Chemical Structure and Key Properties

2-Chloro-3-fluoropyridine-4-carboxylic acid (molecular formula C₆H₃ClFNO₂, MW 175.54 g/mol) is a pyridine-4-carboxylic acid derivative in which the ring nitrogen is at position 1, a chlorine atom occupies position 2, and a fluorine atom occupies position 3. This arrangement of two distinct halogens flanking the carboxylic acid at C-4 creates a highly electron-deficient aromatic ring.

The electron-withdrawing effects of both the ring nitrogen and the two halogen substituents reduce electron density across the pyridine ring, lowering the pK_a of the carboxylic acid relative to unsubstituted pyridine-4-carboxylic acid (isonicotinic acid) and increasing the ring's susceptibility to nucleophilic aromatic substitution (S_NAr). Researchers should note that the C–F bond at C-3 is particularly activated toward S_NAr due to the combined ortho/para electron-withdrawing influence of the ring nitrogen and the adjacent chlorine.

The compound is expected to present as a solid at room temperature. Precise melting point, solubility, and other physicochemical data should be verified against the certificate of analysis supplied with each batch (SKU C139111).

Synthetic Applications and Reactivity

The dual electrophilic sites of 2-Chloro-3-fluoropyridine-4-carboxylic acid make it a multifunctional synthetic building block. The three principal modes of reactivity exploited in laboratory synthesis are:

• Nucleophilic Aromatic Substitution (S_NAr): The C-3 fluorine, activated by flanking electron-withdrawing groups, is preferentially displaced by oxygen, nitrogen, or sulfur nucleophiles under mild conditions. The C-2 chlorine may also participate under more forcing conditions or with specific nucleophiles, enabling sequential, selective functionalization.
• Transition-Metal-Catalyzed Cross-Coupling: Both the C–Cl and C–F bonds serve as electrophilic partners in palladium- or nickel-catalyzed reactions (e.g., Suzuki–Miyaura, Negishi, or Buchwald–Hartwig couplings). Selective coupling at C-2 chlorine is generally achievable under standard palladium catalysis, leaving the C–F bond intact for subsequent transformations.
• Carboxylic Acid Transformations: The –COOH group can be converted to acid chlorides, esters, amides, or reduced to the corresponding aldehyde or alcohol, providing further diversification of the molecular scaffold. Amide bond formation with amines generates pyridinecarboxamide motifs frequently encountered in kinase inhibitor pharmacophores.

These complementary reactivities allow medicinal chemists to use this compound as a versatile core for library synthesis, accessing structurally diverse analogs from a single starting material.

Safe Handling and Storage Guidelines

Although specific GHS hazard classifications for 2-Chloro-3-fluoropyridine-4-carboxylic acid (C139111) should be confirmed from the product Safety Data Sheet (SDS) before use, general precautions applicable to halogenated heteroaromatic carboxylic acids include the following:

• Personal Protective Equipment (PPE): Wear chemical-splash goggles, a laboratory coat, and nitrile gloves. Where dust generation is possible during weighing, use a fitted particulate respirator or work inside a fume hood.
• Ventilation: All handling, weighing, and reaction setup should be performed inside a well-ventilated fume hood to minimize inhalation exposure.
• Storage: Store in a tightly sealed container in a cool, dry location away from strong bases, oxidizers, and moisture. Refrigerated storage (2–8 °C) is typically recommended for long-term stability of halogenated pyridine derivatives; consult the product label for batch-specific conditions.
• Disposal: Dispose of waste material and contaminated solvents in accordance with local, institutional, and national regulations for halogenated organic waste.
• First Aid: In the event of skin or eye contact, flush immediately with copious water for at least 15 minutes and seek medical advice. Refer to the SDS for complete emergency response procedures.

Researchers are strongly advised to obtain and review the current SDS for SKU C139111 from Aladdin Scientific prior to first use.

Analytical Characterization and Quality Considerations

When receiving a batch of 2-Chloro-3-fluoropyridine-4-carboxylic acid (SKU C139111), researchers should verify compound identity and purity using the following standard analytical techniques before committing the material to key synthetic steps:

• ¹H and ¹⁹F NMR Spectroscopy: Proton NMR (typically acquired in DMSO-d₆ or CDCl₃) should show characteristic aromatic signals consistent with a 1,2,3-trisubstituted pyridine. The broad exchangeable carboxylic acid proton typically appears downfield (>10 ppm). ¹⁹F NMR provides a direct, sensitive confirmation of the fluorine substituent chemical shift.
• HPLC Purity Analysis: Reverse-phase HPLC with UV detection at 254 nm is the standard method for quantifying chemical purity. A purity specification of ≥97% (or as stated on the CoA) is typical for research-grade material.
• Mass Spectrometry: ESI-MS or APCI-MS should confirm the molecular ion consistent with the molecular formula C₆H₃ClFNO₂ (MW 175.54). The isotopic pattern of chlorine (approximately 3:1 M:M+2 ratio) serves as an additional confirmatory marker.
• Melting Point: Comparison of the observed melting point against the certificate of analysis value provides a rapid purity check. Significant depression of the melting point may indicate the presence of impurities.

All purity and identity data should be cross-referenced with the certificate of analysis (CoA) provided by Aladdin Scientific for each specific lot number.