4-Bromo-4'-chlorobenzophenone: Properties, Synthesis & Applications

4-Bromo-4'-chlorobenzophenone is a halogen-substituted diaryl ketone widely used as a versatile building block in organic synthesis, pharmaceutical research, and materials science.

Chemical Name

4-Bromo-4'-chlorobenzophenone

CAS Number

500-00-5

Molecular Formula

C₁₃H₈BrClO

Molecular Weight

295.56 g/mol

SKU

B152251

Functional Class

Halogenated diaryl ketone / synthetic intermediate

Chemical Identity and Physical Properties

4-Bromo-4'-chlorobenzophenone (CAS 500-00-5) is an unsymmetrically halogenated benzophenone bearing a bromine substituent on one phenyl ring and a chlorine substituent on the other, with a carbonyl (C=O) bridge connecting the two aromatic rings. Its molecular formula is C₁₃H₈BrClO and its molecular weight is approximately 295.56 g/mol.

The compound typically presents as a white to off-white crystalline solid at room temperature. The presence of two different halogen atoms endows the molecule with distinct reactivity at each aryl position, making it particularly attractive for selective cross-coupling and nucleophilic substitution chemistry. The carbonyl group contributes a strong IR absorption near 1660–1680 cm⁻¹, characteristic of conjugated aryl ketones.

Note: Specific melting point, boiling point, and solubility data should be confirmed against the current certificate of analysis (CoA) supplied with SKU B152251.

Synthesis and Preparation Methods

The most established route to 4-bromo-4'-chlorobenzophenone is Friedel-Crafts acylation. In a representative approach, 4-bromobenzoyl chloride (or the corresponding acid anhydride) is reacted with chlorobenzene in the presence of a Lewis acid catalyst such as aluminum chloride (AlCl₃). The electrophilic aromatic substitution preferentially installs the acyl group at the para position of chlorobenzene, driven by the directing effects of the existing chloro substituent.

Alternative disconnections include:

• Oxidation of the corresponding diarylmethanol or diarylmethane using oxidants such as potassium permanganate or chromium-based reagents.
• Metal-mediated carbonylation between an aryl halide and a carbon monoxide source, though such routes are less common for this specific substrate.

Careful control of stoichiometry and reaction temperature is essential to minimize di-acylation by-products and to achieve high regioselectivity. Researchers are advised to consult primary literature for optimized conditions before scaling reactions.

Applications in Research and Synthesis

The dual halogenation pattern of 4-bromo-4'-chlorobenzophenone makes it an exceptionally versatile intermediate in modern synthetic chemistry:

• Cross-coupling chemistry: The C–Br bond is significantly more reactive than C–Cl toward oxidative addition to palladium(0) and nickel(0) catalysts. This selectivity allows chemoselective Suzuki-Miyaura, Negishi, Sonogashira, or Buchwald-Hartwig couplings to be performed preferentially at the bromide site, while the chloride remains available for a subsequent orthogonal transformation.
• Pharmaceutical and agrochemical intermediates: Benzophenone scaffolds are found in several drug classes and crop-protection agents. The halogenated variant serves as a building block for medicinal chemistry programs targeting diverse biological pathways.
• Polymer and materials science: Benzophenone derivatives are exploited as UV-absorbers and photoinitiators. Halogen-functionalized analogues can be incorporated into polymer backbones or used to tailor photophysical properties.
• Ligand and catalyst synthesis: The ketone and halide handles allow elaboration into chiral ligands, bidentate phosphines, and N-heterocyclic carbene precursors relevant to asymmetric catalysis.

The orthogonal reactivity of bromine versus chlorine at the two aryl rings is the key synthetic advantage of this compound over symmetrically dihalogenated benzophenones.

Handling, Safety, and Storage

As with all halogenated aromatic ketones, appropriate laboratory safety practices should be observed when working with 4-bromo-4'-chlorobenzophenone:

• Personal protective equipment (PPE): Wear nitrile gloves, safety goggles, and a lab coat. Work in a well-ventilated fume hood to avoid inhalation of dust or vapors.
• Storage: Store in a tightly sealed container in a cool, dry location away from incompatible materials such as strong oxidizers and strong bases. Typical storage temperature is room temperature or below; confirm with the product CoA.
• Disposal: Dispose of waste in accordance with local, national, and institutional regulations for halogenated organic waste.
• First aid: In case of skin or eye contact, flush with copious water and seek medical attention if irritation persists.

Always consult the current Safety Data Sheet (SDS) for SKU B152251 before use. The SDS provides authoritative hazard classification, exposure limits, and emergency procedures.

Product Specifications and Quality

Aladdin Scientific offers 4-bromo-4'-chlorobenzophenone under SKU B152251. Researchers and procurement teams should reference the current product page and certificate of analysis for up-to-date specifications, including:

• Purity grade and analytical method (e.g., GC or HPLC purity %)
• Available pack sizes and pricing
• Batch-specific NMR, MS, or elemental analysis data
• Appearance and physical form

For custom quantities, bulk orders, or additional analytical documentation, contact Aladdin Scientific's technical sales team. All products are subject to Aladdin Scientific's standard quality-control procedures.

Frequently asked questions

What makes 4-Bromo-4'-chlorobenzophenone useful in cross-coupling reactions?

The molecule contains two different carbon–halogen bonds: C–Br and C–Cl. Because C–Br bonds undergo oxidative addition to Pd(0) and Ni(0) catalysts much faster than C–Cl bonds, chemists can selectively functionalize the bromide position first and reserve the chloride for a second, distinct coupling step. This orthogonal reactivity enables efficient two-step diversification from a single starting material.

How should 4-Bromo-4'-chlorobenzophenone be stored to maintain purity?

The compound should be stored in a tightly sealed container in a cool, dry environment, away from strong oxidizers, strong bases, and direct light. Confirm the recommended temperature range on the certificate of analysis supplied with SKU B152251. Proper sealing prevents moisture uptake and potential slow hydrolysis of the carbonyl functionality under harsh conditions.

Can 4-Bromo-4'-chlorobenzophenone be used as a photoinitiator?

Benzophenone and its derivatives are well known for their ability to absorb UV light and generate reactive triplet states that initiate radical polymerization. While unsubstituted benzophenone is the classic photoinitiator, halogenated analogues such as 4-bromo-4'-chlorobenzophenone may serve as precursors or structural components in the development of novel photoinitiator systems. Their direct use as photoinitiators should be validated experimentally, as halogen substitution alters the photophysical properties relative to the parent compound.

What analytical methods are used to confirm the purity of this compound?

Common analytical techniques for characterizing 4-bromo-4'-chlorobenzophenone include gas chromatography (GC) or high-performance liquid chromatography (HPLC) for purity determination, proton and carbon NMR spectroscopy for structural confirmation, and mass spectrometry for molecular weight verification. The specific methods applied by Aladdin Scientific are detailed on the batch certificate of analysis for SKU B152251.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley: New York, 1992. (Friedel-Crafts acylation, general reference)
2. Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95, 2457–2483. doi:10.1021/cr00039a007
3. Larock, R. C. Comprehensive Organic Transformations, 2nd ed.; Wiley-VCH: New York, 1999. (General synthetic reference for diaryl ketones)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.