How will you convert benzene into N, N – dimethylaniline.

Converting benzene into N,N-dimethylaniline involves a series of chemical reactions known as the Friedel-Crafts alkylation reaction. In this reaction, an aromatic ring, such as benzene, is alkylated by an alkyl halide to introduce alkyl groups onto the ring. In your case, you want to add two methyl groups (CH3) to the amino group (-NH2) of aniline to form N,N-dimethylaniline. Here's a step-by-step guide on how to do it:

Reagents and Conditions:

Aniline: You will start with aniline (C6H5NH2), which is a benzene ring attached to an amino group.

Methylating Agent: To introduce the methyl groups, you will need a methylating agent. Dimethyl sulfate (CH3SO4CH3) is commonly used for this purpose.

Lewis Acid Catalyst: A Lewis acid catalyst, typically aluminum chloride (AlCl3), is used to facilitate the Friedel-Crafts alkylation reaction.

Procedure:

Prepare the Reaction Mixture: In a dry and inert atmosphere, mix aniline and the methylating agent (dimethyl sulfate) in the presence of a Lewis acid catalyst (AlCl3). This mixture should be carefully handled in a fume hood due to the release of toxic gases.

Stir and Heat: Stir the reaction mixture while heating it gently. The Lewis acid catalyst helps in activating the benzene ring, making it more susceptible to nucleophilic attack.

Alkylation: The methyl group from dimethyl sulfate will attack the activated benzene ring, replacing one of the hydrogen atoms on the amino group. This process is called alkylation. The reaction will result in the formation of N-methylaniline.

N-Methylaniline

Repeat Alkylation: To form N,N-dimethylaniline, you need to repeat the alkylation process. Add another equivalent of dimethyl sulfate to the reaction mixture and continue heating and stirring.

Work-up: Once the reaction is complete, quench the reaction with water to hydrolyze any unreacted dimethyl sulfate and remove the Lewis acid catalyst. Afterward, extract the N,N-dimethylaniline from the aqueous phase using an organic solvent like diethyl ether or dichloromethane.

Purification: The crude N,N-dimethylaniline can be further purified by techniques such as distillation or recrystallization to obtain a higher purity product.

Please note that Friedel-Crafts alkylation reactions can be challenging to perform safely due to the use of toxic and reactive reagents. Proper safety precautions and appropriate laboratory equipment should be used when conducting such reactions. Additionally, the disposal of waste products and reagents must be handled according to local regulations and safety guidelines.