step Solution

Answer

The fruity smell is produced with \( \mathrm{CH}_{3} \mathrm{COOH} \).

Step 1: Understanding the Reaction

We first need to understand the reactions that occur between ethanol, \(\mathrm{C}_{2} \mathrm{H}_{5}\mathrm{OH}\), and the given compounds. A fruity smell is most associated with the production of esters.

Step 2: Reaction with \(\mathrm{PCl}_5\)

When \( \mathrm{C}_{2} \mathrm{H}_{5}\mathrm{OH} \) reacts with \( \mathrm{PCl}_5 \), it forms \( \mathrm{C}_{2} \mathrm{H}_{5}\mathrm{Cl} \) (chloroethane) and does not produce a fruity smell.

Step 3: Reaction with \(\mathrm{CH}_{3} \mathrm{COOH}\)

Ethanol reacting with acetic acid, \( \mathrm{CH}_{3} \mathrm{COOH} \), forms an ester \( \mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5} \) (ethyl acetate), which is known for its fruity odor.

Step 4: Reaction with \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\)

Ethanol does not react with acetone \( \mathrm{CH}_{3} \mathrm{COCH}_{3} \) in a way that produces a compound with a fruity smell.

Step 5: Final Conclusion

The reaction producing a fruity smell is only with \(\mathrm{CH}_{3} \mathrm{COOH}\), as it forms an ester (ethyl acetate) with ethanol, which has a distinctive fruity odor.

Key Concepts

Ethanol

Ethanol, often simply referred to as alcohol, is a volatile, flammable liquid widely used both in industrial applications and consumer products.

• It is represented by the chemical formula \( \mathrm{C}_{2} \mathrm{H}_{5}\mathrm{OH} \) and is a key player in many chemical reactions.
• In its pure form, ethanol is used as a solvent and in the synthesis of other organic compounds.

Ethanol also finds application in short-chain esterification processes like the creation of ethyl acetate, a compound with a characteristically pleasant, fruity odor.

Uses of Ethanol

While ethanol is familiar as a component in alcoholic beverages, it also serves as a fuel additive and a precursor in chemical syntheses. To create esters, ethanol can react with acids under the right conditions, producing compounds that often have distinct, pleasant aromas.

Acetic Acid

Acetic acid is an organic compound with the formula \( \mathrm{CH}_{3} \mathrm{COOH} \), known for giving vinegar its sour taste and pungent smell.

• It plays a crucial role in esterification processes, where it reacts with alcohols like ethanol.
• The reaction it undergoes with ethanol is a classic example of an esterification reaction that yields ethyl acetate.

This reaction is typically catalyzed by an acid, which speeds up the process and helps in reaching equilibrium faster.

Importance in Esterification

Esterification is a key chemical reaction in making esters. Acetic acid's ability to form bonds with ethanol results in the desirable ethyl acetate.This process is essential not only in industrial chemistry but also in creating scented products and flavorings. The fruity smell produced by this ester is a testament to the versatility of acetic acid in commercial products.

Ethyl Acetate

Ethyl acetate is a sweet-smelling organic compound, recognizable by its chemical formula \( \mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5} \).

• It is the product of the esterification reaction between ethanol and acetic acid.
• Known for its pleasant, fruity aroma, ethyl acetate is used extensively in perfumes, flavorings, and as a solvent in industries.

Formation and Properties

In the presence of a catalyst, ethanol and acetic acid undergo a reaction to yield ethyl acetate, which can be identified by both its smell and volatilization properties. This reaction not only highlights the utility of esters in everyday life but also underscores their role in industrial applications. Ethyl acetate's low toxicity and agreeable scent make it a staple in formulations where both safety and sensory appeal are key.