Arenes Q13 (with answer explanation)

Based on the molecular formula C8H10 what structural feature might be present in compound B?

• A carboxyl group (-COOH)

• A hydroxyl group (-OH)

• A benzene ring

• An alkene group

Answer explanation

The molecular formula C8H10 suggests a degree of unsaturation. A benzene ring, which contains 6 carbons and 6 hydrogens, accounts for this formula, indicating that compound B likely has a benzene ring as a structural feature.

What type of reaction occurs when compound B reacts with Cl2 in the absence of UV light?

• Nucleophilic substitution

• Free radical substitution

• Electrophilic substitution

• Electrophilic addition

Answer explanation

The reaction of compound B with Cl2 in the absence of UV light is an electrophilic substitution. In this process, the chlorine acts as an electrophile, replacing a hydrogen atom in compound B.

What structural feature of compound B can be deduced from its reaction with Cl2 in the absence of UV light?

• A benzene ring

• A hydroxyl group (-OH)

• A double bond (C=C)

• A halogen atom

Answer explanation

The reaction of compound B with Cl2 in the absence of UV light suggests the presence of a benzene ring, as benzene undergoes electrophilic substitution with chlorine without requiring light, unlike alkenes which would react differently.

What type of reaction occurs when compound B reacts with hot acidified KMnO4?

• Electrophilic addition

• Nucleophilic addition

• Side-chain oxidation

• Free radical substitution

Answer explanation

When compound B reacts with hot acidified KMnO4, it undergoes side-chain oxidation, where the alkyl side chains are oxidized to form carbonyl or carboxylic acid groups, distinguishing it from other reaction types.

What structural feature can be deduced about compound B from its reaction with hot acidified KMnO4?

• Compound B contains a hydroxyl group (-OH)

• Compound B contains an alkyl side chain attached to a benzene ring

• Compound B contains a carboxyl group (-COOH)

• Compound B contains a carbonyl group (C=O)

Answer explanation

The reaction of compound B with hot acidified KMnO4 indicates it can be oxidized, suggesting the presence of an alkyl side chain attached to a benzene ring, as this structure can undergo oxidation to form carboxylic acids.

What type of reaction occurs between compound C and NaOH?

• Acid-base reaction

• Free radical substitution

• Electrophilic addition

• Nucleophilic substitution

Answer explanation

The reaction between compound C and NaOH is an acid-base reaction, where NaOH acts as a base and neutralizes the acidic component of compound C, resulting in the formation of water and a salt.

What structural feature of compound C can be deduced from its reaction with NaOH?

• Compound C contains an alkyl group

• Compound C contains a carboxyl group (-COOH)

• Compound C contains a hydroxyl group (-OH)

• Compound C contains a carbonyl group (C=O)

Answer explanation

The reaction of compound C with NaOH indicates it contains a carboxyl group (-COOH), as carboxylic acids react with bases to form salts and water, confirming the presence of this functional group.