Benzene to Phenol Reaction Mechanism Video Lecture | Chemical Technology - Chemical Engineering

Ans. The reaction mechanism for the conversion of benzene to phenol involves the following steps: 1. Activation of benzene: Benzene is activated by the reaction with a strong Lewis acid catalyst, such as aluminum chloride (AlCl3), which forms a complex with benzene. 2. Electrophilic substitution: The activated benzene reacts with nitric acid (HNO3) to form nitrobenzene. This reaction is called electrophilic substitution, where the nitro group (-NO2) replaces one of the hydrogen atoms on the benzene ring. 3. Reduction: Nitrobenzene is then reduced by hydrogen gas (H2) in the presence of a metal catalyst, such as palladium (Pd) or nickel (Ni), to form aniline. 4. Oxidation: Aniline is oxidized using an oxidizing agent, such as air or sodium dichromate (Na2Cr2O7), to form nitrosobenzene. 5. Rearrangement: Nitrosobenzene undergoes rearrangement in the presence of water and sulfuric acid (H2SO4) to form phenol.

Ans. A catalyst, such as aluminum chloride (AlCl3), is used in the benzene to phenol reaction to activate the benzene molecule. The catalyst acts as a Lewis acid, forming a complex with benzene, which increases its reactivity. This activation allows benzene to react with other reagents, such as nitric acid and hydrogen gas, to undergo the necessary chemical transformations and produce phenol. The catalyst speeds up the reaction by lowering the activation energy, making the reaction more favorable and efficient.

Ans. Nitric acid (HNO3) plays a crucial role in the conversion of benzene to phenol. It reacts with the activated benzene, formed in the presence of a catalyst, to form nitrobenzene through electrophilic substitution. Electrophilic substitution involves the replacement of one of the hydrogen atoms on the benzene ring with a nitro group (-NO2). Nitrobenzene serves as an intermediate compound in the reaction, undergoing further transformations to eventually produce phenol. Therefore, nitric acid acts as a reagent that introduces the necessary functional group to the benzene molecule, enabling the subsequent chemical conversions.

Ans. The reduction step in the benzene to phenol reaction is necessary to convert nitrobenzene, formed in the previous step, into aniline. Nitrobenzene cannot be directly converted to phenol, so it needs to be reduced to an intermediate compound, aniline, before further transformations can occur. This reduction is typically carried out using hydrogen gas (H2) in the presence of a metal catalyst, such as palladium (Pd) or nickel (Ni). Aniline then undergoes subsequent oxidation and rearrangement steps to form phenol. Therefore, the reduction step is essential to provide the necessary starting material for the formation of phenol.

Ans. The oxidation step in the benzene to phenol reaction typically requires an oxidizing agent, such as air or sodium dichromate (Na2Cr2O7). Aniline, the product of the reduction step, is oxidized to form nitrosobenzene. The oxidation reaction can be carried out in the presence of a suitable catalyst or under mild conditions. The rearrangement step, which converts nitrosobenzene to phenol, requires the presence of water and sulfuric acid (H2SO4). The reaction takes place under acidic conditions, with water and sulfuric acid facilitating the rearrangement of the nitrosobenzene molecule. The exact conditions and reaction parameters may vary depending on the specific reaction setup and desired yield of phenol.