I'm confused about the mechanism for the isomerization of the external alkene eugenol to the internal alkene isoeugenol. I've added an image below of their structures.
The reaction is usually carried out using a strong base (sodium or potassium hydroxide) in a polyol solvent (typically glycerol or ethylene glycol).
I have no idea why this might happen, especially given that there's no carbonyls with acidic alpha carbons in the molecule. Maybe eugenol phenoxide is responsible?