125 Competition Between Intramolecular and Intermolecular Hydrogen Bonding in Catechol Using Various Pi Electron Bases

Wednesday, November 4, 2009: 10:20 AM
Longhorn (Camino Real Hotel)
Adriana Pavia , Department of Chemistry, St. Edward's Univeristy, Austin, TX
J.D. Lewis , Department of Chemistry, St. Edward's University, Austin, TX
Our recent infrared studies of the competition between intramolecular and intermolecular hydrogen bonding in catechol have used pi electron hydrogen bonding bases such as toluene, mesitylene, and p-xylene. The solvent for our studies is cyclohexane since this solvent produces relatively sharp OH stretching bands for dilute solutions of catechol. The infrared spectrum of 0.003M catechol in cyclohexane exhibits two OH-stretching bands at 3622 cm-1 and 3576 cm-1, one assigned to a free OH conformation (free band) and the other to a OH conformation with intramolecular hydrogen bonding (intra HB band). As the hydrogen bonding base is added to the solution at increasing concentrations a lower frequency band appears assigned to OH conformations with intermolecular hydrogen bonding. A second intra HB band, slightly shifted to lower frequency, also appears as the concentration of the external base is increased. This work considers how these features vary with increasing base concentration and differing pi electron sources used as the external base.
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