4-Fluorobenzimidamide hydroiodide
[CAS# 887623-88-3]

Identification

• Classification: Chemical reagent >> Organic reagent >> Amide
• Name: 4-Fluorobenzimidamide hydroiodide
• Synonyms: Benzenecarboximidamide, 4-fluoro-, hydriodide (1:1)
• Molecular Formula: C₇H₇FN₂.HI
• Molecular Weight: 266.05
• CAS Registry Number: 887623-88-3
• SMILES: C1=CC(=CC=C1F)C(=N)N.I

Discovery and Applications

4-Fluorobenzimidamide hydroiodide is a crystalline organic salt formed by the protonation of 4-fluorobenzimidamide with hydroiodic acid. The structure consists of a benzimidamide moiety substituted with a fluorine atom at the para position of the benzene ring, linked to an amidine functional group that is protonated to form the cation –C(=NH)NH₂⁺, with iodide as the counterion. The fluorine substituent influences the electronic properties of the aromatic ring, increasing electron-withdrawing character, while the hydroiodide salt form enhances the stability and solubility of the compound compared to the free base.

The discovery of fluorinated benzimidamides dates back to research on the structure–activity relationships of amidine-containing heterocycles. Substitution of a fluorine atom on the phenyl ring was systematically explored to modulate electronic density, receptor interactions, and metabolic stability. The hydroiodide salt form was developed to allow convenient handling, purification, and crystallization of the compound, as amidines are typically hygroscopic and prone to oxidation in their free base form.

Applications of 4-fluorobenzimidamide hydroiodide are primarily in pharmaceutical and synthetic chemistry. In medicinal chemistry, benzimidamide derivatives are known for their biological activity, including antiviral, antimicrobial, and enzyme inhibitory properties. Fluorination at the 4-position can enhance binding affinity to specific targets, increase resistance to enzymatic degradation, and improve pharmacokinetic profiles. Although the hydroiodide salt itself is mainly a laboratory form, it facilitates accurate dosing, solubility in aqueous and polar media, and ease of incorporation into reaction schemes for derivative synthesis.

In synthetic organic chemistry, 4-fluorobenzimidamide hydroiodide can serve as a precursor to substituted benzimidazole derivatives, heterocyclic frameworks widely used in drug discovery. The amidine functionality can undergo cyclization reactions to form benzimidazoles under appropriate conditions, and the fluorine atom provides a site for further functionalization or modulation of electronic properties. Additionally, the iodide counterion may participate in halide exchange reactions, offering versatility in the preparation of other salts or derivatives.

The combination of the aromatic fluorine substituent and the amidinium moiety also makes the compound relevant in supramolecular chemistry, where hydrogen bonding, electrostatic interactions, and halogen bonding can be exploited for the assembly of ordered structures. The crystalline hydroiodide form ensures well-defined solid-state packing, which can be important in studies of molecular recognition or in the design of functional materials.

Overall, 4-fluorobenzimidamide hydroiodide represents a stable, crystalline form of a fluorinated amidine derivative with applications in pharmaceutical research, heterocyclic synthesis, and supramolecular chemistry. Its discovery and development reflect the broader use of fluorine substitution to modify electronic properties and enhance stability, while the hydroiodide salt provides practical advantages in handling, solubility, and reactivity.

References

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