Electron-Withdrawing Trifluoromethyl Groups in Combination with Hydrogen Bonds in Polyols: Brønsted Acids, Hydrogen-Bond Catalysts, and Anion Receptors

Electron-withdrawing trifluoromethyl groups were characterized in combination with hydrogen-bond interactions in three polyols (i.e., CF₃CH­(OH)­CH₂CH­(OH)­CF₃, 1; (CF₃)₂C­(OH)­C­(OH)­(CF₃)₂, 2; ((CF₃)₂C­(OH)­CH₂)₂CHOH, 3) by pK_a measurements in DMSO and H₂O, negative ion photoelectron spectroscopy and binding constant determinations with Cl^–. Their catalytic behavior in several reactions were also examined and compared to a Brønsted acid (HOAc) and a commonly employed thiourea ((3,5-(CF₃)₂C₆H₃NH)₂CS). The combination of inductive stabilization and hydrogen bonds was found to afford potent acids which are effective catalysts. It also appears that hydrogen bonds can transmit the inductive effect over distance even in an aqueous environment, and this has far reaching implications.