Organic Chemistry — Some Basic Principles

Easy Recall (3)Direct Application (3)Concept Trap (2)

Electromeric Effect

Easy Recall (3)Direct Application (3)Concept Trap (2)

Electrophiles Nucleophiles

Easy Recall (3)Direct Application (3)Concept Trap (2)

Free Radicals Carbocations

8 MCQs1 revision cardWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Hybridization Organic

8 MCQs1 PYQsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Hyperconjugation

8 MCQs3 PYQs2 revision cardsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Inductive Effect

Easy Recall (3)Direct Application (3)Concept Trap (2)

IUPAC Nomenclature Organic

8 MCQs2 PYQsWorked example

Direct Application (3)Easy Recall (3)Calculation (2)

Resonance Organic

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Structural Stereoisomerism

8 MCQs6 PYQsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Tetravalency Carbon

Easy Recall (3)Direct Application (3)Concept Trap (1)Calculation (1)

Past-paper questions from this unit

12 questions from NEET 2020, 2021, 2022, 2023, 2024, 2025, 2026. Answers verified against NTA official keys.

By year in our set: 2020 (1) · 2021 (1) · 2022 (2) · 2023 (1) · 2024 (1) · 2025 (3) · 2026 (3)

Lesson: Hyperconjugation

NEET 2026

The following carbocation (C₆H₅–CH⁺–CH₃, the 1-phenylethyl cation) is stabilized by the interaction of the empty p orbital with

1filled σ and filled π orbitals

2empty σ and empty π* orbitals

3empty σ* and filled π orbitals

4empty σ* and empty π* orbitals

NTA Answer: Option 1(final)

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Given below are two statements, with the products shown in the figure: Statement-I : trans-But-2-ene upon treatment with Br₂ in CCl₄ gives the product drawn on the left. Statement-II : cis-But-2-ene upon treatment with alkaline KMnO₄ gives the product drawn on the right. In the light of the above statements, choose the most appropriate answer from the options given below.

NEET 2026

1Both Statement I and Statement II are correct

2Both Statement I and Statement II are incorrect

3Statement-I is correct, but Statement-II is incorrect

4Statement-I is incorrect, but Statement-II is correct

NTA Answer: Option 4(final)

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Consider the following reaction sequences and choose the correct option. Ph–C≡C–Me with Na/liq. NH₃ gives L; Ph–C≡C–Me with H₂/Pd-C (Lindlar's catalyst) gives K; L with HBr and benzoyl peroxide gives N; K with HBr gives M.

NEET 2026

1K and L are geometrical isomers

2K and L are enantiomers

3M and N are geometrical isomers

4M and N are stereoisomers

NTA Answer: Option 1(final)

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Which one of the following compounds can exist as cis-trans isomers?

NEET 2025

11, 2-Dimethylcyclohexane

2Pent-1-ene

32-Methylhex-2-ene

41, 1-Dimethylcyclopropane

NTA Answer: Option 1(final)

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Lesson: Hyperconjugation

NEET 2025

Among the given compounds I-III, the correct order of bond dissociation energy of C–H bond marked with * is :

1II > III > I

2II > I > III

3I > II > III

4III > II > I

NTA Answer: Option 2(final)

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Total number of possible isomers (both structural as well as stereoisomers) of cyclic ethers of molecular formula C4H8O is :

NEET 2025

111

410

NTA Answer: Option 4(final)

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A compound with a molecular formula of C₆H₁₄ has two tertiary carbons. Its IUPAC name is :

NEET 2024Revised key

1n-hexane

22-methylpentane

32,3-dimethylbutane

42,2-dimethylbutane

NTA Answer: Option 3(revised_final)

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Lesson: Hybridization Organic

NEET 2023

The number of σ bonds, π bonds and lone pair of electrons in pyridine, respectively are:

112, 3, 0

211, 3, 1

312, 2, 1

411, 2, 0

NTA Answer: Option 2(final)

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The incorrect statement regarding chirality is

NEET 2022

1A racemic mixture shows zero optical rotation

2SN1 reaction yields 1 : 1 mixture of both enantiomers

3The product obtained by SN2 reaction of haloalkane having chirality at the reactive site shows inversion of configuration

4Enantiomers are superimposable mirror images on each other

NTA Answer: Option 4(final)

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The correct IUPAC name of the following compound is

NEET 2022

16-bromo-4-methyl-2-chlorohexan-4-ol

21-bromo-5-chloro-4-methylhexan-3-ol

36-bromo-2-chloro-4-methylhexan-4-ol

41-bromo-4-methyl-5-chlorohexan-3-ol

NTA Answer: Option 2(final)

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The compound which shows metamerism is :

NEET 2021

1C₄H₁₀O

2C₅H₁₂

3C₃H₈O

4C₃H₆O

NTA Answer: Option 1(final)

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Lesson: Hyperconjugation

NEET 2020

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following ?

1Hyperconjugation

2−I effect of −CH3 groups

3+R effect of −CH3 groups

4−R effect of −CH3 groups

NTA Answer: Option 1(final)

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Exam traps and common mistakes in this unit

Trap

Carbocation stability order

Category: Similar Terms

Student writes 1° > 2° > 3° (linear with substitution count, but inverted) or treats methyl as more stable.

When it triggers

Question gives multiple carbocations and asks for stability ranking.

How to avoid

Stability: 3° > 2° > 1° > methyl. Hyperconjugation (more α-H = more stable). Resonance can elevate (allyl, benzyl > 1°).

Lesson: Inductive Effect

Trap

Inductive vs resonance / mesomeric effect

Category: Similar Terms

Student treats inductive (through sigma bonds, decreases with distance) like resonance (through pi system, often dominant).

When it triggers

Comparison of substituent effects (acidity, basicity, dipole moment).

How to avoid

Inductive: through-bond, weakens with distance, only sigma. Resonance: through-pi-system, often more powerful, requires conjugation.

Trap

IUPAC nomenclature lowest-locant rule

Category: Similar Terms

Student numbers carbon chain from wrong end, giving higher locants to substituents than necessary.

When it triggers

IUPAC naming question with multiple substituents.

How to avoid

Choose end that gives the LOWEST set of locants for all substituents (compare set, not first-encountered). Functional group has priority for lowest locant.

Trap

Optical vs geometrical isomerism confusion

Category: Similar Terms

Student conflates optical (chirality, R/S) with geometrical (cis/trans). They're different stereoisomerism types.

When it triggers

Question about isomerism of a specific compound.

How to avoid

Optical isomerism requires chiral center (sp³ with 4 different groups). Geometrical isomerism requires restricted rotation (C=C with two different groups on each carbon).

Mistake

Inverts carbocation stability (1° > 3° instead of 3° > 1°).

Root cause: concept gap

Correction

Stability follows hyperconjugation: more α-H → more stable. Order: 3° > 2° > 1° > methyl. Allyl/benzyl resonance-stabilised.

Lesson: Hyperconjugation

Mistake

Claims hyperconjugation possible without alpha hydrogens.

Root cause: concept gap

Correction

Hyperconjugation requires α-C-H bond. tert-Butyl carbocation: 9 α-H → very stable. No-α-H carbocation: no hyperconjugation.

Lesson: Inductive Effect

Mistake

Treats inductive effect like resonance (more powerful, longer-range).

Root cause: concept gap

Correction

Inductive: through sigma, weakens with distance, weak. Resonance: through pi, often dominant for activated systems.

Mistake

Numbers carbon chain from wrong end, giving higher locants than required.

Root cause: rushed under time pressure

Correction

Try numbering from BOTH ends; pick the one giving the lowest SET of locants. Functional group has priority for lowest locant.

Mistake

Confuses optical with geometrical isomerism.

Root cause: concept gap

Correction

Optical: chirality (sp³ with 4 different groups). Geometrical: restricted rotation (C=C). Different molecular features required.

Formulas in this unit

Carbocation stability order

3^{\circ} > 2^{\circ} > 1^{\circ} > CH_{3}^{+}

Stability from hyperconjugation (more α-H) and inductive donation (alkyl groups). Resonance can elevate primary cations.

Symbol	Quantity	SI Unit
stability	relative	-

Valid when

Gas phase or aprotic solvent
Compare similar reaction conditions

NEET question patterns in this unit