Honors Theses

Date of Award

5-2026

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Chemistry

Faculty Mentor

James Davis, Jr. Ph.D.

Advisor(s)

Terrence J. Ravine, Ph.D. and Richard O'Brien, Ph.D.

Abstract

Quaternary ammonium compounds (QACs) are widely used in disinfectants due to their ability to inhibit the growth of and eliminate microbes. The potency, broad-spectrum activity, and low cost of QACs have made them a cornerstone of modem hygiene. In recent years, QACs have garnered many health and safety concerns due to their overuse and subsequent accumulation in the environment. The increased use of QACs has further led to an increase in antimicrobial-resistant bacteria, making the synthesis of novel antibacterial compounds vital to combat this growing threat. Recent advances in boronium salts offer a unique alternative to address these adverse effects. Previous work has shown that boronium salts containing C12, C14, and C16 alkyl chains exhibit antimicrobial activity comparable to QACs while displaying reduced cytotoxicity. However, these salts are sparingly soluble in aqueous solutions.

One possible solution is to utilize recently discovered boronium salts bonded to an 0- donor such as urea. Urea contains two nitrogens from which hydrogen bonding can occur, allowing for increased water solubility. The capacity to hydrogen bond may exhibit more favorable interactions with the hydrophilic portion of a microbe's phospholipid bilayer and increase microbial inhibition. To study these hypotheses, urea-based boronium salts were synthesized in which the number and positions of hydrogens on the urea ligand was varied to study the effects of hydrogen bonding. Each urea ligand was studied with alkyl chains of lengths C14, C16, and C1s to determine the optimal alkyl chain length. Using minimum inhibitory concentration assays we found that the C14 exhibited similar potency to the commercial Pestanal standard while the C16 and C1s often lacked similar potency. Varying the position and number of hydrogens did not have an effect on the potency of the antimicrobials. Ultimately, the urea-based boronium salts do show promise as an alternative to current antimicrobial but require further testing to determine the full extent of their utility.

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