Hydroxyl groups alkylation with acidic functional residues

Phenolic resins are well known for their contribution in improving hardness, gloss, and water and chemical resistance in oleoresinous varnishes. Those based on p-alkyl-substituted phenols and with heat-reactive methylol groups have also been incorporated into alkyd resins. The reaction has not been well smdied. Presumably, the methylol group would react with the unsaturation functionality on the fatty acid chain to form the chroman stmcture, similar to what is believed to have occurred in the varnish. Etherification between the methylol group and free hydroxyl of the alkyd resin, catalyzed by the residual acidity in the resin, would be another possible reaction. 

---