Alkyl Substituted Hydantoin-Based N-Halamine: Preparation, Characterization, and Structure–Antibacterial Efficacy Relationship

On the basis of the reaction of 5,5-dimethylhydantoin potassium salt with dibrominated alkane, a series of hydantoin derivatives in which two hydantoin rings are bridged by an alkyl chain with different length (C2, C6, C8, and C12) were synthesized. Upon chlorination, these compounds were transformed into hydantoin-based N-halamines. The structures of these samples were fully characterized with 1H NMR, FT-IR, UV/vis, thermal analyses, and iodometric titration. The antibacterial activity of these N-halamines was assessed with 4 × 109 CFU/mL of Gram-negative Escherichia coli under different chlorine concentrations and over different periods of contact time. It was found that the antibacterial properties and the releasing characteristics of the active chlorine of the hydantoin-based N-halamines changed obviously with increased alkyl chain length, and the factors influencing the antibacterial efficacy were discussed in terms of water solubility, steric effect, electron-donating effect, and action mechanism.