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.