Deuterium isotope effect in proton magnetic resonance spectra of 3‐hydroxy‐2‐butanone: (Short communication)

Abstract

As part of a study on the oxidation of 3-hydroxy-2-butanone, "acetoin", it became necessary to know the rate of its enolization in acidic aqueous solution. This rate was estimated by following the proton magnetic resonance spectrum when acetoin was dissolved in 2N DzSOd-DzO; see Table I. Except for the hydroxyl hydrogen, position c is deuterated faster than position a, while position b is deuterated at the lowest rate.In a 100 MHz spectrum of acetoin the coupling constant JH-C-C-H = 7.2 f 0.1 Hz and the shift between the quartet signal of a and the doublet signal of b amounts to 6 = 304 Hz. Thus, J/6 = 0.024, with a near ideal A 3X spectrum.Because of partial deuteration in position a, the original doublet of hydrogen b in the proton magnetic resonance spectrum of acetoin is accompanied by a somewhat broadened singlet. This singlet does not coi'ncide with the centre of the doublet, but is shifted over 0.8 f 0.1 Hz to higher field. 1 J. Lubach, W. Drenth and G. J. M. van der Kerk, to be published.

Determination of Substrate and Product Concentrations in Lactic Acid Bacterial Fermentations by Proton NMR Using the ERETIC Method

“…Another choice could be D 2 O. However, it has previously been shown that acetoin or diacetyl exchanges deuterium with D 2 O . Similarly, due to the hydration/dehydration described above, diacetyl will exchange with D 2 O.…”