Rapid Proton Exchange Research Articles

Rapid proton exchange of the free radical ·CH2OH as studied by E.S.R.

From the pH-dependence of the hydroxy proton splitting in the electron spin resonance spectra of the free radical ·CH2OH in acidified aqueous solutions a rapid exchange of the hydroxy protons is detected. This exchange is explained by the reaction ·CH2OH+H3O+⇆·CH2OH2 ++H2O with a rate constant k=1.76×108 l.mol-1 sec-1 at 17°c.

Transient nuclear magnetic resonance signals for liquids with exchanging nuclei

Experimental results are given for both the steady-state proton magnetic resonance line shape and for the echo amplitude modulation pattern for liquid methyl alcohol over a temperature range which includes the collapse of the J multiplet due to increasingly rapid hydroxyl proton exchange. A theory is given for the modulation of the echo amplitude in the presence of exchange by a generalization of Anderson and Weiss's method [9] and also by use of McConnell's equations [10]. An approximate theory is also given which gives considerable insight into the physical meaning of the more complex exact solutions. The value of the approximate method is also illustrated by applying it to the analysis of the collapse of the complex methyl multiplet in NN dimethyl formamide. It is shown that, generally speaking, the echo amplitude modulation measurement, while giving similar results as for the steady-state measurements, have certain advantages both in the determination of coupling constants and exchange correlation tim...

NUCLEAR MAGNETIC RESONANCE STUDY OF ION-EXCHANGE RESINS. I. HYDRATED DOWEX-50 RESINS

The proton magnetic resonance spectra for hydrated ion-exchange resin samples were measured. The effect on the chemical shift and line width was observed as a function of resin phase hydration, resin cross linkage, and temperature for Dowex-50. The effects are interpreted in terms of changes in water structure and rapid proton exchange in the resin phase. (auth)