Premium
13 C CP‐MAS study of the polymorphs of naphthazarin and of some methyl derivatives
Author(s) -
Olivieri Alejandro,
Paul Iain C.,
Curtin David Y.
Publication year - 1990
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260280206
Subject(s) - chemistry , tautomer , intramolecular force , hydrogen bond , ring (chemistry) , nmr spectra database , spectral line , solid state , proton nmr , nuclear magnetic resonance spectroscopy , proton , crystallography , stereochemistry , medicinal chemistry , molecule , organic chemistry , physics , quantum mechanics , astronomy
The high‐resolution 13 C solid‐state NMR spectra of naphthazarin polymorphs and some of its derivatives having methyl substituents are discussed. Differences observed between the spectra of the A and B forms and that of the C modification of naphthazarin are explained by invoking hydrogen‐bonding effects. The 2‐methyl and 2,3‐dimethyl derivatives show spectra consistent with their x‐ray‐determined structure as being mainly composed of the tautomer bearing the substituents on the quinonoid ring. The 2,7‐dimethyl‐substituted compound undergoes a fast intramolecular proton migration at room temperature between tautomers present in nearly equal amounts.