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1H and 13C NMR studies of proton transfer in intramolecular hydrogen bonds in substituted 2-diethylaminomethylphenol N-oxides

✍ Scribed by Bogumił Brzezinski; Bogumił Brycki; Hanna Maciejewska-Urjasz; Georg Zundel

Publisher
John Wiley and Sons
Year
1993
Tongue
English
Weight
265 KB
Volume
31
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

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.

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