1-Iodo-2-nitrobenzene: Properties, Handling & Lab Use Guide

1-Iodo-2-nitrobenzene is an ortho-substituted halogenated aromatic compound widely employed as a versatile electrophilic building block in palladium-catalyzed cross-coupling reactions, nucleophilic aromatic substitution, and the synthesis of complex heterocyclic and pharmaceutical intermediates.

Chemical Name

1-Iodo-2-nitrobenzene

CAS Number

609-73-4

Molecular Formula

C₆H₄INO₂

Molecular Weight

249.01 g/mol

Appearance

Yellow to pale-yellow crystalline solid or liquid (near room temperature)

Key Functional Groups

Aryl iodide (C–I), nitro group (–NO₂)

Primary Applications

Palladium-catalyzed cross-coupling (Suzuki, Sonogashira, Buchwald-Hartwig), nucleophilic aromatic substitution, heterocycle synthesis

Storage Condition

Store in a cool, dry, well-ventilated area away from light and oxidizing agents

Physical and Chemical Properties

1-Iodo-2-nitrobenzene (CAS 609-73-4; MW 249.01 g/mol; molecular formula C₆H₄INO₂) is an ortho-disubstituted benzene ring bearing both an iodo substituent and a nitro group at adjacent positions. The compound typically presents as a yellow to pale-yellow solid or low-melting crystalline material. The electron-withdrawing nitro group positioned ortho to the carbon–iodine bond significantly activates the aromatic ring toward nucleophilic aromatic substitution (SNAr), while simultaneously making the C–I bond an excellent electrophilic site for oxidative addition in transition-metal catalysis.

The C–I bond dissociation energy is considerably lower than that of the analogous C–Br or C–Cl bonds, rendering aryl iodides among the most reactive aryl halides in palladium- and copper-catalyzed coupling chemistries. The combined electronic effects of the iodo and nitro substituents confer distinct reactivity patterns that make this compound a highly selective reagent in multi-step synthesis.

Synthetic Applications and Reactivity

Palladium-Catalyzed Cross-Coupling Reactions: 1-Iodo-2-nitrobenzene is a premier substrate for a broad range of palladium-catalyzed coupling reactions. In Suzuki–Miyaura coupling, it reacts efficiently with arylboronic acids in the presence of a Pd(0) catalyst and base to form biaryl products. In Sonogashira coupling, terminal alkynes are coupled to install alkynyl substituents on the 2-nitrophenyl scaffold. Buchwald–Hartwig amination allows the introduction of amine functionalities, enabling access to ortho-nitroaniline derivatives that serve as precursors to benzimidazoles, indoles, and other nitrogen-containing heterocycles.

Nucleophilic Aromatic Substitution (SNAr): The ortho-nitro group strongly activates the ipso carbon bearing the iodo substituent toward SNAr reactions with hard nucleophiles such as alkoxides, thiolates, and amines under mild conditions. This dual reactivity—metal-catalyzed coupling at C–I and SNAr at the same or adjacent positions—provides synthetic versatility for complex molecule construction.

Heterocycle Synthesis: Reduction of the nitro group followed by intramolecular cyclization is a widely used strategy to construct indoles, benzimidazoles, benzoxazoles, and related heterocycles from 1-iodo-2-nitrobenzene-derived intermediates. The compound serves as a key starting material in pharmaceutical and agrochemical research.

Safe Handling, Storage, and Regulatory Guidance

Hazard Overview: 1-Iodo-2-nitrobenzene is an irritant and should be treated as a potential sensitizer. The nitro aromatic compound class warrants precautionary assessment for reproductive and systemic toxicity; consult the supplier's Safety Data Sheet (SDS) before use.

Personal Protective Equipment (PPE): Wear appropriate chemically resistant gloves (e.g., nitrile), safety goggles or face shield, and a laboratory coat when handling this compound. Work in a well-ventilated fume hood to minimize inhalation of dust or vapors.

Storage: Store in a tightly sealed container in a cool (below 25 °C), dry location away from direct light and incompatible materials such as strong oxidizing agents, reducing agents, and strong bases. Shelf life is maintained under these conditions; inspect for color changes or decomposition before use.

Waste Disposal: Dispose of waste containing 1-iodo-2-nitrobenzene in accordance with local, national, and institutional regulations for halogenated organic waste. Do not pour down the drain.

First Aid: In case of skin or eye contact, flush immediately with copious water for at least 15 minutes and seek medical attention. If inhaled, move the affected person to fresh air. Refer to the current SDS for complete emergency procedures.

Quality, Purity, and Analytical Characterization

For reliable synthetic outcomes, the purity of 1-iodo-2-nitrobenzene is a critical parameter. Research-grade material supplied by Aladdin Scientific (SKU: I136964) is characterized by standard analytical methods to ensure consistent quality.

Recommended Characterization Techniques:

• GC or HPLC purity assay: Gas chromatography or reverse-phase HPLC is routinely used to confirm chemical purity and detect positional isomers (e.g., 1-iodo-3-nitrobenzene or 1-iodo-4-nitrobenzene), which can arise during synthesis or storage.
• ¹H NMR and ¹³C NMR: Nuclear magnetic resonance spectroscopy confirms the ortho substitution pattern. The aromatic proton signals for the 1,2-disubstituted benzene ring appear as a characteristic four-proton pattern in the ¹H NMR spectrum.
• Melting point determination: Consistent melting point within the accepted literature range provides a rapid identity check for the solid compound.
• Mass spectrometry (MS): Confirms the molecular ion at m/z 248/249 consistent with C₆H₄INO₂.

Always request the Certificate of Analysis (CoA) from Aladdin Scientific at the time of purchase to verify lot-specific purity data before use in critical synthetic steps.

Troubleshooting Common Issues in Laboratory Use

Low Coupling Yields: If palladium-catalyzed coupling reactions with 1-iodo-2-nitrobenzene give unexpectedly low yields, first verify reagent purity via GC or HPLC. Moisture, oxygen, and impurities in the aryl iodide feedstock are common culprits. Ensure rigorous Schlenk technique or glovebox handling and use freshly prepared or dried solvents.

Isomeric Impurities: Positional isomers (3-nitro or 4-nitro regioisomers) can complicate downstream reactions or analytical characterization. Use ¹H NMR to confirm the ortho substitution pattern before committing to a large-scale reaction.

Decomposition on Storage: Darkening or solidification of the compound may indicate decomposition. Store under an inert atmosphere (nitrogen or argon) in amber glass vials if long-term storage is required. Discard material that shows significant color change or melting point deviation.

SNAr Side Reactions: When using 1-iodo-2-nitrobenzene in metal-catalyzed couplings, competing SNAr pathways may occur with nucleophilic ligands or amine bases. Select coupling conditions carefully (e.g., use of sterically hindered, non-nucleophilic bases such as Cs₂CO₃ or K₃PO₄) to minimize undesired substitution.

Frequently asked questions

What makes 1-Iodo-2-nitrobenzene more reactive than its bromo or chloro analogues in cross-coupling reactions?

The carbon–iodine bond is significantly weaker and longer than C–Br or C–Cl bonds, enabling faster oxidative addition to the palladium(0) catalyst, which is typically the rate-determining step in cross-coupling catalytic cycles. This translates to milder reaction conditions, lower catalyst loadings, and higher yields compared with the bromo or chloro analogues.

Can 1-Iodo-2-nitrobenzene undergo nucleophilic aromatic substitution (SNAr) under mild conditions?

Yes. The electron-withdrawing nitro group positioned ortho to the iodo substituent strongly activates the ring toward SNAr. This allows nucleophiles such as amines, alkoxides, and thiolates to displace the iodide under relatively mild conditions compared with less-activated aryl halides. Researchers should be aware of this competing pathway when running metal-catalyzed reactions with nucleophilic coupling partners.

How should I confirm the identity and purity of 1-Iodo-2-nitrobenzene received from Aladdin Scientific?

Request the Certificate of Analysis (CoA) for the specific lot number from Aladdin Scientific. For in-house verification, a combination of ¹H NMR (to confirm the ortho disubstitution pattern), GC purity analysis (to detect regioisomeric impurities), and melting point determination against the accepted literature range provides a reliable quality check before use in sensitive synthetic applications.

What are the key safety precautions when working with 1-Iodo-2-nitrobenzene?

Always work in a well-ventilated fume hood wearing nitrile gloves, safety goggles, and a lab coat. Treat the compound as an irritant and potential sensitizer. Consult the current SDS for full hazard information, and dispose of waste as halogenated organic waste in accordance with institutional and local regulations.

What solvents are typically used in reactions with 1-Iodo-2-nitrobenzene?

Common solvents include dimethylformamide (DMF), tetrahydrofuran (THF), dioxane, acetonitrile, and toluene, depending on the reaction type. Suzuki couplings often use aqueous dioxane or DMF/water mixtures, while Sonogashira reactions are frequently carried out in triethylamine or DMF. Solvent choice should be guided by substrate solubility, catalyst compatibility, and the reaction mechanism.

References

1. Negishi, E. (Ed.). Handbook of Organopalladium Chemistry for Organic Synthesis. Wiley-Interscience, 2002. [General reference for palladium-catalyzed cross-coupling of aryl halides]
2. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chemical Reviews, 1995, 95(7), 2457–2483. doi:10.1021/cr00039a007
3. Sonogashira, K. Development of Pd–Cu catalyzed cross-coupling of terminal acetylenes with sp2-carbon halides. Journal of Organometallic Chemistry, 2002, 653(1–2), 46–49. doi:10.1016/S0022-328X(02)01158-0
4. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed. Wiley, 1992. [SNAr reactions of activated aryl halides]

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