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

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journal contribution
posted on 2013-06-26, 00:00 authored by Alireza Shokri, Xue-Bin Wang, Steven R. Kass
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 pKa 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.