Preparation Of L-Phenylalanine Lab Report

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Lecturer Date Introduction Theoretical Background Procedure The procedure was segmented into two categories, the reaction set up and the crude product isolation. Reaction set up The magnetic stirrer was prepared through placing it in the fume cupboard. 1 mmol of L-Phenylalanine was placed and weighed in a 5 mL conical vial. After that, a spin vane was inserted into the vial while adding 0.75 mL of 1M H2SO4 solution. During the addition of the sulphuric acid, the solution was stirred at room temperature until the amino acid (L-Phe) completely dissolved. An ice bath was prepared and used for cooling the L-Phenylalanine solution at a temperature of 40C (a selected temperature lower than 50C). Once the solution was cooled, the first portion…show more content…
“Diazotization of L-phenylalanine results in the unstable aliphatic diazonium salt 2, which is believed to undergo a rapid, intramolecular SN2 reaction to give the highly strained R-lactone (3) (3)”. “In a second, slower, intermolecular SN2 reaction, 3 reacts with the solvent (water) to open the lactone and yield the final product, (S)-2-hydroxy-3-phenylpropanoic acid (4)”. “Because this process occurs with two SN2 reactions, the final product has a net retention of configuration”. “This reaction has the added advantage of being environmentally friendly: the reaction is run in aqueous solution, using a safe amino acid and generates no hazardous waste requiring disposal”. “This experiment illustrates some important chemical concepts, including: Water solubility dependence on the state of ionization of a compound, Stereospecificity of the SN2 reaction, Measurement of optical activity, Effect of diastereotopic protons in the 1 H NMR spectrum”. “The starting amino acid is highly soluble in the acidic solution of the reaction, the amphoteric nature of L-phenylalanine is apparent at the start of the reaction”. “The L-phenylalanine solution is cooled and then the aqueous NaNO2 solution is added with stirring”. “The reaction mixture begins to form tiny bubbles as the diazonium salt forms and nitrogen gas is liberated by the intramolecular reaction with the carboxylic acid”. “Reaction occurring as the Nitrogen bubbles form”. “This rapid intramolecular reaction reinforces the concepts

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