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The influence of the 1-adamantyl group on the structure and the proton transfer dynamics of N-unsubstituted pyrazoles has been determined. Four compounds have been labelled with 15 N and studied by variable temperature 15 N CP MAS NMR spectroscopy: 3(5)-(1-adamantyl)pyrazole 2, 4-(1-adamantyl)pyrazole 3, 3,5-dimethyl-4-(1-adamantyl)pyrazole 4 and 3,5-di(1-adamantyl)pyrazole 5. Compound 2 (a 1∶1 mixture of both tautomers) is a long chain of hydrogen bonded molecules (‘catemer’) and as in most catemers there is no proton transfer since it would imply an ‘infinite’ number of proton jumps. Compound 3, although also a ‘catemer’, is possibly an exception to this rule, in that it seems to show proton transfer. In the solid state, compounds 4 and 5 should be cyclic hydrogen-bonded structures, dimers or trimers, but the activation energies for proton transfer, about 39 kJ mol -1 , are quite low compared …