Question

Choose the incorrect options. (A) If initial mixture of \(\mathrm{P}, \mathrm{Q}\) and R containing 1 mole of each is reacted with excess Na metal, then 2 mole of \(\mathrm{H}_{2}\) gas will evolve (B) First \(\mathrm{H}_{2} \mathrm{O}\) layer contains (C) (P), (Q), (R) have common name aniline, benzoic acid and carbolic acid respectively. (D) Correct basic strength: \(o\)-toluidine \(>(\mathrm{P})>(\mathrm{P})^{\prime}\)

Short answer

The incorrect options are (A) and (B). Statement (A) is incorrect because 1.5 moles of H2 gas evolve instead of 2 moles when each of the compounds is reacted with excess Na metal. Statement (B) is incomplete, making it impossible to analyze and determine its correctness.

Step-by-step solution

Statement (A) analysis

To analyze statement (A), we need to consider the reaction of each of the three compounds with excess Na metal and check if 2 moles of H2 gas will evolve. Aniline, benzoic acid, and carbolic acid can be represented as \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{NH}_{2}\), \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{COOH}\), and \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{OH}\). All of these compounds contain hydrogens that can be replaced by sodium to form H2 gas. Let's write the reaction for each of them. Aniline + Na → \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{N}_{2}\mathrm{Na} + \dfrac{1}{2}\mathrm{H}_{2}\) (1) Benzoic acid + Na → \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{COONa} + \dfrac{1}{2}\mathrm{H}_{2}\) (2) Carbolic acid + Na → \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{ONa} + \dfrac{1}{2}\mathrm{H}_{2}\) (3) Summing all these three reactions: P + Q + R + 3Na → \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{N}_{2}\mathrm{Na}+\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{COONa} + \mathrm{C}_{6}\mathrm{H}_{5}\mathrm{ONa} +\dfrac{3}{2}\mathrm{H}_{2}\) From the above reaction, we can see that 1.5 moles of H2 gas will evolve, not 2 moles, as claimed by statement (A). Hence, statement (A) is incorrect.

Statement (B) analysis

Statement (B) mentioned that the first H2O layer contains. However, it didn't mention what this layer contains, so we cannot analyze this statement due to incomplete information.

Statement (C) analysis

Statement (C) states that compounds P, Q, and R have the common names aniline, benzoic acid, and carbolic acid, respectively. This statement is in accordance with the chemical formulas provided above, so statement (C) is correct.

Statement (D) analysis

Statement (D) states the correct basic strength as: \(o\)-toluidine \(>(\mathrm{P})>(\mathrm{P})^{\prime}\). This seems to be a ranking of the compounds in terms of their basic strength, although there is a typographical error that repeats P. But it seems reasonable to assume that it is meant to represent P, Q, and R in that order. As aniline (P) and carbolic acid (R) are both bases, and benzoic acid (Q) is an acid, it is reasonable to expect the basic strength of aniline and carbolic acid to be greater than that of benzoic acid. Hence, statement (D) is correct. Conclusion: Incorrect options are (A) and (B). The reason being: Statement (A) is incorrect because 1.5 moles of H2 gas evolve, not two, when each of the compounds is reacted with excess Na metal, and statement (B) is incomplete, making it impossible to analyze and determine its correctness.

Key concepts

Basic Strength

In organic chemistry, the basic strength of a compound refers to its ability to accept protons. It's an important concept when analyzing compounds like aniline and their comparison with acids such as benzoic acid.

• Aniline: Aniline (\(\text{C}_6\text{H}_5\text{NH}_2\)) is an aromatic amine and exhibits basic characteristics due to the presence of the amino group attached to the benzene ring. The nitrogen atom in the amino group has a lone pair of electrons, which can accept protons, making aniline a base.
• Benzoic Acid: This compound (\(\text{C}_6\text{H}_5\text{COOH}\)) is not a base but an acid. The carboxyl group renders it acidic, as it donates protons instead of accepting them, contrary to aniline.
• Carbolic Acid: Also known as phenol (\(\text{C}_6\text{H}_5\text{OH}\)), this compound is weakly acidic. It's less acidic than benzoic acid but can donate protons, distinguishing it from bases.

To sum it up, when comparing the basic strength of these compounds, aniline stands out as the base among them, with the others typically donating protons in reactions.

Reaction with Sodium Metal

When organic compounds react with sodium metal, hydrogen gas is often a byproduct. This is a common test to evaluate the reactivity of various functional groups in organic chemistry.

• Aniline Reaction: Aniline reacts with sodium, evolving hydrogen gas. The reaction can be represented as:\[\text{C}_6\text{H}_5\text{NH}_2 + \text{Na} \rightarrow \text{C}_6\text{H}_5\text{NHNa} + \dfrac{1}{2} \text{H}_2\]This showcases aniline's ability to react with metals and release \(\text{H}_2\) gas.
• Benzoic Acid Reaction: For benzoic acid, the reaction with sodium leads to the formation of sodium benzoate and again releases hydrogen gas:\[\text{C}_6\text{H}_5\text{COOH} + \text{Na} \rightarrow \text{C}_6\text{H}_5\text{COONa} + \dfrac{1}{2} \text{H}_2\]
• Carbolic Acid Reaction: Similarly, carbolic acid reacts with sodium to yield sodium phenoxide and hydrogen gas:\[\text{C}_6\text{H}_5\text{OH} + \text{Na} \rightarrow \text{C}_6\text{H}_5\text{ONa} + \dfrac{1}{2} \text{H}_2\]

Each of these reactions contributes to a total release of 1.5 moles of \(\text{H}_2\) gas, assuming 1 mole of each starting compound.

Aniline, Benzoic Acid, Carbolic Acid

Aniline, benzoic acid, and carbolic acid are common compounds with distinct characteristics in organic chemistry.

• Aniline: Known for its aromatic amine structure, aniline has industrial significance in dye manufacturing. Its benzene ring and amino group define its basic properties.
• Benzoic Acid: This is a simple aromatic carboxylic acid used mainly as a food preservative. Its acidic nature arises from the carboxyl group (\(\text{COOH}\)).
• Carbolic Acid: Also referred to as phenol, this compound serves as an early antiseptic. Phenol is less acidic than carboxylic acids but can donate protons due to its hydroxyl group (\(\text{OH}\)).

These compounds illustrate varied reactivity and functional group behaviors, making them essential topics in learning about organic chemistry reactions.