Abstract
The ph dependence of an alternating linewidth effect observed in the electron resonance spectrum of the monoprotonated trans-biacetyl semidione radical has been investigated; it is interpreted in terms of an acid-catalysed tautomerism of the radical. A simple Bloch-equation treatment shows that this process is first order with respect to hydrogen ions and has a rate constant at 23°c of 4·53 × 109 l. mol-1 sec-1.