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1 H and 13 C NMR studies of proton transfer in intramolecular hydrogen bonds in substituted 2‐diethylaminomethylphenol N ‐oxides
Author(s) -
Brzezinski Bogumił,
Brycki Bogumił,
MaciejewskaUrjasz Hanna,
Zundel Georg
Publication year - 1993
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.1260310707
Subject(s) - chemistry , intramolecular force , proton , hydrogen bond , proton nmr , nuclear magnetic resonance spectroscopy , computational chemistry , crystallography , stereochemistry , molecule , organic chemistry , nuclear physics , physics
Eleven substituted 2‐diethylaminomethylphenol N ‐oxides were studied in CDCl 3 solutions by 1 H and 13 C NMR spectroscopy. The 1 H chemical shifts of the intramolecular hydrogen‐bonded proton and the Δ 14 values obtained from the 13 C signals were considered as a function of the p K a values of the parent phenols. The 1 H chemical shift of the hydrogen‐bonded proton shows a maximum at p K a ≈ 7. This result agrees well with the turning point of the curve if Δ 14 is plotted as a function of the p K a of the parent phenols. All these results agree well with recently obtained Fourier transform IR results. With the system with the strongest hydrogen bond (p K a ≈ 7) a broad, flat, single‐minimum proton potential or a double‐minimum proton potential with a small barrier is present. With this system the deshielding of the proton in the intramolecular hydrogen bond is strongest.