2,4-Difluorobenzoyl Chloride: Handling & Synthetic Use Guide
2,4-Difluorobenzoyl Chloride: Handling & Synthetic Use Guide
2,4-Difluorobenzoyl Chloride is a reactive, fluorine-substituted aromatic acyl chloride widely employed as an electrophilic acylating agent in pharmaceutical intermediate synthesis, Friedel-Crafts reactions, and the preparation of esters, amides, and other carbonyl derivatives.
- CAS Number
- 2366-88-3
- Molecular Formula
- C₇H₃ClF₂O
- Molecular Weight
- 177.00 g/mol
- Appearance
- Colorless to pale yellow liquid
- Reactivity
- Reacts vigorously with water, alcohols, and amines; moisture-sensitive
- Storage Condition
- Store under inert atmosphere, sealed, in a cool and dry place away from moisture
- SKU
- D134834
Chemical Identity and Properties
2,4-Difluorobenzoyl Chloride (CAS 2366-88-3) is an aromatic acyl chloride bearing two fluorine substituents at the 2- and 4-positions of the benzene ring. Its molecular formula is C₇H₃ClF₂O with a molecular weight of approximately 177.00 g/mol. The compound presents as a colorless to pale yellow liquid under standard conditions.
The electron-withdrawing nature of the two fluorine atoms reduces the electron density of the aromatic ring and the carbonyl group, modulating the electrophilicity of the acyl chloride functionality. This electronic profile makes it a versatile building block in the preparation of fluorinated pharmaceuticals and agrochemicals, where the fluorine atoms can contribute to improved metabolic stability, lipophilicity, and membrane permeability of target molecules.
The C–F bonds at the 2- and 4-positions are stable under most synthetic conditions, while the acyl chloride moiety retains high reactivity toward nucleophiles, including amines, alcohols, and water.
Synthetic Applications
2,4-Difluorobenzoyl Chloride serves as a key electrophilic acylating agent in a broad range of organic transformations:
- Friedel-Crafts Acylation: In the presence of a Lewis acid catalyst such as AlCl₃, the reagent undergoes electrophilic aromatic substitution to introduce the 2,4-difluorobenzoyl group onto electron-rich arenes, enabling rapid access to diaryl ketone frameworks common in drug discovery.
- Amide Bond Formation: Reaction with primary or secondary amines (typically in the presence of a base such as triethylamine to neutralize the generated HCl) affords 2,4-difluorobenzamide derivatives. These amide products are valuable intermediates in the synthesis of fluoroquinolone antibiotics, kinase inhibitors, and other bioactive agents.
- Esterification: Alcohols react with 2,4-Difluorobenzoyl Chloride under mild conditions to give the corresponding esters, useful as protecting groups or pharmacophoric units.
- Schotten-Baumann Conditions: Biphasic aqueous/organic acylation using dilute NaOH as the base can be employed for the acylation of amines and phenols while minimizing hydrolysis side reactions.
The fluorine substituents are frequently retained in the final target molecules to leverage their favorable pharmacokinetic effects, making this reagent particularly attractive for medicinal chemistry programs.
Safe Handling and Storage Guidelines
As with all acyl chlorides, 2,4-Difluorobenzoyl Chloride requires careful handling due to its reactivity with moisture and its corrosive, lachrymatory nature. The following precautions are essential:
- Personal Protective Equipment (PPE): Always wear chemical-splash goggles, a face shield, acid-resistant gloves (e.g., butyl rubber or neoprene), and a lab coat. Work in a well-ventilated fume hood at all times.
- Moisture Exclusion: The reagent hydrolyzes rapidly on contact with atmospheric moisture to generate 2,4-difluorobenzoic acid and HCl gas. All transfers and reactions should be carried out under an inert atmosphere (nitrogen or argon) using oven-dried glassware and syringes.
- Waste Disposal: Excess reagent and reaction waste containing acyl chloride residues should be quenched carefully with a dilute aqueous base (e.g., sodium bicarbonate solution) before disposal as halogenated organic waste in accordance with local regulations.
- Storage: Store in tightly sealed containers under an inert atmosphere in a cool, dry location. Segregate from water, alcohols, amines, and oxidizers. Recommended storage temperature is 2–8 °C or as specified on the product label.
- First Aid: In case of skin or eye contact, flush immediately with copious amounts of water for at least 15 minutes and seek medical attention. If inhaled, move to fresh air immediately.
Quality, Purity, and Specification Considerations
For synthetic and research applications, reagent purity is a critical parameter. Key quality considerations for 2,4-Difluorobenzoyl Chloride (SKU: D134834) include:
- Purity Assessment: Typical analytical methods for acyl chloride purity include GC (gas chromatography) and titration-based assays. Researchers should confirm the purity specification on the certificate of analysis (CoA) provided with each lot.
- Common Impurities: Potential impurities include the parent 2,4-difluorobenzoic acid (from partial hydrolysis), unreacted thionyl chloride or oxalyl chloride residues (if those reagents were used in synthesis), and isomeric benzoyl chlorides. These impurities can negatively affect yield and product purity in downstream reactions.
- Lot-to-Lot Consistency: For regulated research or process development, request batch-specific CoA documentation confirming identity (NMR, IR), purity (GC), and water content (Karl Fischer titration).
- Packaging Integrity: Upon receipt, inspect the container for seal integrity. Discoloration or cloudiness may indicate moisture ingress and compromised quality.
Contact Aladdin Scientific technical support for custom purity grades or bulk quantity requirements.
Frequently asked questions
What is the best way to transfer 2,4-Difluorobenzoyl Chloride in the laboratory?
Transfer should always be performed in a dry, inert-atmosphere fume hood using oven-dried syringes or cannulas under a nitrogen or argon blanket. Avoid exposure to atmospheric moisture, as the reagent hydrolyzes rapidly to generate corrosive HCl gas. Cap the stock container immediately after use and re-seal under inert gas.
Can 2,4-Difluorobenzoyl Chloride be used for large-scale amide coupling reactions?
Yes, it is suitable for scale-up amide coupling. For larger scales, Schotten-Baumann conditions (biphasic aqueous/organic system with aqueous base) are often preferred to control exothermicity and facilitate workup. Ensure adequate cooling and gas-scrubbing systems are in place to manage HCl evolution safely during scale-up.
How should I dispose of excess 2,4-Difluorobenzoyl Chloride after an experiment?
Excess reagent should be quenched by careful, slow addition to a stirred dilute aqueous sodium bicarbonate solution in a fume hood, which neutralizes HCl and hydrolyzes the acyl chloride. The resulting aqueous mixture should then be disposed of as halogenated organic chemical waste in accordance with your institution's and local regulatory requirements.
What solvents are compatible with 2,4-Difluorobenzoyl Chloride in synthesis?
Aprotic solvents such as dichloromethane (DCM), tetrahydrofuran (THF), toluene, diethyl ether, and acetonitrile are generally compatible. Protic solvents (water, methanol, ethanol) should be avoided as they react directly with the acyl chloride, causing hydrolysis or solvolysis and consuming the reagent.
What distinguishes 2,4-Difluorobenzoyl Chloride from benzoyl chloride in terms of reactivity?
The two electron-withdrawing fluorine atoms at the 2- and 4-positions of 2,4-Difluorobenzoyl Chloride reduce the electron density on the carbonyl carbon more than in unsubstituted benzoyl chloride, generally making it a comparably reactive or slightly more electrophilic acylating agent. More importantly, the fluorine atoms are carried through into the product, providing fluorinated analogues with potentially distinct biological and physicochemical properties compared to non-fluorinated counterparts.
References
- March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley-Interscience: New York, 1992. (General reference for acyl chloride reactivity and Friedel-Crafts acylation.)
- Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012. (Reference for nucleophilic acyl substitution reactions.)
- Fluorine in Medicinal Chemistry and Chemical Biology; Ojima, I., Ed.; Wiley-Blackwell: Oxford, 2009. (General reference for fluorinated building blocks in drug discovery.)
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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