Double proton transfer in crystals of 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a] pyrimidine (hppH): 13C and 15N CPMAS NMR study of (hppH)2 |
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| Authors: | Martyn P Coles Majid S Khalaf Rosa M Claramunt M Angeles García Ibon Alkorta José Elguero |
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| Institution: | 1. Department of Chemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, UK BN1 9QJ, UK;2. Departamento de Química Orgánica y Bio‐Orgánica, Facultad de Ciencias, UNED, Senda del Rey, 9, E‐28040 Madrid, Spain;3. Instituto de Química Médica, CSIC, Juan de la Cierva, 3, E‐28006 Madrid, Spain |
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| Abstract: | In this paper, we report an example of intermolecular solid‐state proton transfer in the bicyclic guanidine, hppH. A combination of X‐ray crystallography, CPMAS NMR (13C and 15N) and theoretical calculations allows us to determine that a double proton transfer takes place in the (hppH)2 dimer with an activation energy of about 50 kJ mol?1. According to the B3LYP/6‐311++G(d,p) calculations, the double proton transfer occurs non‐symmetrically through a zwitterion. Copyright © 2009 John Wiley & Sons, Ltd. |
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| Keywords: | B3LYP/6‐311++G(d p) CPMAS NMR guanidines hydrogen bond proton transfer |
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