Document Detail


Tautomerism and possible polymorphism in solid hydroxypyridines and pyridones studied by 14N NQR.
MedLine Citation:
PMID:  23347232     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
14N nuclear quadrupole resonance frequencies have been measured in solid 2-pyridone, 3-hydroxypyridine and 4-pyridone by 1H-14N nuclear quadrupole double resonance. Two slightly nonequivalent nitrogen positions are observed in solid 3-hydroxypyridine, whereas only one nitrogen position has been observed in 2-pyridone and 4-pyridone within the experimental resolution. Rather low 14N quadrupole coupling constants in pyridones are the consequence of the delocalization of the nitrogen lone pair electrons in the aromatic rings. Two different compounds have been obtained by crystallization of 4-pyridone from ethanol in a normal and in a dry atmosphere. The compound obtained in the dry atmosphere is identical to the commercial sample. The compound obtained in the normal atmosphere cannot be converted to the commercial polymorph by melting. It is thus not a polymorph of anhydrous 4-pyridone. The temperature coefficient of the 14N quadrupole coupling constant is negative in 3-hydroxypyridine and positive in 2- and 4-pyridone. So in 3-hydroxypyridine molecular librations dominate the temperature variation of the quadrupole coupling constant whereas in in 2- and 4-pyridone the chang.
Authors:
Janez Seliger; Veselko Zagar
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-24
Journal Detail:
Title:  The journal of physical chemistry. A     Volume:  -     ISSN:  1520-5215     ISO Abbreviation:  J Phys Chem A     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9890903     Medline TA:  J Phys Chem A     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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