Directive Influence

8 MCQs9-step worked example

Source: NCERT Aldehydes, Ketones and Carboxylic AcidsPYQ coverage: NEET 2021, 2022, 2023, 2024, 2025Official key: NTA-verifiedLast reviewed: May 2026

Lesson

The trap that costs marks here: confusing which substituents direct incoming electrophiles to ortho/para positions versus meta positions — and forgetting the anomaly of halogens.

When a monosubstituted benzene undergoes electrophilic aromatic substitution (EAS), the existing substituent controls two things: (1) the position where the new group enters (ortho/para or meta), and (2) whether the ring is activated (reacts faster than benzene) or deactivated (reacts slower).

Ortho/para directors and activators: Groups that donate electron density into the ring by resonance or hyperconjugation — –OH, –OR, –NH₂, –NHR, –NR₂, –NHCOCH₃, and alkyl groups (–CH₃, –C₂H₅). These increase electron density at ortho and para positions, stabilising the intermediate arenium ion (NCERT Class 11 Chemistry, Chapter 13, page 28).

Meta directors and deactivators: Groups that withdraw electron density — –NO₂, –CN, –COOH, –CHO, –COR, –SO₃H. These destabilise the arenium ion at ortho/para positions, making meta substitution the least unfavourable path.

The halogen anomaly: –F, –Cl, –Br, –I are ortho/para directors (lone-pair resonance donation to ortho/para carbons) but deactivators (strong inductive withdrawal dominates the overall rate). This combination — o,p-directing yet deactivating — is the single most tested exception in NEET EAS questions.

How to think about it in the exam: First classify the substituent: electron-donating resonance → o,p-activator; electron-withdrawing resonance/induction → m-deactivator; halogen → o,p but deactivating. Then draw the major product at the ortho or para position (para usually dominates due to steric preference, unless the question specifies otherwise).

Watch out: a common confusion is classifying halogens as meta directors because they are deactivators. The directing effect (resonance) and the activation effect (induction) are governed by different electronic mechanisms — they need not agree.

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 groups is an ortho/para director in electrophilic aromatic substitution?

MCQ 2Easy RecallPractice

Halogens attached to a benzene ring are:

MCQ 3Easy RecallPractice

Which of the following is a meta-directing group in electrophilic aromatic substitution?

MCQ 4Direct ApplicationPractice

Nitration of toluene (methylbenzene) gives predominantly:

MCQ 5Direct ApplicationPractice

When chlorobenzene undergoes Friedel-Crafts alkylation, the major product is:

MCQ 6Direct ApplicationPractice

Aniline (C₆H₅NH₂) is treated with bromine water. The expected product is:

MCQ 7Concept TrapPractice

Among the following monosubstituted benzenes, which undergoes electrophilic substitution fastest? (I) C₆H₅OCH₃ (II) C₆H₅NO₂ (III) C₆H₅Cl (IV) C₆H₅CH₃

MCQ 8CalculationPractice

Predict the major product when p-cresol (4-methylphenol) is treated with one equivalent of bromine in acetic acid.

Worked Example

1
Given
- Starting material: nitrobenzene (C₆H₅NO₂) - Reagent: conc. HNO₃ + conc. H₂SO₄ (nitrating mixture) - Reaction type: electrophilic aromatic substitution (nitration)
2
Required
Major product of nitration of nitrobenzene.
3
Concept
The existing –NO₂ group is a meta director and a strong deactivator. It withdraws electron density from ortho/para positions (–M and –I effects), making the meta position the least destabilised site for electrophilic attack.
4
Formula / Rule
Meta-directing rule: electron-withdrawing groups with –M effect direct incoming electrophiles to the meta position.
5
Substitution / Application
–NO₂ on ring → meta director → incoming –NO₂ goes to the meta position (position 3 relative to existing –NO₂ at position 1).
6
Calculation
No arithmetic needed. This is a classification + directing-effect application. Identify the substituent type (EWG, meta director) → predict position (meta).
7
Final answer
The major product is **m-dinitrobenzene** (1,3-dinitrobenzene). Note: The reaction is slow because –NO₂ strongly deactivates the ring, requiring harsher conditions than nitration of benzene.
8
Common trap
A student who confuses meta directors with ortho/para directors might predict o- or p-dinitrobenzene. The key check: –NO₂ withdraws electrons → meta director. This is the same confusion documented as the aromatic director confusion mistake — misclassifying EWGs as o,p-directors.
9
Similar NEET-style question
"Predict the major product when benzoic acid (C₆H₅COOH) undergoes sulfonation." (Answer: m-sulfobenzoic acid, because –COOH is a meta director.) ---

Before solving, remember these

Key Fact

Directive influence (ortho/para vs meta)

Ortho/para directors (also activators except halogens): -OH, -OR, -NH₂, -NHR, -NR₂, -NHCOR, alkyl, halogens (deactivating). Meta directors (deactivators): -NO₂, -CN, -SO₃H, -CHO, -COR, -COOH.

-- NCERT, p. 28

Formulas

Markovnikov's rule (and anti-Markovnikov)

H^{+} to C with more H

Without peroxide: ionic mechanism — H goes to carbon with MORE hydrogens (carbocation stability rule). With peroxide (HBr only, Kharasch): radical mechanism — anti-Markovnikov.

Symbol	Quantity	SI Unit
H,X	added atoms	-

Valid when

Asymmetric alkene
H-X with X = Cl, Br, I
Without peroxide for Markovnikov

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.

Trap

Markovnikov reverses with peroxide

Category: Organic Reaction Conditions

HBr addition to alkene: WITHOUT peroxide → Markovnikov (H to C with more H). WITH peroxide (Kharasch effect) → anti-Markovnikov (radical mechanism). Specific to HBr only — not HCl, HI.

When it triggers

Question gives HX addition to alkene with explicit peroxide condition or hints (e.g. ROOR, light).

How to avoid

Without peroxide: ionic mechanism, carbocation stability → Markovnikov. With peroxide: radical mechanism, radical stability → anti-Markovnikov. Effect ONLY for HBr (HCl too strong, HI too weak).

Trap

Solvent changes product distribution

Category: Organic Reaction Conditions

Same starting materials give different products depending on solvent. Polar protic (water, alcohols): SN1/E1 favoured. Polar aprotic (DMSO, DMF): SN2 favoured. Affects substitution vs elimination.

When it triggers

Question contrasts product when solvent is changed; or specifies solvent type.

How to avoid

Polar protic stabilises carbocation → SN1/E1 (3° preferred). Polar aprotic doesn't solvate nucleophile → strong SN2 nucleophile (1°/2° preferred). Bulky base (t-BuOK) favours E2 over SN2.

Mistake

Confuses ortho/para directors with meta directors.

Root cause: concept gap

Correction

o,p-directors (activators except halogens): -OH, -OR, -NH₂, -NHR, alkyl. m-directors (deactivators): -NO₂, -CN, -COOH, -CHO. Halogens: o,p-directors but DEACTIVATORS.

Mistake