Chemistry - Nomenclature Question with Solution | TestHub

Question Explanation:

This matching question requires classification of compounds based on ring type , σ / π bond count (odd/even) , and degree of unsaturation (DU) .

Concepts:

Involved Homocyclic vs Heterocyclic compounds

Hydrocarbon vs heteroatom-containing compounds

Counting σ and π bonds

Degree of Unsaturation (DU)

Solution

(I) Pyridine (C₅H₅N)

Contains N in the ring → Heterocyclic (R)

σ-bonds = 11 → Odd (T)

π-bonds = 3

DU = 1 (ring) + 3 (π bonds) = 4 → DU ≥ 4 (U)

Match: R, T, U

(II) Cyclopentadiene (C₅H₆ )

Carbocyclic ring → Homocyclic (P)

Contains only C and H → Hydrocarbon (Q)

π-bonds = 2 → Even (S)

σ-bonds = 11 → Odd (T)

DU = 1 + 2 = 3

Match: P, Q, S, T 6 5

(III) Phenylhydroxylamine (C₆H₅NHOH)

Benzene ring → Homocyclic (P)

σ-bonds = 15 → Odd (T)

π-bonds = 3

DU = 1 + 3 = 4 → DU ≥ 4 (U)

Match: P, T, U

(IV) Naphthalene (C₁₀H₈ )

Fused carbocyclic rings → Homocyclic (P)

Contains only C and H → Hydrocarbon (Q)

σ-bonds = 19 → Odd (T)

π-bonds = 5

DU = 2 + 5 = 7 → DU ≥ 4 (U)

Match: P, Q, T, U

Final Answer: Option (C)