Chemistry · JEE Advanced only

Haloarenes: Fittig, Wurtz-Fittig and Nucleophilic Aromatic Substitution (JEE Advanced)

Not in the JEE Main syllabus, but it is in JEE Advanced. Study time: about 2-3 hours. The reactions are straightforward once you understand the mechanisms. Spend time on SNAr mechanism and practicing reactivity comparisons..

Last updated: 26 October 2026

Direct answer

Haloarenes undergo special coupling reactions (Fittig and Wurtz-Fittig) using sodium metal to form biphenyls or alkylbenzenes.

Haloarenes undergo special coupling reactions (Fittig and Wurtz-Fittig) using sodium metal to form biphenyls or alkylbenzenes. They also undergo nucleophilic aromatic substitution (SNAr) when electron-withdrawing groups are present, replacing the halogen with nucleophiles like OH⁻ or NH₂⁻ under harsh conditions.

Official syllabus

What the JEE Advanced syllabus says

“Reactions: Fittig, Wurtz-Fittig; Nucleophilic aromatic substitution in haloarenes and substituted haloarenes (excluding benzyne mechanism and cine substitution)”

Source: JEE Advanced 2026 Information Bulletin, Annexure-I. Closest JEE Main topic: General methods of preparation, properties and reactions, nature of C-X bond.

JEE Main covers basic haloarene properties and the C-X bond nature, but stops there. Advanced specifically tests these named reactions and the SNAr mechanism, which require understanding of how electron-withdrawing groups activate the ring toward nucleophilic attack.

Key ideas

What you must understand

Fittig reaction: 2 ArX + 2Na → Ar-Ar + 2NaX (two aryl halides couple to form biphenyl)
Wurtz-Fittig reaction: ArX + RX + 2Na → Ar-R + 2NaX (aryl halide couples with alkyl halide to give alkylbenzene)
In Wurtz-Fittig, the alkyl-alkyl coupling (Wurtz product) also forms as a side product
SNAr requires electron-withdrawing groups (NO₂, CN) ortho or para to the halogen to stabilize the intermediate
SNAr mechanism: addition of nucleophile forms a resonance-stabilized carbanion (Meisenheimer complex), then halide leaves
More EWGs = faster SNAr; 2,4-dinitro is faster than mono-nitro; 2,4,6-trinitro is fastest

Formulas

Formulas and key facts

Fittig: 2C₆H₅Br + 2Na → C₆H₅-C₆H₅ + 2NaBr
Wurtz-Fittig: C₆H₅Br + CH₃Br + 2Na → C₆H₅CH₃ + 2NaBr
SNAr rate order: F > Cl > Br > I (opposite to SN2, because C-F bond is most polar)
2,4-dinitrochlorobenzene + NaOH → 2,4-dinitrophenol + NaCl
Meisenheimer complex: sp³ carbon bearing nucleophile, stabilized by resonance with NO₂ groups
Reactivity for SNAr: 2,4,6-trinitro > 2,4-dinitro > p-nitro > m-nitro (meta is slowest)
Picryl chloride (2,4,6-trinitrochlorobenzene) reacts with water alone at room temperature

Avoid

Common mistakes

Confusing SNAr halogen reactivity (F > Cl > Br > I) with SN2 order (I > Br > Cl > F). In SNAr, the rate-determining step is nucleophile addition, not halide departure.
Forgetting that meta-EWG does not activate SNAr because it cannot stabilize the negative charge in the Meisenheimer complex by resonance.
In Wurtz-Fittig, writing only the cross-coupled product. The Wurtz product (R-R) also forms as a byproduct.
Assuming SNAr works on plain chlorobenzene. Without activating EWGs, nucleophilic substitution needs extreme conditions or proceeds via benzyne (which is excluded from syllabus).

Worked example

A JEE Advanced-level example

Question. Arrange the following in decreasing order of reactivity toward nucleophilic aromatic substitution with NaOH: (A) p-nitrochlorobenzene, (B) 2,4-dinitrochlorobenzene, (C) chlorobenzene, (D) 2,4,6-trinitrochlorobenzene

Show solution

SNAr reactivity depends on how well the Meisenheimer intermediate is stabilized by EWGs.
More NO₂ groups at ortho/para positions = more resonance stabilization = faster reaction.
2,4,6-trinitro (D) has three NO₂ groups stabilizing the intermediate.
2,4-dinitro (B) has two NO₂ groups at ortho and para positions.
p-nitro (A) has one NO₂ group at para position.
Chlorobenzene (C) has no EWG, so SNAr is extremely slow (essentially unreactive under normal conditions).

Answer: D > B > A > C

Solved twice independently; both solutions agree.

FAQs

Frequently asked questions

Is Haloarenes: Fittig, Wurtz-Fittig and Nucleophilic Aromatic Substitution in the JEE Main syllabus?

No. It is in the JEE Advanced 2026 syllabus only. The closest JEE Main topic is General methods of preparation, properties and reactions, nature of C-X bond.

How long does Haloarenes: Fittig, Wurtz-Fittig and Nucleophilic Aromatic Substitution take to prepare for JEE Advanced?

About 2-3 hours. The reactions are straightforward once you understand the mechanisms. Spend time on SNAr mechanism and practicing reactivity comparisons., if you already know the related JEE Main topic.