Question

The product $\mathrm{Q}$ in the following reaction sequence is $\frac{{\mathrm{NaNO}}_2}{\mathrm{HX}(0-5{)}^{\circ }\mathrm{C}}⟶\mathrm{P}-\frac{\mathrm{B}\text{ oil }}{{\mathrm{H}}_2\mathrm{O}}⟶\mathrm{Q}$

Short answer

In the given reaction sequence, sodium nitrite (NaNO2) reacts with HX at low temperature (0-5°C) in a diazotization reaction, producing a diazonium salt, ${\mathrm{ArN}}_2\mathrm{X}$, as intermediate product P. Next, P reacts with water, undergoing hydrolysis, and produces an aromatic hydroxide, $\mathrm{ArOH}$, as product Q.

Step-by-step solution

Understand the reactants and conditions for producing P

The given reaction sequence begins with sodium nitrite (NaNO2) reacting in the presence of an acidic medium (HX) at low temperature (0-5°C). These conditions suggest a diazotization reaction, a process where a primary aromatic amine (-NH2) reacts with a nitrosating agent (NaNO2) and acid (HX) to produce a diazonium salt.

Identify the intermediate product P in diazotization reaction

In the diazotization reaction, an aromatic amine will react with NaNO2 and HX, resulting in a diazonium salt (ArN2X). The intermediate product $P$ would have the following form: ${\mathrm{ArN}}_2\mathrm{X}$, where "Ar" is the aryl group and "X" is the halide ion from the acidic reagent ($\mathrm{HX}$).

Understand the reactants for producing Q

To produce Q, the diazonium salt P reacts with water and a substance "B oil." The diazonium salt's reaction with water typically replaces the diazonium ion with a hydroxyl group (-OH). This reaction is known as hydrolysis, where the diazo group (N2) is replaced with a new functional group due to the presence of H2O.

Identify the product Q in the hydrolysis reaction

From the hydrolysis reaction, the intermediate product (diazonium salt) will have its diazo group replaced by a hydroxyl group (-OH). As a result, the product Q will have the following form: $\mathrm{ArOH}$, where "Ar" is the aryl group. In conclusion, the product Q in the given reaction sequence is an aromatic hydroxide ($\mathrm{ArOH}$).

Key concepts

Primary Aromatic Amine

A primary aromatic amine is a compound that contains an amino group (-NH2) attached to an aromatic ring, such as benzene. These compounds are typically used as the starting material in diazotization reactions. The aromatic ring provides stability to the amine, which is important when the amino group undergoes further chemical reactions under specific conditions.

Primary aromatic amines are unique because their structure allows them to participate in a variety of chemical reactions, such as coupling with other aromatic compounds or undergoing substitution reactions.

When engaging in a diazotization reaction, a primary aromatic amine reacts with a nitrosating agent like sodium nitrite in the presence of an acid. This prepares the amine to transform into a more reactive intermediate, which is crucial in synthesizing various compounds, including dyes and pharmaceuticals.

Understanding the reactivity of primary aromatic amines is essential in organic chemistry, as it provides insight into their wide range of industrial and laboratory applications.

Diazonium Salt Formation

Diazonium salt formation is a key reaction in organic chemistry, particularly in the synthesis of aromatic compounds. It begins with a primary aromatic amine reacting with sodium nitrite ($\mathrm{NaNO}\mathrm{\_}2$) in an acidic environment at low temperatures (0-5°C). The process transforms the amine into a diazonium salt, characterized by the presence of a diazonium group (N2+).

The reaction conditions are crucial because they stabilize the diazonium ion, which is highly reactive. The diazonium salt $\mathrm{ArN}\mathrm{\_}2\mathrm{X}$, where 'Ar' is the aryl group and 'X' is the counterion from the acid, can then participate in further transformations.

One unique property of diazonium salts is their ability to form various substitution products. Because the diazonium group is a good leaving group, it can be replaced by different nucleophiles, leading to the formation of compounds like phenols ($\mathrm{ArOH}$), halides, or azo dyes. This versatility makes diazonium salts a valuable tool in organic synthesis.

Moreover, their formation and conversion are essential in developing pharmaceuticals, fabrics, and polymers, demonstrating their importance beyond the laboratory.

Organic Hydrolysis Reaction

The organic hydrolysis reaction involving diazonium salts is vital for converting these intermediates into more stable and useful products. In this process, the diazonium salt $\text{(e.g., }\mathrm{ArN}\mathrm{\_}2\mathrm{X}\text{)}$ reacts with water, resulting in the replacement of the diazo group with a hydroxyl group (OH). This reaction is typically carried out with heat and sometimes requires a catalyst.

Hydrolysis of diazonium salts is especially important in converting these reactive intermediates into alcohols, such as aromatic hydroxides ($\mathrm{ArOH}$). During the reaction, the nitrogen is released as nitrogen gas (N2), simplifying the molecular structure and making it more stable.

This kind of hydrolysis finds applications in producing phenolic compounds, which are precursors to resins, drugs, and plastics. It is a straightforward method to introduce a hydroxyl group into an aromatic structure without requiring high energies or complex reagents.

Overall, organic hydrolysis is a practical, efficient reaction in organic chemistry, facilitating the transformation of complex intermediates into simpler, functional compounds.