Understanding Nitrile Hydrolysis and the Formation of Vinegar

This question asks us to identify a common substance formed through a series of chemical reactions starting with a nitrile. Let's break down the process described:

1. Starting material: A nitrile (R-CN).
2. First reaction: Hydrolysis of the nitrile, giving compound 'X'.
3. Second reaction: Compound 'X' reacts with H⁺ or OH^- to give 'Y'.
4. Final step: 'Y' is diluted to 5-10%, resulting in a known substance.

Step 1: Nitrile Hydrolysis

Nitrile hydrolysis is a reaction where a nitrile is converted into a carboxylic acid or an amide using water, typically under acidic or basic conditions. The reaction proceeds through an amide intermediate.

Under acidic conditions (H⁺):

\(\text{R-CN} + \text{H}_2\text{O} + \text{H}^+ \rightarrow [\text{R-C(OH)=NH}_2]^+ \rightarrow \text{R-CONH}_2 + \text{H}^+\)

Amide Formation (X could be the amide)

\(\text{R-CONH}_2 + \text{H}_2\text{O} + \text{H}^+ \rightarrow [\text{R-C(OH)=NH}_3]^+ \rightarrow \text{R-COOH} + \text{NH}_4^+\)

Carboxylic Acid Formation (Y could be the carboxylic acid)

Under basic conditions (OH^-):

\(\text{R-CN} + \text{H}_2\text{O} + \text{OH}^- \rightarrow [\text{R-C(O}^-)\text{=NH}] \rightarrow \text{R-CONH}_2 + \text{OH}^-\)

Amide Formation (X could be the amide)

\(\text{R-CONH}_2 + \text{OH}^- \rightarrow [\text{R-C(O}^-)\text{NH}_2] \rightarrow \text{R-COO}^- + \text{NH}_3\)

Carboxylate Salt Formation

\(\text{R-COO}^- + \text{H}^+ \rightarrow \text{R-COOH}\)

Carboxylic Acid Formation (Y could be the carboxylic acid after acidification)

From the reaction sequence, it's clear that a carboxylic acid (R-COOH) is the final stable product of complete nitrile hydrolysis, whether through acidic or basic conditions (followed by acidification if needed). The question states 'X' on reaction with H⁺ or OH^- gives 'Y'. This suggests X is an intermediate (like amide) and Y is the final carboxylic acid.

• Let's assume X is the amide (R-CONH₂).
• Reaction of X (amide) with H⁺ or OH^- causes further hydrolysis, yielding the carboxylic acid (R-COOH) and ammonia/ammonium ion. So, Y is the carboxylic acid.

Identifying Compound Y and the Diluted Solution

The question implies a common substance. The simplest and most common carboxylic acid derived from a simple nitrile (like acetonitrile, CH₃CN) is acetic acid (CH₃COOH). If the starting nitrile was acetonitrile, then Y would be acetic acid.

What is a 5-10% solution of acetic acid in water commonly known as?

A 5-10% aqueous solution of acetic acid is the common definition of vinegar.

Checking the Options

1. Wash: This is a general term, not specific to a chemical substance.
2. Azo dye: A class of synthetic organic dyes containing an azo group (-N=N-). Unrelated to nitrile hydrolysis products.
3. Rectified spirit: This refers to ethanol (ethyl alcohol) that has been purified by repeated distillation, typically containing about 95-96% ethanol.
4. Vinegar: This is an aqueous solution of acetic acid, usually 5-10% by volume. This perfectly matches our identification of Y as acetic acid and the final step of dilution.

Therefore, the substance referred to is vinegar.

Conclusion

Nitrile hydrolysis leads to the formation of carboxylic acids. If the starting nitrile is acetonitrile (CH₃CN), the carboxylic acid formed is acetic acid (CH₃COOH). A 5-10% solution of acetic acid in water is known as vinegar.

Revision Table: Key Concepts

Additional Information: Uses of Acetic Acid and Vinegar

Acetic acid is a weak acid with many uses. Concentrated acetic acid is called glacial acetic acid. Vinegar is used widely in cooking, pickling, and cleaning due to its acidity. Acetic acid is also used in the production of polymers like polyvinyl acetate and cellulose acetate, as well as in the manufacture of photographic film and textiles. Nitriles themselves are important intermediates in organic synthesis.