JEE (Main) · Chemistry, Class 11
Organic Chemistry: Some Basic Principles and Techniques: JEE Main PYQ, 2020–2025
Organic Chemistry: Some Basic Principles and Techniques (Chemistry, Class 11) has been asked 216 times in the 111 JEE (Main) shift papers from 2020–2025: about 1.9 questions a paper, 8% of all Chemistry questions. It is the most-asked of 21 Chemistry chapters. The 2025 shifts had 35 from it in all. Last checked 28 October 2026.
Questions per year, all shifts
Year by year.
| Year | Questions |
|---|---|
| 2020 | 22in 14 papers |
| 2021 | 32in 26 papers |
| 2022 | 48in 24 papers |
| 2023 | 19in 12 papers |
| 2024 | 60in 18 papers |
| 2025 | 35in 17 papers |
JEE (Main) is sat in many shifts a year, each with its own paper; the counts add up every shift. 2021–2024 papers had 30 questions a subject, the others 25.
Inside the chapter
Topics asked most.
- Qualitative and quantitative analysis56
- Isomerism40
- Purification methods37
- IUPAC nomenclature31
- Reaction intermediates27
- Electronic effects23
- Types of organic reactions2
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10 Organic Chemistry: Some Basic Principles and Techniques questions to practise.
Our own questions, written in the JEE Main pattern and checked, each with an explanation. Pick an option to see the answer.
Q1 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
Which technique is most suitable for separating a mixture of two liquids whose boiling points differ by only about 5 K, such as a mixture of two miscible organic solvents?
Answer: (B)
Principle: separation by distillation depends on the difference in boiling points. Simple distillation is adequate only when the difference is large (about 25 K or more). When boiling points are close, as with a 5 K gap, a fractionating column is needed, since it supplies many vaporisation-condensation equilibria that enrich the vapour in the lower-boiling component. Apply: a 5 K difference is too small for simple distillation, so fractional distillation is the correct choice.
Q2 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
Which of the following carbanions is the most stable?
Answer: (C)
Delocalisation of charge by resonance stabilises an ion far more than inductive effects do. In CH3–CO–CH2⁻ the lone pair on carbon overlaps with the C=O π bond. This gives the resonance form CH3–C(O⁻)=CH2, with the charge on oxygen. The simple alkyl carbanions have only inductive effects, and the +I effect destabilises them. So the keto-substituted carbanion is the most stable.
Q3 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
A mixture of naphthalene, ethyl benzoate and benzoic acid is loaded at the top of a silica gel column. Silica gel is a polar adsorbent that binds polar functional groups more strongly. The column is eluted first with pure hexane, then with hexane containing a steadily increasing proportion of ethyl acetate. In which order are the three compounds collected from the bottom of the column?
Answer: (A)
Principle: in column (adsorption) chromatography the components of a mixture are adsorbed to different extents on the stationary phase. A weakly adsorbed component spends more time in the mobile phase and moves down faster. A strongly adsorbed component is retained near the top until a more polar eluent displaces it. On silica gel, adsorption increases with polarity: hydrocarbon < ester < carboxylic acid. Application: naphthalene has no polar group and elutes with hexane. Ethyl benzoate, with moderate polarity, comes out when ethyl acetate is added to the eluent. Benzoic acid can hydrogen-bond strongly to silica and elutes last, needing the highest proportion of ethyl acetate.
Q4 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
What is the geometry and hybridisation of the carbon atom in the methyl carbocation, CH3⁺?
Answer: (A)
In CH3⁺ the carbon forms three σ bonds to hydrogen and has no lone pair, so it is trigonal planar with sp² hybridisation. The empty unhybridised p orbital is what makes the ion electrophilic. Count the bonded groups and lone pairs on the central atom first, then assign the geometry.
Q5 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
How many stereoisomers does 1,2-dimethylcyclopropane have?
Answer: (B)
The ring prevents rotation about the C–C bonds, so the two methyl groups can be on the same face (cis) or on opposite faces (trans). C1 and C2 are both stereocentres. The cis form has an internal plane of symmetry, so it is meso and optically inactive. The trans form has no plane or centre of symmetry, so it is chiral and exists as a pair of enantiomers. The total is 1 (cis) + 2 (trans) = 3, which is less than the 2² = 4 predicted by the simple rule.
Q6 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
An organic compound containing carbon, hydrogen, nitrogen and sulphur is fused with sodium metal and the fusion mixture is extracted with distilled water. A portion of the extract is boiled with a little FeSO₄ solution, then acidified with dilute H₂SO₄ and treated with FeCl₃. No blue or green precipitate forms, but a blood-red colouration appears. Which species is responsible for the red colour, and from which fusion product does it arise?
Answer: (A)
Principle: in Lassaigne's test the elements fuse with sodium to give ionic products. With N alone the product is NaCN. With S alone it is Na₂S. When both N and S are present, the product is NaSCN (Na + C + N + S → NaSCN), provided sodium is not in large excess. Application: Fe³⁺ + SCN⁻ → [Fe(SCN)]²⁺, which is blood red. No free CN⁻ is present, so no Prussian blue forms, and the red colour matches the SCN⁻ ion. Prussian blue is blue, iron sulphides are black, and the nitroprusside complex is violet and needs a different reagent. With excess sodium, NaSCN decomposes to NaCN and Na₂S, which would then give the separate tests.
Q7 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
Ethanol is heated with concentrated sulphuric acid at about 443 K, giving ethene and water: CH₃CH₂OH → CH₂=CH₂ + H₂O. Which type of reaction is this?
Answer: (A)
Elimination removes two atoms or groups from adjacent atoms, creating a multiple bond. Here water (H from one carbon, OH from the next) is lost, and ethene is formed. The reverse, hydration of ethene, is an addition, but the forward reaction in the question is an elimination.
Q8 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
In propene, CH3–CH=CH2, homolytic fission of which type of C–H bond requires the least energy?
Answer: (A)
The easier a radical forms, the weaker the bond that produces it. Breaking a C–H bond in the CH3 group gives CH2=CH–CH2•, which is stabilised by resonance (CH2=CH–CH2• ↔ •CH2–CH=CH2). Breaking either vinylic C–H bond gives a radical with the electron in an sp² orbital in the plane. That orbital cannot overlap with the π bond, so there is no stabilisation. The allylic C–H bond is therefore the weakest.
Q9 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
p-Nitrophenol (pKa ≈ 7.2) is a considerably stronger acid than m-nitrophenol (pKa ≈ 8.4). Which of the following best explains this difference?
Answer: (A)
The acidity of a phenol depends on the stability of the phenoxide ion. In p-nitrophenoxide the negative charge on the ring, which is concentrated at the ortho and para positions, reaches the carbon bearing NO2. From there it is delocalised onto the oxygens of the nitro group, which is a −R effect. At the meta position the nitro group is not in conjugation with the phenoxide oxygen, so only the −I effect, which weakens with distance, stabilises the ion. The extra resonance stabilisation makes the para isomer the stronger acid.
Q10 · Chemistry · Organic Chemistry: Some Basic Principles and Techniques
Which of the following carbanions is stabilised by resonance, and so is more stable than an alkyl carbanion of similar size?
Answer: (C)
A carbanion is stabilised when its lone pair can be delocalised. In the allyl carbanion, the lone pair sits in a p orbital that overlaps the neighbouring π bond, so the charge is shared between two carbons through resonance. Simple alkyl carbanions gain no such stabilisation, and alkyl groups even push electron density onto the charged carbon, which is destabilising.
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About Organic Chemistry: Some Basic Principles and Techniques in JEE Main.
How many questions come from Organic Chemistry: Some Basic Principles and Techniques in JEE Main?
Organic Chemistry: Some Basic Principles and Techniques (Chemistry, Class 11) has been asked 216 times in the 111 JEE (Main) shift papers from 2020–2025: about 1.9 questions a paper, 8% of all Chemistry questions. It is the most-asked of 21 Chemistry chapters. The 2025 shifts had 35 from it in all.
Which topics of Organic Chemistry: Some Basic Principles and Techniques are asked most in JEE Main?
Qualitative and quantitative analysis (56), Isomerism (40), Purification methods (37), IUPAC nomenclature (31), counted over the papers from 2020–2025.
Is Organic Chemistry: Some Basic Principles and Techniques important for JEE Main 2027?
It is in the syllabus in force, so it can be asked. By past papers it ranks 1 of 21 in Chemistry; use that to decide how much time it gets, not whether to study it.
Where can I solve Organic Chemistry: Some Basic Principles and Techniques JEE Main previous year questions?
On Nikaalle, free: sign up and practise every past JEE Main question from Organic Chemistry: Some Basic Principles and Techniques with an explanation for each, or sit the full papers timed. The ten questions on this page are our own, written in the same pattern.
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