Organic Chemistry
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The specific rotation of the S enantiomer of a proposed cancer treatment drug is −26.9°. A researcher attempted to synthesize an enantiopure form of the said drug but synthesized it with a specific rotation of −22.7°. Determine the S to R ratio of the drug synthesized by the researcher.
Thalidomide is a drug used to treat cancer, several skin disorders, and particular complications caused by human immunodeficiency virus (HIV). The (–)-isomer is the biologically active form of thalidomide. A sample of a mixture of thalidomide has a specific rotation of [α]D = –45.1°. Using the specific rotation of the pure enantiomer below, determine the ratio of (+)- to (–)-thalidomide in the sample.
Limonene is a volatile liquid found in citrus fruits. The (R)-enantiomer is used as a flavoring agent in foods and fragrances in the cosmetic industry. Pure (R)-Limonene has a specific rotation ([α]D) of +115.0°. Predict the specific rotation of a mixture that contains 82% R and 18% S.
A commercial drug has an enantiomeric excess of 86% of R isomer. Determine the percentage of the S isomer.
A solution of pure (R)-2-bromobutane has a specific rotation of -23.1°. If a mixture of stereoisomers of 2-bromobutane shows a specific rotation of −14°, determine the percentage of (R)- and (S)-2-bromobutane in it.
A sample enriched with the R enantiomer has a %ee of 76%. What percentage of the sample is racemic? What is the S to R ratio of the enantiomers in the sample?
A substance has a specific rotation of -40.0°. In a polarimeter tube that is 5 cm long, a solution of the compound (0.81 g/100mL) causes an observation of the rotation of -7.52°. How much of each enantiomer is in the solution?
An unknown drug has a specific rotation of +82°. The commercial synthesis of this drug results in a mixture with an enantiomeric excess of 94%.
i. Determine the absolute configuration (R or S) of this drug.
ii. What is the percentage of each of its enantiomers in the commercial product?
When (R)-2-chlorobutane is boiled with excess ammonia, it undergoes a substitution reaction. If SN1 substitution occurs twice as fast as SN2, determine the enantiomeric excess and the specific rotation for the product. Assume that the two enantiomers are produced equally from the SN1 substitution. The specific rotation of (R)-butan-2-amine is –7.5°
(S)-2-chloropentane has a specific rotation of +34.07°.
(i) Show the structure of (S)-2-chloropentane.
(ii) What is the specific rotation of (R)-2-chloropentane.
(iii) If a sample containing (R)- and (S)- 2-chloropentane has a specific rotation of –12.47°, calculate the percentage composition of the sample.
The specific rotation of D-(+)-glucose is +52°. If we have a solution with an observed optical rotation value at +26°, what percentage does D-(+)-glucose contribute to this solution?