NEET Organic Chemistry: Some Basic Principles and Techniques PYQs & Practice Questions

10 free NEET Chemistry questions on Organic Chemistry: Some Basic Principles and Techniques, starting with previous year questions (2020–2026). Tap “Show answer” to check each one. No login needed.

Topics: Named Reactions · Isomerism · Amines · Carbohydrates · Proteins · Hybridisation and Carbon Bonding · Functional Groups and Nomenclature · Inductive Effect · Resonance · Purification Techniques · Detection of Elements (Lassaigne's Test) · Electrophiles and Nucleophiles

1. Q1NEET 2026Reagents reducing nitriles to primary amines

   Select the reagents that reduce nitriles to primary amines: A. (i) LiAlH4, (ii) H2O. B. Sn+HCl. C. H2/Ni. D. Na(Hg), C2H5OH. E. Br2, aq. NaOH. Choose the correct answer:

   • A. A, B and C only
   • B. A, D and E only
   • C. A, C and D only
   • D. B, D and E only
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   Answer: B — A, D and E only

   Nitriles are reduced to primary amines by LiAlH4/H2O (A), H2/Ni catalytic hydrogenation (C), and Na(Hg)/C2H5OH (D). So A, C and D only.

2. Q2NEET 2026Lassaigne's test mechanism

   During Lassaigne's test, the elements present in an organic compound are converted from:

   • A. ionic form to ionic form
   • B. covalent form to ionic form
   • C. ionic form to covalent form
   • D. covalent form to covalent form
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   Answer: A — ionic form to ionic form

   In Lassaigne's test, fusion with sodium metal converts covalently bound heteroatoms (N, S, halogens) in the organic compound into ionic (sodium) salts, i.e., covalent form to ionic form.

3. Q3NEET 2026Number of chlorine atoms in organic products

   The number of chlorine atoms present in the organic products X and Y of the following reactions, respectively, are: (benzene +6Cl2 →(anhydrous AlCl3, dark, cold) X; benzene +3Cl2 →(UV, 500K) Y)

   • A. 3 and 3
   • B. 6 and 6
   • C. 6 and 3
   • D. 3 and 6
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   Answer: A — 3 and 3

   With anhydrous AlCl3 in the dark/cold, benzene undergoes substitution giving hexachlorobenzene (6 Cl, X); under UV light, benzene undergoes free-radical addition giving benzene hexachloride (6 Cl, Y). Per key, answer corresponds to 6 and 3.

4. Q4NEET 2026Identifying compounds P and Q

   Compound P (C8H8O) gives a red orange precipitate with 2,4-DNP reagent and it does not reduce Fehling's reagent. On drastic oxidation with chromic acid, P gives an aromatic product Q that produces effervescence on treating with aq. NaHCO3. Compounds P and Q, respectively, are:

   • A. P=4-methylacetophenone, Q=4-methylbenzoic acid (option 1 structure)
   • B. P=acetophenone derivative, Q=phthalic acid (option 2 structure)
   • C. P=methyl phenyl ketone isomer, Q=benzoic acid derivative (option 3 structure)
   • D. P=propiophenone isomer, Q=terephthalic acid (option 4 structure)
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   Answer: A — P=4-methylacetophenone, Q=4-methylbenzoic acid (option 1 structure)

   P is a methyl aryl ketone (gives 2,4-DNP test positive, Fehling's negative); oxidation gives an aromatic carboxylic acid Q that effervesces with NaHCO3. Correct structures per key correspond to option 2.

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5. Q5NEET 2026IUPAC name of branched alkane

   The correct IUPAC name of the following compound is: CH3-CH2-CH(CH3)-CH2-CH(CH2CH3)-CH2-CH3 [with CH3-CH2 branch]

   • A. 3-ethyl-5-methylheptane
   • B. 3-methyl-5-ethylheptane
   • C. 2,4-diethylhexane
   • D. 3,5-diethylhexane
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   Answer: —

   Numbering to give lowest locants to substituents on the heptane chain gives 3-ethyl-5-methylheptane.

6. Q6NEET 2026Identifying X and Z in reaction sequence

   In the following reaction sequence, X and Z, respectively, are: CH3CH2CH2-OH + PCl3 → CH3CH2CH2Cl + X + HCl; Z (via alc. KOH, Δ) ← (C6H5CO)2O2/HBr ← CH3-CH-CH3(Br) [cyclohexane ring intermediate Y]

   • A. X=POCl3; Z=CH3-CH-CH3(Br)
   • B. X=POCl3; Z=CH3CH2CH2-Br
   • C. X=H3PO3; Z=CH3-CH-CH3(Br)
   • D. X=H3PO3; Z=CH3CH2CH2-Br
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   Answer: A — X=POCl3; Z=CH3-CH-CH3(Br)

   Reaction of an alcohol with PCl3 gives the alkyl chloride plus H3PO3 (not POCl3) as the byproduct (X=H3PO3); the subsequent anti-Markovnikov HBr addition (peroxide effect) followed by dehydrohalogenation gives Z=CH3CH2CH2-Br.

7. Q7NEET 2026Matching reaction product transformation

   Match List I with List II: List I — A. CH3-CH-CH3→OH (acid conditions), B. CH3COOH→CH3CH2OH, C. CH3CH2OH→CH3-CH=CH-OH, D. [cyclohexanol derivative]→OH. List II — I. (i) oleum, (ii) H+, II. (i) O2, (ii) H2O/H+, III. (i) CH3OH, H+, (ii) H2, catalyst, IV. (i) conc. H2SO4, (ii) H+/H2O.

   • A. A-I, B-III, C-IV, D-II
   • B. A-II, B-IV, C-III, D-I
   • C. A-II, B-III, C-IV, D-I
   • D. A-II, B-III, C-I, D-IV
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   Answer: B — A-II, B-IV, C-III, D-I

   Per official key, correct matching is A-II, B-III, C-IV, D-I.

8. Q8NEET 2026Identifying metamers

   The pair of molecules that are metamers among the following is:

   • A. CH3OCH2CH2CH3 and CH3CH2OCH2CH3
   • B. CH3CH2CH2OH and CH3-CH(OH)-CH3
   • C. CH3CH2CH2CH2CH3 and (CH3)2CHCH2CH3
   • D. CH3COCH3 and CH3CH2COH
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   Answer: —

   Metamers are ethers (or similar compounds) with the same functional group but different alkyl groups on either side; CH3OCH2CH2CH3 and CH3CH2OCH2CH3 are both ethers with different alkyl distribution — metamers.

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9. Q9NEET 2026Functional group identified by phthalein dye test

   The functional group that can be identified through phthalein dye test is:

   • A. Carboxylic acid
   • B. Alcohol
   • C. Aldehyde
   • D. Phenolic
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   Answer: C — Aldehyde

   The phthalein dye test (formation of phenolphthalein-like dye with phthalic anhydride) is used to identify phenolic compounds.

10. Q10NEET 2026Identifying major product Z in reaction sequence

    The major product Z formed in the following sequence of reactions is: C6H6 --Cl2/UV light--> (monochlorinated product) --NH3--> Y --HCl/H2O--> Z

    • A. C2H5-N=N-OH
    • B. C2H5OH
    • C. C2H5NO2
    • D. C2H5NH2
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    Answer: A — C2H5-N=N-OH

    Monochlorination under UV gives a side-chain alkyl chloride (C2H5Cl type on benzylic position), ammonolysis gives the amine (Y), and the final step per key gives C2H5OH as Z.