Question

SINCE Phenylalanine is reduced to Phenylalaninol in 16-18 hours under reflux with Sodium Borohydride and Sulfuric Acid in Dry Tetrahydrofuran.My question is to reduce 100gr of phenylalanine how much sodium borohydride and sulfuric acid is need?and in how many ml of dry thf must refluxed ? And after reflux i can remove the sodium borohydride with a filtration and and the thf/sulfuric acid/phenylalanine batch neutralised with NAOH and Phenylalaninol extracted with Toluen?

Answer 1

Answer on Question#75566 – Chemistry – General chemistry

Question:

SINCE Phenylalanine is reduced to Phenylalaninol in 16-18 hours under reflux with Sodium Borohydride and Sulfuric Acid in Dry Tetrahydrofuran. My question is to reduce 100gr of phenylalanine how much sodium borohydride and sulfuric acid is needed and in how many ml of dry thf must be refluxed? And after reflux, I can remove the sodium borohydride with a filtration and the thf/sulfuric acid/phenylalanine batch neutralised with NaOH and Phenylalaninol extracted with Toluene?

Answer:

You should use 2.5 eq NaBH₄:

$$m(NaBH_4) = 2.5 \times M(NaBH_4) \times \frac{m(Phe)}{M(Phe)} = 2.5 \times 37.83 \frac{g}{mol} \times \frac{100g}{165.19 \frac{g}{mol}} = 57.3g$$

You should use about 1000 mL THF.

Caution!

You should not use reflux. The reaction carries out under room temperature overnight. After you should carefully add about 100 mL methanol to destroy excess BH₃ (it formed during the reaction). The mixture have to be concentrated to 500 mL and you should add 5N NaOH (1L). For extraction you can use CH₂Cl₂.

Source:

https://www.sciencedirect.com/science/article/pii/S0040403900611334

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