The synthesis of ibuprofen from 2-methylpropylbenzene also known as isobutylbenzene and carbon dioxide involves several steps. The key steps in the reaction are Friedel-Crafts acylation, hydrolysis, and Kolbe-Schmitt carboxylation. Here is a detailed mechanism of the synthesis:1. Friedel-Crafts Acylation:In the first step, 2-methylpropylbenzene reacts with acetyl chloride in the presence of a Lewis acid catalyst, such as aluminum chloride AlCl3 . The catalyst activates the acetyl chloride by forming a complex with it, making the carbonyl carbon more electrophilic. The 2-methylpropylbenzene then attacks the carbonyl carbon, resulting in the formation of a new carbon-carbon bond. The complex breaks apart, and the final product of this step is 2- 4-isobutylphenyl propanoyl chloride.2. Hydrolysis:The next step is the hydrolysis of the acyl chloride group in 2- 4-isobutylphenyl propanoyl chloride. This is achieved by treating the compound with water, which results in the replacement of the chloride group with a hydroxyl group. The product of this step is 2- 4-isobutylphenyl propanoic acid, also known as -methyl-4-isobutylphenylacetic acid.3. Kolbe-Schmitt Carboxylation:The final step in the synthesis of ibuprofen is the Kolbe-Schmitt carboxylation reaction. In this step, the -methyl-4-isobutylphenylacetic acid is treated with carbon dioxide and a strong base, such as sodium hydroxide NaOH , under high pressure and temperature. The base deprotonates the phenolic hydroxyl group, forming a phenoxide ion. The phenoxide ion then attacks the carbon dioxide, forming a new carbon-carbon bond. The resulting compound is the sodium salt of ibuprofen, which can be converted to the free acid form by treatment with a strong acid, such as hydrochloric acid HCl .In summary, the synthesis of ibuprofen from 2-methylpropylbenzene and carbon dioxide involves Friedel-Crafts acylation, hydrolysis, and Kolbe-Schmitt carboxylation. These steps result in the formation of the desired ibuprofen molecule.