General Organic Chemistry

14 NEET-UG practice questions on General Organic Chemistry, part of Chemistry. The first 14 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   Assertion A: Chloroethanoic acid is a stronger acid than ethanoic acid. Reason R: The –I effect of chlorine disperses the negative charge of the carboxylate ion and stabilises it. Choose the correct answer.

   1. AA is correct but R is not correct
   2. BA is not correct but R is correct
   3. CBoth A and R are correct but R is not the correct explanation of A
   4. DBoth A and R are correct and R is the correct explanation of A

   Show answerHide answer

   Answer: D · Both A and R are correct and R is the correct explanation of A

   Chlorine withdraws electron density through the σ bonds, so the conjugate base is more stable than ethanoate. A more stable conjugate base means a stronger acid, so R explains A directly.

   • A: R is correct; chlorine has a –I effect that stabilises the anion.
   • B: A is correct; chloroethanoic acid is the stronger acid.
   • C: R is the actual cause of the higher acidity, not an unrelated fact.

   Remember this

   An electron-withdrawing group raises acid strength by stabilising the conjugate base; the effect falls with distance.

2. Question 2 · Medium

   In a Kjeldahl estimation, the ammonia obtained from 0.70 g of an organic compound exactly neutralised 10 mL of 0.5 M H₂SO₄. Calculate the percentage of nitrogen in the compound. (Take N = 14.)

   1. A10%
   2. B24.3%
   3. C20%
   4. D40%

   Show answerHide answer

   Answer: C · 20%

   H₂SO₄ used = 10 × 0.5 = 5 mmol. Since 2NH₃ + H₂SO₄ → (NH₄)₂SO₄, NH₃ = 10 mmol, so N = 10 mmol × 14 = 0.14 g. Percentage = (0.14/0.70) × 100 = 20%.

   • A: Takes one mole of NH₃ per mole of H₂SO₄, missing the factor of 2.
   • B: Uses the mass of NH₃ (17) in place of the mass of N (14).
   • D: Applies the factor of 2 twice.

   Remember this

   One mole of H₂SO₄ neutralises two moles of NH₃, and each NH₃ carries one nitrogen atom.

3. Question 3 · Medium

   Arrange these alkyl cations from the least stable to the most stable, judging by their α-hydrogens. A. CH₃CH₂⁺ B. (CH₃)₃C⁺ C. CH₃⁺ D. (CH₃)₂CH⁺

   1. AB, D, A, C
   2. BC, A, D, B
   3. CA, C, D, B
   4. DC, D, A, B

   Show answerHide answer

   Answer: B · C, A, D, B

   The α-C–H counts are CH₃⁺ 0, CH₃CH₂⁺ 3, (CH₃)₂CH⁺ 6 and (CH₃)₃C⁺ 9. More α-C–H bonds mean more hyperconjugation and more +I release, so stability rises in that order.

   • A: Gives the decreasing order, the reverse of what is asked.
   • C: Places the methyl cation above the ethyl cation, which has hyperconjugation.
   • D: Places the 2° cation below the 1° cation.

   Remember this

   Among simple alkyl carbocations, stability follows 3° > 2° > 1° > methyl, tracking the number of α-hydrogens.

4. Question 4 · Hard

   Arrange the following benzylic carbocations in increasing order of stability. A. p-Methylbenzyl cation B. p-Nitrobenzyl cation C. p-Methoxybenzyl cation D. Benzyl cation

   1. AB, A, D, C
   2. BC, A, D, B
   3. CB, D, A, C
   4. DD, B, A, C

   Show answerHide answer

   Answer: C · B, D, A, C

   A para substituent can stabilise or destabilise the positive charge delocalised on to the ring. –NO₂ (–I, –R) destabilises it, –CH₃ helps by hyperconjugation and +I, and –OCH₃ helps most through its lone pair (+R).

   • A: Places p-methylbenzyl below benzyl, ignoring the electron release from methyl.
   • B: Gives the decreasing order, the reverse of what is asked.
   • D: Places the unsubstituted cation below the destabilised nitro cation.

   Remember this

   A para group donating by +R stabilises a benzylic cation far more than hyperconjugation; a –R group destabilises it.

5. Question 5 · Medium

   Glycerol decomposes at or below its normal boiling point. The technique used to recover it from spent lye in the soap industry is

   1. Adistillation under reduced pressure
   2. Bsimple distillation at atmospheric pressure
   3. Csublimation
   4. Dcrystallisation from water

   Show answerHide answer

   Answer: A · distillation under reduced pressure

   Lowering the external pressure makes a liquid boil at a lower temperature, so glycerol distils before it can decompose.

   • B: At atmospheric pressure glycerol would decompose before distilling.
   • C: Sublimation applies to solids that pass directly into vapour.
   • D: Crystallisation purifies solids, and glycerol is a liquid.

   Remember this

   Reduced pressure distillation suits liquids with very high boiling points and those that decompose at or below their boiling point.

6. Question 6 · Medium

   How many structural isomers of molecular formula C₄H₁₀O contain the ether functional group?

   1. A3
   2. B7
   3. C4
   4. D2

   Answer and explanation in LearnFree account

7. Question 7 · Medium

   Given below are two statements: Statement I: The tert-butyl cation is more stable than the ethyl cation. Statement II: Hyperconjugation involves delocalisation of the σ electrons of a C–H bond of an alkyl group attached to an atom with an unshared p orbital. Choose the correct answer.

   1. ABoth Statement I and Statement II are correct
   2. BStatement I is incorrect but Statement II is correct
   3. CBoth Statement I and Statement II are incorrect
   4. DStatement I is correct but Statement II is incorrect

   Answer and explanation in LearnFree account

8. Question 8 · Easy

   On a thin layer chromatography plate, a spot travelled 2.4 cm while the solvent front travelled 6.0 cm from the same base line. What is the retardation factor of the compound?

   1. A2.5
   2. B0.60
   3. C0.40
   4. D3.6

   Answer and explanation in LearnFree account

9. Question 9 · Easy

   What is the IUPAC name of CH₃–CH=CH–CH(CH₃)–CHO?

   1. A2-Methylpent-2-enal
   2. B4-Methylpent-2-enal
   3. C2-Methylpent-3-enal
   4. D3-Methylpent-3-enal

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    Match List-I with List-II. List-I (element tested in the sodium fusion extract) A. Nitrogen B. Sulphur C. Chlorine D. Nitrogen and sulphur together List-II (observation in the test) I. Blood red colour with Fe³⁺ II. White precipitate with AgNO₃, soluble in ammonia III. Prussian blue colour IV. Violet colour with sodium nitroprusside

    1. AA-III, B-IV, C-II, D-I
    2. BA-I, B-IV, C-III, D-II
    3. CA-IV, B-III, C-II, D-I
    4. DA-III, B-I, C-II, D-IV

    Answer and explanation in LearnFree account

11. Question 11 · Hard

    Consider the following statements about electronic effects. A. The –NO₂ group shows both –I and –R effects. B. The –OCH₃ group shows a –I effect and a +R effect. C. In –Cl attached to a benzene ring, the –I effect outweighs the +R effect. D. Hyperconjugation is possible in CH₃⁺ because it has three C–H bonds. Which of these statements are correct?

    1. AA, B, C and D
    2. BB and D only
    3. CA and C only
    4. DA, B and C only

    Answer and explanation in LearnFree account

12. Question 12 · Easy

    Give the IUPAC name of the compound drawn.

    

    EnlargeClose

    

    1. A4-Methylhexan-2-ol
    2. B1,3-Dimethylbutan-1-ol
    3. C4-Methylpentan-2-ol
    4. D2-Methylpentan-4-ol

    Answer and explanation in LearnFree account

13. Question 13 · Hard

    Propenal is CH₂=CH–CHO. Which structure in the figure is NOT a resonance contributor of propenal?

    

    EnlargeClose

    

    1. AStructure C
    2. BStructure B
    3. CStructure D
    4. DStructure A

    Answer and explanation in LearnFree account

14. Question 14 · Medium

    Arrange the carbocations drawn in the figure in order of increasing stability. A. Structure A B. Structure B C. Structure C D. Structure D

    

    EnlargeClose

    

    1. AA, C, D, B
    2. BA, C, B, D
    3. CA, B, C, D
    4. DC, A, B, D

    Answer and explanation in LearnFree account