In this experiment, if a student obtains an amine with [alpha ]20 30 = -3 5 .3 d

Question

In this experiment, if a student obtains an amine with [alpha ]20 30 = -3 5 .3 degree , then: What is the optical purity of the amine? Calculate the %(S) and %(R) enantiomers of the amine in the sample. How could you isolate the R-(+)-alpha phenylethylamine from the mother liquor that remained after you crystallized and filtered off the S-(-)-alpha-phenylethylamine? The formation of a white solid is often observed after alpha-phenylethylamine comes into contact with carbon dioxide in the atmosphere. What is that white compound? Give an equation that shows its formation. If the boiling point of the pure of (S)-(-)-alpha-phenylethylamine is 1 8 6 -1 8 8 degree C, what is the bp of its enantiomer? What optical rotation would be observed if 3 .7 2 g of the (S)-amine were mixed with 3 .7 2 g of the (R)-amine? Propose a method for how you would resolve (plusminus)-2-chloropropanoic acid [(plusminus)-RCOOH] using (-)-amphetamine [(-)-RHN2 as the resolving agent. Do the same for Calculate the specific rotation of a substance that is dissolved in a solvent (0.35 g/mL) and that has an observed rotation of - 2 3 degree as determined with a 0.5 dm cell. Calculate the observed rotation of a substance that is dissolved in solution at 2 .5 g/mL and is 7 5% optically pure. Assume a 1.0 dm cell is used. The specific rotation of the optically pure substance is + 40 degree.

Explanation / Answer

% Optical purity of sample = 100 * (specific rotation of sample) / (specific rotation of a pure enantiomer)

1.a).

for this part we need to know the specific optical rotation of the amine

this must be given while you performed th experiment

assuming it to be -40 degre

we get optical purity= 35.3/40=88.25%

b).% s is 5.87%

and R is 94.127%

2).(-)-?-Phenylethylamine;Add 31.25 g of D-tartaric acid (0.208 mole) to 450 ml of methanol in a one-liter Erlenmeyer flask, and heat the mixture almost to boiling. To the hot solution add cautiously 25 g of D,L-?-phenylethylamine (26.6 ml; 0.206 mole),-1too rapid addition will cause the mixture to boil over. Since crystallization occurs slowly, the solution must be allowed to stand at room temperature for about 24 hours. The (-)-amine-(+)-hydrogen tartrate separates as prismatic crystals.2

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