Chemical Identity and Physical Properties

4-Chloro-3-iodobenzoic acid (CAS 6578-75-2) is an aromatic carboxylic acid bearing two different halogen substituents on the benzene ring: a chlorine atom at the 4-position and an iodine atom at the 3-position, with the carboxylic acid group at the 1-position. Its molecular formula is C₇H₄ClIO₂ and its molecular weight is approximately 282.46 g/mol.

The compound typically appears as a white to off-white crystalline solid at room temperature. The presence of two electron-withdrawing halogens and a carboxylic acid group makes the aromatic ring electron-deficient, influencing its reactivity in nucleophilic aromatic substitution and electrophilic metalation reactions. The carboxylic acid functionality also enables salt formation and esterification, expanding the range of accessible derivatives.

Recommended storage conditions are in a cool, dry, well-ventilated location away from incompatible materials such as strong oxidizers and strong bases. Specific melting point data should be confirmed against the Certificate of Analysis supplied with SKU C135910.

Synthetic Applications and Reactivity

The defining synthetic value of 4-Chloro-3-iodobenzoic acid lies in its two chemically distinct C–halogen bonds. The C–I bond is substantially more reactive than C–Cl in oxidative addition to palladium(0) complexes, enabling highly selective, sequential functionalization strategies.

Palladium-catalyzed cross-coupling: The aryl iodide site undergoes preferential oxidative addition under standard Suzuki–Miyaura, Sonogashira, Heck, or Negishi conditions. This selectivity allows the C–Cl bond to be preserved as a handle for a subsequent orthogonal coupling step, providing access to unsymmetrical polyaryl or aryl–alkynyl architectures from a single scaffold.

Directed metalation: The carboxylic acid (or its amide derivatives) can act as a directed metalation group (DMG), facilitating regioselective lithiation ortho to the directing group under cryogenic conditions, followed by trapping with electrophiles to introduce additional functionality.

Pharmaceutical and agrochemical synthesis: Bifunctionally halogenated benzoic acid building blocks are widely employed in medicinal chemistry campaigns, where the carboxylic acid serves as a handle for amide bond formation and the halogens enable C–C or C–heteroatom bond construction. The compound is therefore useful for generating diverse lead compound libraries.

Reagent Specifications and Quality Considerations

When sourcing 4-Chloro-3-iodobenzoic acid for research applications, several quality attributes deserve careful attention:

• Purity: For sensitive catalytic reactions, high purity (≥97% by HPLC or GC) is recommended to avoid catalyst poisoning and to ensure reproducible yields. Refer to the Certificate of Analysis for SKU C135910 for the lot-specific purity value.
• Appearance: The material should be a free-flowing white to off-white crystalline powder. Discoloration may indicate partial degradation or impurities.
• Moisture sensitivity: Although not classified as highly moisture-sensitive, storage under inert atmosphere is advisable for long-term preservation of purity, particularly for material intended for demanding organometallic transformations.
• Packaging: Aladdin Scientific offers SKU C135910 in research quantities; consult the product page for available pack sizes and pricing.

Researchers should always verify the specific purity, melting point and spectral data against the provided CoA before use in critical experiments.

Safety and Handling Guidelines

4-Chloro-3-iodobenzoic acid should be handled in accordance with good laboratory practice (GLP) and applicable local regulations. Key precautions include:

• Personal Protective Equipment (PPE): Wear chemically resistant gloves, a laboratory coat, and safety glasses when handling the solid or solutions. Use a dust mask or work in a fume hood if powder generation is likely.
• Inhalation and ingestion: Avoid inhaling dust and ingesting the compound. Halogenated aromatic compounds may be irritating to mucous membranes and the respiratory tract.
• Skin and eye contact: In case of contact, wash thoroughly with water for at least 15 minutes and seek medical advice if irritation persists.
• Disposal: Dispose of waste material in accordance with local environmental regulations for halogenated organic waste. Do not pour into drains or water courses.
• Storage: Store in a tightly sealed container in a cool, dry location (recommended 2–8 °C for long-term storage) away from heat sources, oxidizers, and strong bases.

Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific for complete hazard classification, GHS pictograms, and emergency response information specific to SKU C135910.