video tutorial Synthesis of mandelic acid from benzaldehyde

Mandelic acid synthesis from benzaldehyde (high-level)

• Form benzaldehyde bisulfite adduct by reacting benzaldehyde with sodium bisulfite in water; adduct precipitates.
• Perform a nucleophilic attack on the adduct with a cyanide salt (Na/K cyanide) to form mandelonitrile intermediate; extract and wash to purify.
• Hydrolyze mandelonitrile under acidic conditions (HCl), distill off toluene, and separate layers to yield mandelic acid in the aqueous phase.
• Isolate mandelic acid by crystallization, wash to remove impurities (including organic solvents), and dry thoroughly.
• Final product: off-white, odorless mandelic acid crystals; 8.94 g obtained from benzaldehyde (approximately 42% yield); product is racemic (50:50 mix of optical isomers).
• Notes: literature mentions recrystallization from benzene as an option, though solvent quantities may be large; purification improvements possible).