What products are formed when phenol undergoes oxidation with chromic acid, and how does the oxidation of phenols in the presence of air typically progress?

When phenol undergoes oxidation with chromic acid (H₂CrO₄), the main product is benzoquinone (C₆H₄O₂). The oxidation typically involves the conversion of phenol to benzoquinone, which is a dicarbonyl compound. In the presence of air, the oxidation of phenols can further progress to form more highly oxidized products, such as polymeric quinones. These reactions involve the incorporation of molecular oxygen, leading to the formation of reactive intermediates and the generation of more complex oxidation products. The exact pathway and products depend on reaction conditions and the specific phenolic substrate involved.