CHED 572 |
| 1,2,4-Triazolium salts have important applications as customizable ionic solvents. When the anion is varied, an unexpected dependence of the H5 resonance on the anion is observed in CDCl3, greater downfield shifts corresponding with increased anion basicity. It is proposed that this chemical shift results from hydrogen bonding between the anion and H5 in solution. H-C correlated NMR spectra were generated for 1-allyl-4-phenyl-1,2,4-triazolium bromide in CDCl3 at concentrations from 0.04M to 0.6M. As concentration increases, an upfield shift in H5 (12.6-12.2ppm) and a downfield shift in H3 (9.1-10ppm) is observed. A possible explanation for this shift is that as concentrations increase, hydrogen bonding to H3 becomes significant, attenuating the acidity of H5. X-ray crystallography of 1-allyl-4-phenyl-1,2,4-triazolium iodide and 1-benzyl-4-phenyl-1,2,4-triazolium chloride show the anion located near both H3 and H5 in hydrogen bonding positions. Further investigation includes more X-ray crystallography and computational models.
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Undergraduate Research Poster Session: Organic Chemistry
11:00 AM-1:00 PM, Monday, March 26, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Chemical Education |
