A nuclear magnetic resonance study of diethylamine hydrogen bonding

The concentration dependence of the chemical shift of the diethylamine NH proton was studied both in the hydrogen-bonding solvent acetonitrile and in the nonhydrogen-bonding solvent cyclohexane. In the cyclohexane solutions the N-H-N bonds in pure diethylamine break upon dilution and the resonance position of the N-H peak changes toward higher magnetic fields, whereas in acetonitrile solutions the N-H resonance changes systematically toward lower fields as the concentration of amine decreases. Thus, the N-H group of diethylamine forms a stronger hydrogen bond with acetonitrile than with itself. Rapid exchange of the diethylamine N-H proton appears to result from trace amounts of water present in acetonitrile and cyclohexane.