Take timed practice tests on Practical Organic Chemistry for JEE Main and JEE Advanced with session-wise drills, score review, and explanation-led revision.
Six 20-question timed sessions plus a 60-question chapter module. Each item is original and reframed for copyright safety.
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1. The Cannizzaro reaction involves:
Explanation: Cannizzaro: aldehydes with no α-H (HCHO, PhCHO) + conc. NaOH → one oxidised (→ carboxylate) + one reduced (→ alcohol). 2HCHO → HCOO⁻ + CH₃OH.
2. To convert aniline to iodobenzene via diazotisation, the reagent used is:
Explanation: Conversion to ArI: ArN₂⁺ + KI → ArI + N₂ + KCl. Unlike Cl and Br (which need CuX catalyst — Sandmeyer), iodide substitution occurs directly with KI (simple heating). Also CuCN for ArCN, HBF₄ for ArF (Balz-Schiemann).
3. The Aldol condensation product of 2 mol acetaldehyde under dilute base is:
Explanation: Aldol reaction: 2CH₃CHO + NaOH(dilute) → CH₃CH(OH)CH₂CHO (3-hydroxybutanal). This is an aldol product. On heating (aldol condensation): −H₂O → CH₃CH=CHCHO (crotonaldehyde/but-2-enal).
4. Wolff-Kishner reduction converts ketones to alkanes using:
Explanation: Wolff-Kishner: ketone → hydrazone (NH₂NH₂) → alkane in strongly basic (KOH) high-T conditions. Compare Clemmensen: Zn(Hg)/conc. HCl (acidic). Both reduce C=O → CH₂. Choose Wolff-Kishner for acid-sensitive substrates.
5. Which reagent converts a primary alcohol to an aldehyde WITHOUT over-oxidising to carboxylic acid?
Explanation: PCC (mild oxidant): 1° ROH → RCHO (stops at aldehyde). KMnO₄, K₂Cr₂O₇/H⁺ (strong oxidants): 1° ROH → RCOOH (full oxidation). 2° ROH → ketone with any oxidant.
6. The sequence to convert benzene to aniline (PhNH₂) is:
Explanation: Benzene → Nitrobenzene (HNO₃/H₂SO₄, 50°C) → Aniline (Fe + HCl, then NaOH; or H₂, Ni catalyst). The nitro group is first introduced then reduced: −NO₂ + 3Fe + 7HCl → −NH₂ + FeCl₃ + 3H₂O (Baeyer's reduction).
7. The Gabriel phthalimide synthesis gives exclusively:
Explanation: Gabriel synthesis: phthalimide K salt + RX → N-alkylphthalimide (SN2) → hydrolysis (acid/base or hydrazine) → RNH₂ (1° amine) + phthalic acid. Because only one N−H is available for substitution, it gives exclusively primary amines.
8. The Fehling's solution test is positive for:
Explanation: Fehling's (Cu²⁺ alkaline tartrate) → reduced to Cu₂O (brick-red) by: (1) reducing sugars (glucose, fructose, maltose), (2) aliphatic aldehydes. NOT by: aromatic aldehydes (PhCHO), ketones, sucrose (non-reducing).
9. Which of these conversions requires a Grignard reagent?
Explanation: Grignard reagents (R'MgX) are the reagent of choice for: (1) adding R' to carbonyl to make alcohols, (2) ester + 2 RMgX → 3° alcohol (RCO then second addition to ketone intermediate). Can also make 1° (with HCHO → 1°), 2° (with RCHO → 2°), 3° (with R₂CO or ester → 3°).