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13C CP-MAS study of the polymorphs of naphthazarin and of some methyl derivatives

✍ Scribed by Alejandro Olivieri; Iain C. Paul; David Y. Curtin

Publisher
John Wiley and Sons
Year
1990
Tongue
English
Weight
498 KB
Volume
28
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

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.

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