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Isotopic exchange in heterocyclic quaternary salts. II. (1) Hydrogen‐deuterium exchange ln active c‐methyl groups
Author(s) -
Bologa Margareta,
Barabás A.,
Dénes Viorica I.,
Chiraleu F.
Publication year - 1977
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580130102
Subject(s) - chemistry , hydrogen–deuterium exchange , deuterium , ammonium , medicinal chemistry , chemical shift , hydrogen , inorganic chemistry , stereochemistry , organic chemistry , physics , quantum mechanics
The non‐catalysed H‐D exchange in heterocyclic quaternary ammonium salts (1–3) was studied by 1 H‐nmr. Exchange occurs only at the C‐CH 3 group, at a rate decreasing in the order X = C(CH 3 ) 2 , Se, CH=CH, S, NCH 3 . In substituted benzothiazolium salts the exchange rates decrease in the series Y = NO 2 , Cl, H, OCH 3 . Chemical shifts (δ) of C‐CH 3 and N‐CH 3 groups decrease in the same sequence. Both exchange rate constants and chemical shifts can be related ta Hammett σp‐ values of the Y substituents. The mechanism p of the exchange reaction is briefly discussed.