Question

When benzenediazonium chloride is treated with water, the compound formed is (a) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\) (b) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{6}\) (d) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\)

Short answer

The compound formed is \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{OH}\), phenol.

Step-by-step solution

Understanding Benzenediazonium Chloride

Benzenediazonium chloride, with the formula \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{N}_{2}^{+}\mathrm{Cl}^{-}\), is a diazonium salt. These salts are known for their ability to undergo substitution reactions.

Reaction with Water

When benzenediazonium chloride reacts with water, the diazonium group \(\mathrm{N}_{2}^{+}\) is replaced by a hydroxyl group. This reaction typically produces phenol \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{OH}\).

Identifying the Product

The main product of this hydrolysis reaction is phenol. Therefore, after treating benzenediazonium chloride with water, phenol \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{OH}\) is formed.

Conclusion

The reaction of benzenediazonium chloride with water leads to the formation of phenol. Hence, the correct answer is option \((b)\) \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{OH}\).

Key concepts

Hydrolysis of Diazonium Salts

Hydrolysis is a chemical reaction wherein a substance reacts with water, resulting in the decomposition and transformation of the original compound. When it comes to diazonium salts, such as benzenediazonium chloride, hydrolysis involves the replacement of the diazonium group, \(\mathrm{N}_2^+\), with a hydroxyl group (OH). This transformation is crucial in converting the diazonium salt into phenol, \(\mathrm{C}_6\mathrm{H}_5\mathrm{OH}\).

Typically, diazonium chloride is sensitive to water and readily undergoes this hydrolysis to form phenol. The presence of the chloride ion (\(\mathrm{Cl}^-\)) assists in stabilizing the aromatic phenol product. This reaction is primarily favored at warmer temperatures, where the heat facilitates the breaking and reforming of bonds during the process.

Substitution Reactions in Organic Chemistry

Substitution reactions are fundamental in organic chemistry, characterized by the replacement of an atom or a group of atoms in a molecule with different atoms or groups. With benzenediazonium chloride, a classic substitution reaction occurs when the diazonium group (\(\mathrm{N}_2^+\)) is substituted by a hydroxyl (OH) group through hydrolysis to produce phenol.

In substitution reactions, the reactant typically swaps a stable group (like \(\mathrm{N}_2^+\)) with another group, such as an OH group. This exchange maintains the integrity of the aromatic ring while modifying the functional nature of the molecule. As a result, the structure remains stable but acquires new chemical properties, such as the enhanced reactivity or altered solubility that phenol possesses compared to the original diazonium salt.

Phenol Formation

Phenol, \(\mathrm{C}_6\mathrm{H}_5\mathrm{OH}\), is a crucial compound in organic chemistry known for its aromatic properties and its usability in chemical synthesis. The hydrolysis of diazonium salts, like benzenediazonium chloride, results in phenol. This is due to the substitution of the diazonium group by a hydroxyl group in the presence of water.

This conversion is significant because phenol is an important precursor in manufacturing polymers and pharmaceuticals. Through this reaction, a diazonium salt transitions into a more reactive compound with an added hydroxyl group, which can then engage in further chemical reactions. This makes phenol not just a product, but a cornerstone molecular entity in synthesizing various advanced chemical substances.

Diazonium Salts Reactivity

Diazonium salts are renowned for their versatile reactivity, which is crucial in organic synthesis. This reactivity stems from the presence of the diazonium group, \(\mathrm{N}_2^+\), which can be readily replaced during reactions due to its stable nature in aqueous solutions.

Upon exposure to specific reagents like water, the reactivity of diazonium salts becomes evident as they form new compounds like phenol. The ability to reliably undergo predictable substitution reactions makes these salts valuable intermediates. Their reactivity extends beyond hydrolysis and includes variances like coupling reactions to form azo compounds, showcasing their adaptability. These properties make diazonium salts indispensable in creating a wide array of chemical products, keeping them as key players in advanced organic chemistry processes.