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Isotopic Polymorphism in Pyridine


  • Dedicated to Dr. Frank Allen on the occasion of his retirement as Executive Director of the Cambridge Crystallographic Data Centre. We thank Prof. G. R. Desiraju for suggesting crystallization of [D5]pyridine and STFC for provision of neutron beam time and a studentship for S.C. R.B. gratefully acknowledges the support of the DFG FOR 618.


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Not so simple: It is normally assumed that deuteration has only a minor effect on the stabilities of crystal structures. This assumption is wrong for pyridine. A low-temperature polymorph exists for [D5]pyridine, but not for [H5]pyridine, which adds a further twist to the already unusual structural chemistry of one of the simplest and most familiar laboratory chemicals.