Cumene: Physicochemical properties, Oxidation Mechanism and Uses

Physicochemical properties

Cumene, also known as isopropylbenzene or 1-methylbenzene, is a flammable, volatile, colourless liquid with an odour similar to petrol. It is insoluble in water, but soluble in alcohol and many other organic solvents. Cumene is produced by the alkylation of benzene with propylene, a natural component of crude oil. It is commonly found in cigarette smoke and in plants in the natural environment. Its structure (Figure 1) and basic physical and chemical properties (Table 1) are:

Oxidation Mechanism

It is shown that [Bmim]OH can effectively accelerate the oxidation reaction rate of cumene and improve the conversion of cumene. The mechanism of the oxidation reaction of cumene catalysed by molecular oxygen activated [Bmim]OH has been reported. The nature of catalytic action and catalytic active sites of [Bmim]OH ionic liquids were also proposed.

The [Bmim]OH carbine-water structure plays an obvious catalytic role in the oxidation of cumene, which can induce the OO homolytic cleavage in cumyl hydroperoxide (CHP), leading to the formation of cumylhydroxy radicals (RO•) and carbene-OH radical-like intermediates, both of which are beneficial to the reactant with H of benzylic CH bond to accelerate the formation of cumyl radicals, involving in the propagation reaction that resulting in the formation of hydroperoxide and increasing the conversion of cumene. The overall reaction rate control step is the OO activation of CHP by [Bmim]OH carbine-water structure, which needs to overcome the energy barrier of 20.2 kcal/mol, lower than the auto-decomposition reaction energy barrier of CHP.

Uses of Cumene

Cumene is mainly used as an intermediate in the production of phenol and acetone. It is also used in the manufacture of styrene, a-methylstyrene and acetophenone. In addition, isopropylbenzene is used as a thinner for paints, lacquers and enamels. However, Cumene is irritating to the eyes and skin. Prolonged skin contact may result in dryness, desquamation and rashes. Exposure to vapour concentrations may result in central nervous system depression manifested by dizziness, slight incoordination and loss of consciousness.