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15 N NMR study of azo‐hydrazone tautomerism of 15 N‐labelled azo dyestuffs
Author(s) -
Lyčka Antonín,
Šnobl Dobroslav,
Macháček Vladimír,
Večeřa Miroslav
Publication year - 1981
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270160106
Subject(s) - hydrazone , tautomer , chemistry , chemical shift , aniline , nitrogen , medicinal chemistry , organic chemistry
15 N chemical shifts of 3‐methyl‐1‐phenylpyrazole‐4,5‐dione 4‐phenylhydrazone (1), 4‐hydroxyazobenzene (2), 2‐hydroxy‐5‐ tert ‐butylazobenzene (3) and 1‐phenylazo‐2‐naphthol (4), monolabelled with 15 N at α‐(compounds prepared from 15 N‐aniline) and β‐positions (compounds prepared from Na 15 NO 2 ), have been measured and the temperature dependence of these chemical shifts followed between 240 and 360 K. For 4, representing a mixture of the azo and hydrazone forms, the hydrazone content has been calculated from the 15 N chemical shifts of both nitrogen atoms at various temperatures. The two calculations gave identical results.