✍ Scribed by M. Rospenk; L. Sobczyk
No coin nor oath required. For personal study only.
The 'H chemical shifts of the active bridge protons and their temperature dependences were measured in various solvents for a number of ortho-Mannich bases containing proton-donor (OH) and proton-acceptor (N) centres of varying strength. It was found that a maximum on the plot of 6 , versus ApK, occurs, similar to that in intermolecular hydrogen-bonded systems, although the shape of the plot is different. The maximum is located in the critical (inversion) region where the proton transfer equilibrium takes place. The contribution of the proton transfer form increases substantially on cooling, so that one observes a dramatic temperature effect on the chemical shift for some derivatives. The line width of the bridge protons shows a sharp narrowing in the critical region, which can be interpreted as being due to the fast jumping of protons between the donor and acceptor atoms.
📜 SIMILAR VOLUMES
## 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 th
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