Stereochemistry

Stereochemistry Quiz #4

Question The molecules above are (Z) configurations. True (A) False (B)

Question Indicate the relationship of the pair of molecules shown. A. same molecules B. mirror images C. different molecules D. constitutional isomers E. cis and trans isomers

Question Consider the molecule below.What is the maximum number of methyl groups that can be in the equatorial position at the same time? A. 0 B. 1 C. 2 D. 3 E. 4

Question Both cis- and trans-1,2-dimethylcyclohexane are chiral. True (A) False (B)

Question How many of the following compounds contain an internal mirror plane of symmetry? A) 1 B) 2 C) 3 D) 4

Question Which of the following molecules is chiral? B A C D

Question What is the stereochemical designation of the following molecule? A. (R)B. (S)C. non-chiral (achiral)

Question Indicate the relationship of the pair of molecules shown. A. same moleculesB. enantiomersC. diastereomersD. different moleculesE. constitutional isomers

Question H B A The S-isomer is an effective sedative. The R- is a teratogen in humans, but not rats. In the structures above, which is the R-isomer, A or B?

Question What is the stereochemical designation of the following molecule? A. (R)B. (S)C. non-chiral (achiral)

Question What is the stereochemical designation of the indicated chirality center? A. (R)B. (S)C. non-chiral (achiral)

Question Indicate the relationship of the pair of molecules shown. A. same moleculesB. enantiomersC. diastereomersD. different moleculesE. constitutional isomers

Question:Calculate []D • A 1.00-g sample is dissolved in 20.0 mL ethanol. 5.00 mL of this solution is placed in a 20.0-cm polarimeter tube at 25C. The observed rotation is 1.25 counterclockwise. []D = A) -1.25 B) -6.125  C)-12.5  D) +61.25 

Question A sample of a pure R- enantiomer has a specific rotation of – 40°. A mixture of R-/S- enantiomers has an observed optical rotation of + 22°. What is the % ee of the mixture? A. 55 % ee R B. 55 % ee S C. 18 % ee R D. 0.55 % ee R E. none of the above

Question If a sample is 50 % ee of R stereoisomer, what is the % R in the mixture? A. 50B. 100C. 25D. 75

Question If a chemical reaction produces a mixture of 80% R and 20 % S, what is the % ee? • 80 • 60 • 20 • 10 • 4

Question If a sample of the pure R enantiomer of a molecule has a specific rotation of – 40° what is the specific rotation of pure S? • –60° • +60° • –40° • +40° • cannot be determined

Question If the specific rotation of (R)-2-methylhexan-2-ol is –35°, what is the specific rotation of (S)-hexan-2-ol? +35° –35° It is negative but value cannot be determined. It is positive but value cannot be determined. It cannot be determined.

Question If a sample of the pure R enantiomer of a molecule has a specific rotation of – 40° and an enantiomeric mixture of that molecule has an 82% ee S, what shoulld be the observed specific rotation of the sample? +40° +8.2° +32.8° –48.7° cannot be determined

Question Calculate the relative proportions of (+)-2-butanol, []D = +13.5o, and (-)-2-butanol, []D = -13.5o, required to give a specific rotation of +0.45o. 50% R : 50% S 90% R : 10% S 3.3 % R : 92.7% S 52% R : 48% S cannot be determined

Stereochemistry