To synthesize 2-phenylbutanoic acid from benzene, we can use the following retrosynthetic analysis:2-phenylbutanoic acid -> Friedel-Crafts alkylation -> benzyl bromide + 1,3-butadiene -> bromination -> benzeneHere's the step-by-step synthesis:1. Bromination of benzene: Reaction: Electrophilic Aromatic Substitution EAS Reagents: Br2, FeBr3 Lewis acid catalyst Conditions: Room temperature, anhydrous conditions Mechanism: - Formation of the electrophile: FeBr3 coordinates with Br2 to form a complex, which generates the electrophile Br+. - Electrophilic attack: The benzene ring attacks the Br+ electrophile, forming a carbocation intermediate. - Deprotonation: A base Br- deprotonates the carbocation intermediate, regenerating the aromatic ring and yielding bromobenzene.2. Conversion of bromobenzene to benzyl bromide: Reaction: Radical Chain Reaction Reagents: NBS N-bromosuccinimide , AIBN azobisisobutyronitrile, radical initiator , CCl4 solvent Conditions: Heating under reflux Mechanism: - Initiation: AIBN undergoes homolytic cleavage upon heating, generating two alkyl radicals. - Propagation step 1 : The alkyl radical abstracts a bromine atom from NBS, forming a new radical species and HBr. - Propagation step 2 : The bromine radical reacts with bromobenzene, abstracting a hydrogen atom from the benzylic position and forming benzyl bromide and a new bromine radical.3. Friedel-Crafts alkylation of benzyl bromide with 1,3-butadiene: Reaction: Friedel-Crafts Alkylation Reagents: 1,3-butadiene, AlCl3 Lewis acid catalyst Conditions: Room temperature, anhydrous conditions Mechanism: - Formation of the electrophile: AlCl3 coordinates with the benzyl bromide, generating a carbocation at the benzylic position. - Electrophilic attack: The 1,3-butadiene attacks the carbocation, forming a new carbocation intermediate. - Deprotonation: A chloride ion from AlCl4- deprotonates the carbocation intermediate, yielding 1-phenylbut-1-ene.4. Oxidation of 1-phenylbut-1-ene to 2-phenylbutanoic acid: Reaction: Oxidation Reagents: KMnO4, H2O solvent , H2SO4 acidic conditions Conditions: Heating under reflux Mechanism: - Formation of the diol: The alkene reacts with the permanganate ion MnO4- under acidic conditions, forming a cyclic intermediate which then hydrolyzes to form a vicinal diol. - Oxidative cleavage: The diol undergoes oxidative cleavage by another equivalent of permanganate ion, yielding 2-phenylbutanoic acid and a carboxylic acid byproduct formic acid .The final product, 2-phenylbutanoic acid, is obtained through this multi-step synthesis starting from benzene.