When benzene is heated in air with V₂O₅ at 450°C, it undergoes ?

When benzene is heated in the presence of air and vanadium pentoxide (V₂O₅) at around 450°C, it undergoes an oxidation reaction. Under these conditions, benzene reacts with oxygen, and V₂O₅ acts as an oxidation catalyst, converting benzene into maleic anhydride (C₄H₂O₃) — an important industrial intermediate.

The balanced chemical equation for the reaction is:

C6H6+92O2→V2O5,450°CC4H2O3+2CO2+2H2OC_6H_6 + \frac{9}{2}O_2 \xrightarrow{V_2O_5, 450°C} C_4H_2O_3 + 2CO_2 + 2H_2OC6H6+29O2V2O5,450°CC4H2O3+2CO2+2H2O

This reaction is a clear example of controlled catalytic oxidation. Instead of complete combustion (which would produce only CO₂ and H₂O), the presence of V₂O₅ allows partial oxidation to a specific organic product. Maleic anhydride formed in this reaction is widely used in the production of alkyd resins, plasticizers, copolymers, and coatings.

The oxidation process involves the breaking of the aromatic ring in benzene and the introduction of oxygen atoms. The catalyst V₂O₅ helps lower the activation energy, enabling oxidation at a lower temperature while maintaining selectivity for the desired product.

It is important to note that benzene, being a highly stable aromatic compound due to its delocalized π-electrons, resists oxidation under mild conditions. Only under high-temperature catalytic conditions does oxidation occur efficiently.

Therefore, when benzene is heated in air with vanadium pentoxide at 450°C, the reaction is not a substitution, addition, or elimination reaction but a catalytic oxidation.

This reaction serves as a classic example in organic industrial chemistry, demonstrating how catalysts such as V₂O₅ can transform stable aromatic compounds into valuable chemical intermediates.