101 Most Wanted Replica: Most Important Organic Chemistry Questions and Answers for NEET by PW

Organic Chemistry can become difficult to revise when questions combine multiple concepts such as IUPAC nomenclature, reaction mechanisms, functional groups, organic conversions, qualitative analysis and biomolecules. You also need to recognise reagents, predict products and apply concepts to unfamiliar reaction sequences.

The PW 101 Most Wanted Replica Organic Chemistry Revision Video For NEET brings 101 important questions and concepts together for focused revision. These notes cover selected questions from the lecture, along with key concepts to revise before practising more NEET-level Organic Chemistry questions.

Most Important Organic Chemistry Questions With Answers

Q1. What is the decreasing order of priority of functional groups in IUPAC naming?

A. Carboxylic acid > ester > cyanide > aldehyde. The highest-priority group becomes the suffix, while the other functional groups are named as prefixes.

Q2. Benzoic acid is treated with soda lime to give X, and X is treated with excess Cl₂/anhydrous AlCl₃. Phenol is treated with Zn to give benzene, and the benzene is treated with excess Cl₂/sunlight to give Y. What is the sum of the degrees of unsaturation of X and Y?

A. The answer is 5.

• Soda-lime decarboxylation of benzoic acid gives benzene. Excess Cl₂/AlCl₃ gives hexachlorobenzene through electrophilic substitution. It has 4 degrees of unsaturation.

• Zn with phenol gives benzene. Excess Cl₂/sunlight gives hexachlorocyclohexane, which has 1 degree of unsaturation because only the ring remains.

• Therefore, 4 + 1 = 5.

Q3. Which test or product does glucose NOT give?

A. Glucose does not give the NaHSO₃ (sodium bisulphite) addition product. It also does not react with Schiff's reagent, according to the lecture. It does react with Tollens' reagent, forms an oxime and forms a cyanohydrin.

Q4. Match maltose, lactose, sucrose and cellulose with their units.

A.

• Maltose = two α-D-glucose units.

• Lactose = β-D-galactose + β-D-glucose.

• Sucrose = α-D-glucose + β-D-fructose.

• Cellulose = polymer of β-D-glucose.

Q5. A mixture of formaldehyde and acetaldehyde is heated with dilute NaOH. What is the IUPAC name of the major product?

A. Prop-2-en-1-al (acrolein, CH₂=CH–CHO). Formaldehyde has no α-hydrogen and acts as the electrophile, while acetaldehyde supplies the α-hydrogen. On heating, the aldol product loses water to form the α,β-unsaturated aldehyde.

Q6. Toluene is treated with KMnO₄, then SOCl₂, then H₂/Pd–BaSO₄. What is the final product?

A. Benzaldehyde (C₆H₅CHO).

• KMnO₄ oxidises toluene to benzoic acid.

• SOCl₂ converts benzoic acid into benzoyl chloride.

• H₂/Pd–BaSO₄ carries out Rosenmund reduction to give benzaldehyde.

Q7. 0.4 g of an organic compound was analysed by Kjeldahl's method. The ammonia evolved neutralised 25 mL of 0.2 M H₂SO₄. What is the percentage of nitrogen?

A. Using the formula % N = (1.4 × N × V) / w:

• Normality = 0.2 × 2 = 0.4 N

• V = 25 mL

• w = 0.4 g

• % N = (1.4 × 0.4 × 25) / 0.4

• % N = 35%

Q8. How can you distinguish between (a) propanal and propanone, (b) ethanol and tert-butyl alcohol, (c) phenol and benzoic acid, and (d) ethylamine and diethylamine?

A.

• (a) Tollens' reagent: Propanal gives a silver mirror, while propanone does not.

• (b) Lucas reagent: Tert-butyl alcohol gives immediate turbidity, while ethanol reacts much more slowly.

• (c) NaHCO₃: Benzoic acid gives CO₂ effervescence, while phenol does not.

• (d) Carbylamine test: Ethylamine, a primary amine, gives the isocyanide test, while diethylamine, a secondary amine, does not.

Q9. Which statement about enzymes is incorrect?

A. The incorrect statement is “Enzymes work by increasing the activation energy of the reaction.” Enzymes lower activation energy and increase the rate of reaction.

Q10. Benzene is nitrated, reduced to aniline, diazotised and treated with CuCl/HCl to give chlorobenzene. A second chlorination with Cl₂/FeCl₃ gives ortho and para products. What is the best way to separate them?

A. Crystallisation or fractional crystallisation. The para isomer is more symmetrical and generally packs more efficiently in the crystal, giving it a higher melting point.

Q11. Which statement about the bromination of phenol is incorrect?

A. The incorrect statement is “Phenol needs FeBr₃ as a catalyst for bromination.” The –OH group strongly activates the benzene ring, so phenol undergoes bromination without requiring FeBr₃.

• Phenol + bromine water gives 2,4,6-tribromophenol.

• Phenol with Br₂ in a non-aqueous solvent gives ortho- and para-bromophenol.

• The –OH group activates the ring towards electrophilic substitution.

Q12. How many sigma and pi bonds are present in but-1-en-3-yne?

A. The structure is CH₂=CH–C≡CH.

• Sigma bonds = 3 C–C + 4 C–H = 7

• Pi bonds = 1 from the double bond + 2 from the triple bond = 3

Therefore, the compound contains 7 sigma bonds and 3 pi bonds.

Q13. Compound P reacts with sodium to release H₂ but gives no colour with neutral FeCl₃. On oxidation with acidified K₂Cr₂O₇ it gives Q, which effervesces with NaHCO₃. What are P and Q?

A. P is benzyl alcohol and Q is benzoic acid.

• Reaction with sodium indicates the presence of an –OH group.

• No colour with neutral FeCl₃ rules out a phenolic –OH.

• Oxidation of benzyl alcohol gives benzoic acid.

• Benzoic acid reacts with NaHCO₃ with CO₂ effervescence.

Q14. Match vitamins A, B12, C, D, E and K with their deficiency diseases or effects.

A.

• Vitamin A: Xerophthalmia and night blindness.

• Vitamin B12: Pernicious anaemia.

• Vitamin K: Blood clotting.

• Vitamin C: Scurvy.

• Vitamins D and E should be revised along with their corresponding deficiency effects.

Q15. An organic compound gives a Prussian blue colour in Lassaigne's test but no blood-red colour. Which element does it contain?

A. Nitrogen only. Prussian blue indicates the formation of a ferrocyanide complex in the presence of nitrogen. The blood-red colour associated with thiocyanate requires sulphur along with nitrogen. Therefore, in this case, nitrogen is present while sulphur is absent.

Q16. Identify the correct statements about nucleic acids.

A.

• The statement that DNA contains β-D-ribose is incorrect. DNA contains β-D-2-deoxyribose.

• RNA contains uracil, while DNA contains thymine.

• A nucleoside consists of a nitrogenous base and pentose sugar. Addition of phosphate gives a nucleotide.

• In double-stranded DNA, guanine pairs with cytosine through three hydrogen bonds.

• The two DNA strands are complementary and antiparallel, not parallel with identical sequences.

Q17. Match the reactions of phenol with their products.

A.

• Phenol + CHCl₃/NaOH, followed by HCl → salicylaldehyde through the Reimer-Tiemann reaction.

• Phenol + CO₂/NaOH, followed by HCl → salicylic acid through the Kolbe-Schmidt reaction.

• Phenol + concentrated HNO₃ → picric acid (2,4,6-trinitrophenol).

Q18. Can ketones be prepared from nitriles using a Grignard reagent?

A. Yes. A Grignard reagent attacks the electrophilic carbon of the nitrile to form an imine-magnesium salt. Hydrolysis of this intermediate gives a ketone.

Q19. Which compound will NOT undergo the Hell-Volhard-Zelinsky reaction?

A. A carboxylic acid having no α-hydrogen will not undergo the HVZ reaction. The reaction requires at least one α-hydrogen for halogenation at the α-carbon.

Q20. Match each mixture with the appropriate purification technique.

A.

• Essential oils from plant material → Steam distillation

• Acetone + methyl alcohol with a small boiling-point difference → Fractional distillation

• Glycerol from spent soap lye → Distillation under reduced pressure

• Mixtures with a larger boiling-point difference → Simple distillation

Q21. What is the total number of stereoisomers of 2-chloro-3-methylbutane?

A. 2 stereoisomers. The structure is CH₃–CHCl–CH(CH₃)–CH₃. Only C-2 is chiral because C-3 has two identical methyl groups. Therefore, there is one pair of enantiomers.

Q22. What is the decreasing order of basic strength of methylamines in aqueous solution?

A. (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃

Thus, the order is 2° amine > 1° amine > 3° amine > ammonia. In aqueous solution, the +I effect, steric effects and solvation all influence basic strength.

Q23. What are the products when an aryl methyl ether such as anisole is heated with HI?

A. Phenol + methyl iodide (CH₃I). Cleavage occurs at the O–CH₃ bond rather than the aryl–O bond because the aryl–O bond has partial double-bond character due to resonance.

Q24. Compound P (C₃H₆O) reduces Tollens' reagent. With dilute NaOH and heat it undergoes condensation to give Q. Identify P and Q.

A. P is propanal (CH₃CH₂CHO), and Q is 2-methylpent-2-enal.

• C₃H₆O and a positive Tollens' test indicate an aldehyde, giving propanal.

• Propanal undergoes self-aldol condensation in the presence of dilute NaOH.

• On heating, the aldol product loses water to form 2-methylpent-2-enal.

Most Important Organic Chemistry Topics to Revise

The official NEET Chemistry syllabus includes core areas such as basic principles of Organic Chemistry, hydrocarbons, compounds containing halogens, oxygen and nitrogen, biomolecules and related organic concepts. The table below groups the major areas that should be revised along with the concepts tested in the lecture.

Organic Chemistry revision becomes easier when you connect reactions, mechanisms, functional groups, named reactions and important conversions instead of revising them in isolation. The PW 101 Most Wanted Replica Organic Chemistry Revision Video brings important questions together for quick revision and practice.

Revise important Organic Chemistry concepts and practise 101 most-wanted questions with answers in this PW revision video. 

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