Spectroscopic and theoretical investigation of capillary-induced keto-enol tautomerism of phenacyl benzoylpyridinium-type photoinitiators

Phenacyl benzoylpyridinium (PBP) salts are effective photoinitiatiors for cationic polymerization. In this study, it is shown that PBP salts are stable in their keto forms, and undergo a reversible keto-enol tautomerization reaction when a capillary action is applied. Spectroscopic and theoretical methods are used to explain the existence of the enol forms in the capillary tube.