The retrosynthesis pathway for the synthesis of ibuprofen from benzene involves several steps. Here is a possible retrosynthetic analysis:1. Ibuprofen: The target molecule is ibuprofen, which has an isobutyl group, a carboxylic acid group, and a 2-methylpropyl group attached to a benzene ring.2. Hydrolysis of the ester: The first retrosynthetic step is to convert the carboxylic acid group in ibuprofen to an ester, which can be achieved by hydrolysis. This would give us the corresponding ester of ibuprofen.3. Friedel-Crafts alkylation: The next step is to introduce the isobutyl and 2-methylpropyl groups onto the benzene ring. This can be done via Friedel-Crafts alkylation reactions. For this, we need to generate the corresponding alkyl halides isobutyl bromide and 2-bromo-2-methylpropane and use a Lewis acid catalyst, such as aluminum chloride AlCl3 .4. Nitration of benzene: Before performing the Friedel-Crafts alkylation, we need to introduce a directing group onto the benzene ring to control the regioselectivity of the alkylation reactions. This can be done by nitrating benzene to form nitrobenzene. Nitration is carried out using a mixture of concentrated nitric acid HNO3 and concentrated sulfuric acid H2SO4 .5. Reduction of nitrobenzene: The nitro group in nitrobenzene can be reduced to an amino group using various reducing agents, such as hydrogen gas H2 in the presence of a metal catalyst e.g., palladium on carbon or using iron Fe and hydrochloric acid HCl . This will give us aniline.6. Protection of the amino group: To prevent the amino group from reacting during the Friedel-Crafts alkylation, it needs to be protected. This can be done by converting the amino group to an amide using acetic anhydride Ac2O to form acetanilide.7. Friedel-Crafts alkylation of acetanilide: Now, the protected aniline acetanilide can undergo two Friedel-Crafts alkylation reactions with isobutyl bromide and 2-bromo-2-methylpropane to introduce the desired alkyl groups onto the benzene ring.8. Deprotection of the amide: After the alkylation reactions, the amide protecting group can be removed by hydrolyzing it back to the amino group using aqueous hydrochloric acid HCl .9. Diazotization and hydrolysis: Finally, the amino group can be converted to a carboxylic acid group by diazotization using sodium nitrite NaNO2 and hydrochloric acid HCl , followed by hydrolysis using a strong base like sodium hydroxide NaOH or potassium hydroxide KOH .This retrosynthetic analysis provides a possible pathway for the synthesis of ibuprofen from benzene. However, it is important to note that there may be other synthetic routes and strategies that could be employed to achieve the same goal.