The preparation of phenylalanine from benzyl chloride and ammonia involves a two-step process: nucleophilic substitution followed by reductive amination.1. Nucleophilic substitution: In the first step, benzyl chloride C6H5CH2Cl reacts with ammonia NH3 in a nucleophilic substitution reaction S_N2 mechanism . The lone pair of electrons on the nitrogen atom of ammonia attacks the electrophilic carbon atom of benzyl chloride, displacing the chloride ion Cl- and forming a benzylamine intermediate C6H5CH2NH2 .2. Reductive amination: In the second step, benzylamine reacts with an aldehyde or ketone, such as pyruvaldehyde CH3COCOH , in the presence of a reducing agent like sodium cyanoborohydride NaBH3CN . The nitrogen atom of benzylamine attacks the carbonyl carbon of pyruvaldehyde, forming an imine intermediate. The imine is then reduced by the reducing agent to form phenylalanine C6H5CH2CH NH2 COOH .To optimize the reaction and increase the yield of phenylalanine, several factors can be considered:1. Temperature: The nucleophilic substitution step is exothermic, so maintaining a low temperature 0-5C can help control the reaction rate and minimize side reactions.2. Solvent: Using a polar, aprotic solvent like dimethyl sulfoxide DMSO or dimethylformamide DMF can help stabilize the transition state and promote the S_N2 reaction.3. Excess ammonia: Using an excess of ammonia can help drive the nucleophilic substitution reaction to completion and minimize the formation of by-products.4. Reducing agent: Choosing an appropriate reducing agent, such as sodium cyanoborohydride, can selectively reduce the imine intermediate without affecting other functional groups in the molecule.5. Reaction time: Allowing sufficient time for the reductive amination step to reach completion can help maximize the yield of phenylalanine.6. Purification: Efficient purification techniques, such as column chromatography or crystallization, can help separate phenylalanine from any remaining starting materials or side products.