Definition
Electrophiles and nucleophiles
Electrophile (E⁺): electron-pair acceptor (Lewis acid). Examples: H⁺, Cl⁺, NO₂⁺, BF₃. Nucleophile (Nu⁻): electron-pair donor (Lewis base). Examples: OH⁻, CN⁻, NH₃, H₂O.
-- NCERT, p. 32Electrophiles Nucleophiles
8 MCQs9-step worked example
Source: NCERT Alcohols, Phenols and EthersPYQ coverage: NEET 2021, 2022, 2023, 2024, 2025Official key: NTA-verifiedLast reviewed: May 2026
Lesson
The trap: Students treat electrophiles and nucleophiles as mirror categories distinguished only by charge. They forget that the defining feature is the electron-density site — not whether the species is positive or negative overall. A neutral molecule with an electron-deficient atom (like BF₃ or AlCl₃) is an electrophile; a neutral molecule with a lone pair available for donation (like NH₃ or H₂O) is a nucleophile.
Core definitions (NCERT Class 11 Chemistry, Chapter 9, page 32):
An electrophile ("electron-loving") is any species that accepts an electron pair to form a new covalent bond. It has either a positive charge or an electron-deficient atom. Examples: H⁺, NO₂⁺, BF₃, carbocations, AlCl₃.
A nucleophile ("nucleus-loving") is any species that donates an electron pair to form a new covalent bond. It has either a negative charge or a lone pair available for donation. Examples: OH⁻, CN⁻, NH₃, H₂O, R-NH₂.
Key distinction for NEET:
The inductive effect matters here. When comparing nucleophilic or electrophilic strength, students confuse the through-sigma-bond inductive pathway with through-pi resonance effects. Inductive effect operates through sigma bonds and weakens with distance; resonance operates through the pi system and is often dominant. A species can be simultaneously an electrophile at one site and bear a partial negative elsewhere — what matters is which atom participates in bond formation.
Watch-out: NEET often gives neutral species and asks whether they're electrophilic or nucleophilic. Focus on the reactive atom: does it have a vacant orbital or electron deficiency (electrophile) or a donatable lone pair (nucleophile)?
Practice MCQs
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
MCQ 1Easy RecallPractice
Which of the following is an electrophile?
MCQ 2Easy RecallPractice
Which of the following species can act as both an electrophile and a nucleophile?
MCQ 3Direct ApplicationPractice
The electrophilic character of a carbonyl carbon (C=O) is primarily due to:
MCQ 4Direct ApplicationPractice
Among the following, which is the strongest nucleophile in a protic solvent?
MCQ 5Easy RecallPractice
Which of the following correctly distinguishes an electrophile from a nucleophile?
MCQ 6Direct ApplicationPractice
AlCl₃ acts as an electrophile in Friedel-Crafts reactions because:
MCQ 7Concept TrapPractice
Consider the following species: (i) NO₂⁺, (ii) CN⁻, (iii) CH₂=CH₂, (iv) NH₃. How many of these can act as nucleophiles?
MCQ 8Direct ApplicationPractice
The inductive effect differs from the resonance effect in that the inductive effect:
Worked Example
- 1
Given
The following species are presented: (a) CH₃OH, (b) BF₃, (c) NO₂⁺, (d) C₂H₅NH₂. Classify each as electrophile, nucleophile, or ambident (can act as both).
- 2
Required
Identify the electron-pair donor/acceptor character of each species.
- 3
Concept
An electrophile has an electron-deficient centre (empty orbital, positive charge, or incomplete octet). A nucleophile has a lone pair or pi electrons available for donation. Some species are ambident.
- 4
Formula/Rule
Classification rule: Check the reactive atom — vacant orbital → electrophile; available lone pair → nucleophile; both features at different sites → ambident.
- 5
Substitution/Analysis
- CH₃OH: Oxygen has two lone pairs → can donate → nucleophilic. However, the O-H bond is also polarised (H is electrophilic). Ambident. - BF₃: Boron has only 6 valence electrons, vacant p-orbital → electrophile. - NO₂⁺: Nitrogen is electron-deficient (positive charge, needs electrons) → electrophile. - C₂H₅NH₂: Nitrogen has a lone pair → nucleophile.
- 6
Calculation
No arithmetic needed — this is classification by electronic structure analysis.
- 7
Final answer
- CH₃OH → ambident (nucleophile via O lone pair; electrophile via H) - BF₃ → electrophile - NO₂⁺ → electrophile - C₂H₅NH₂ → nucleophile
- 8
Common trap
Students classify all neutral molecules as "neither electrophile nor nucleophile." Neutrality does not preclude electrophilic or nucleophilic character — the relevant criterion is whether the reactive atom has a vacant orbital or donatable lone pair. BF₃ is neutral yet strongly electrophilic. NH₃ is neutral yet nucleophilic.
- 9
Similar NEET-style question
"Among BeCl₂, CCl₄, NH₃, and H₂O, identify the species that act as Lewis acids (electrophiles)." Answer: BeCl₂ (Be has incomplete octet — only 4 valence electrons in the molecule, vacant p-orbital). ---
Before solving, remember these
Formulas
Carbocation stability order
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
Exam Traps & Common Mistakes
These are the exact patterns that cause wrong answers in NEET. Each trap includes when it triggers and how to avoid it.
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°).
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.
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.
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).
Root cause: concept gap
Correction
Stability follows hyperconjugation: more α-H → more stable. Order: 3° > 2° > 1° > methyl. Allyl/benzyl resonance-stabilised.
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.
Root cause: concept gap
Correction
Inductive: through sigma, weakens with distance, weak. Resonance: through pi, often dominant for activated systems.
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.
Root cause: concept gap
Correction
Optical: chirality (sp³ with 4 different groups). Geometrical: restricted rotation (C=C). Different molecular features required.
Past Year Questions
11 questions from NEET 2021, 2022, 2023, 2024, 2025. Answers verified against NTA official keys.
NEET 2025
Which one of the following compounds can exist as cis-trans isomers?
11, 2-Dimethylcyclohexane
2Pent-1-ene
32-Methylhex-2-ene
41, 1-Dimethylcyclopropane
NTA Answer: Option 1(final)
NEET 2025
1II > III > I
2II > I > III
3I > II > III
4III > II > I
NTA Answer: Option 2(final)
NEET 2025
1A, C and D only
2B and E only
3A and C only
4D and E only
NTA Answer: Option 3(final)
NEET 2024Revised key
A compound with a molecular formula of C H has two tertiary carbons. Its IUPAC name is : 6 14
1n-hexane
22-methylpentane
32,3-dimethylbutane
42,2-dimethylbutane
NTA Answer: Option 3(revised_final)
NEET 2024Revised key
1Three resonance structures can be drawn for ozone
2BF has non-zero dipole moment 3
3Dipole moment of NF is greater than that of NH 3 3
4Three canonical forms can be drawn for CO2− ion 3
NTA Answer: Option 4(revised_final)
NEET 2024Revised key
1propylamine
2butylamine
3butanamide
4–bromobutanoic acid
NTA Answer: Option 1(revised_final)
NEET 2023
1H = U + n g RT
2H – U = –nRT
3H + U = nR
4H = U – n RT g
NTA Answer: Option 1(final)
NEET 2022
The incorrect statement regarding chirality is
1A racemic mixture shows zero optical rotation
2S 1 reaction yields 1 : 1 mixture of both enantiomers N
3The product obtained by S 2 reaction of haloalkane having chirality at the reactive site shows inversion N of configuration
4Enantiomers are superimposable mirror images on each other
NTA Answer: Option 4(final)
NEET 2022
10.2303
21.3818
30.9212
40.4606
NTA Answer: Option 3(final)
NEET 2022
The correct IUPAC name of the following compound is
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)
NEET 2021
1(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
2(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
3(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
4(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
NTA Answer: Option 1(final)
How NEET usually asks this
Recurring question shapes from past papers. Each pattern shows why wrong options look tempting.
Order carbocations by stability. 3° > 2° > 1° > methyl. Allyl/benzyl extra stabilised by resonance.
InterpretationEasy
Common distractors
ignores resonance
Compares only by alkyl substitution
Sources
NCERT refs: Class 11 Chemistry Chapter 9, p.32
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