Organic Chemistry

Meta-nitrobenzoic acid (option 4) is the strongest acid among the given options a nitro group is a strong electron-withdrawing substituent which increases the acidity. When substituted at the meta position, the nitro group stabilizes the negative charge of the conjugate base through inductive effect, making it more stable compared to the options. The decreasing order of acidity is:
• Trichloroacetic acid: phenolic hydroxyl groups (option 1 and 3) weaker
• Formic acid: Strong due to the absence of electron-donating groups.
• Acetic acid: Weaker as the methyl group has an electron-donating effect.
• Benzoic acid: Weakest due to resonance stabilization of the benzene ring.
This shows the relationship between molecular structure and acidity.

Toluene undergoes electrophilic substitution when treated with halogens in the presence of , a Lewis acid catalyst. The methyl group on toluene activates the ortho and para positions for substitution due to its electron-donating effect. The reaction mechanism involves:
Generation of an electrophile
Electrophile attack at the activated positions.
Stabilization of the intermediate carbocation and subsequent restoration of aromaticity.
This reaction is characteristic of aromatic compounds.

Dipole moment measures the separation of positive and negative charges in a molecule. It depends on bond polarity and molecular geometry:
: Significant dipole moment due to one polar C-Cl bond and asymmetric geometry.
: Lower dipole moment as the two C-Cl bonds partially cancel each other.
: Further reduced dipole moment due to three C-Cl bonds.
: No dipole moment due to perfect symmetry.
Thus, has the highest dipole moment due to its single polar bond and lack of significant cancellation.

Nucleophilicity is the ability of a species to donate a lone pair to form a new bond. Factors like charge, electronegativity, and solvent affect nucleophilicity.
• Charge: Anionic species (OH-, NH2-) are stronger nucleophiles than neutral species (H2O, NH3), because of the high electron density resulting from the negative charge.
• Electronegativity: Within the same period, less electronegative atoms are better nucleophiles, for example N is less electronegative than O. NH2- is therefore a better nucleophile than OH-.
Therefore, the order of decreasing nucleophilicity is NH2- >OH->NH3>H2O

Hydrolysis in the presence of an acid breaks specific bonds in molecules to produce different products.
• Phenyl cyanide (benzonitrile) undergoes hydrolysis to form benzoic acid.
• Benzoic anhydride forms two molecules of benzoic acid on acidic hydrolysis.
• Methyl benzoate is an ester that undergoes hydrolysis to form benzoic acid and methanol.
• Benzimidazole will not undergo this type of hydrolysis and will not form benzoic acid.
Thus, the compounds in options A, C and D will form benzoic acid upon acidic hydrolysis.

Vulcanization is a chemical process where rubber is heated with sulfur. This process:
• Forms cross-links between polymer chains of rubber molecules through disulfide bridges between the double bonds present in natural rubber.
• Increases elasticity: These cross-links make the rubber more elastic by reducing the movement of polymer chains.
• Increases hardness: It also makes it harder and more durable as it also increases the tensile strength.
• Reduced solubility It makes it less soluble in solvents.
Therefore, vulcanization makes the rubber more elastic and hard.