Test Bank For Organic Chemistry With Biological Applications International Edition 2nd Edition

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Test Bank For Organic Chemistry With Biological Applications International Edition 2nd Edition

Chapter 5 – Stereochemistry at Tetrahedral Centers

Match each definition to a term from the list below. Place the letter of the term in the blank to the left of the definition.

a. racemates f. meso compounds

b. chirality center g. optically active

c. chirality h. prochirality center

d. diastereomers i. optically inactive

e. enantiomers j. achiral

1.           describes organic molecules which rotate plane-polarized light.

ANS: g or e

2.           are designated either (±) or d,l.

ANS: a

3.           are stereoisomers that are not mirror images.

ANS: d

4.           is an atom in a molecule that is bonded to four different atoms or groups of atoms.

ANS: b

5.           are molecules which contain both chirality centers and a plane of symmetry.

ANS: f

6. _____ describes an sp³-hybridized atom that can become a chirality center by changing one of its attached groups.

ANS: h

7. Which of the following physical properties can be used to identify a compound?

a. R

b. S

c. a

d.

ANS: d

8. Which of the following has a plane of symmetry?

a. boot

b. laboratory beaker

c. hammer

d. both b and c

e. none of the above

ANS: d

9. If (+)-sucrose has a specific rotation of +66.47, what is the specific rotation of (-)-sucrose?

a. +66.47

b. -66.47

c. +33.43

d. -33.43

e. Must be determined with a polarimeter.

ANS: b

10. (-)-cholesterol

a. does not have a chiral center.

b. is dextrorotatory

c. rotates the plane of polarized light counterclockwise.

d. does not rotate polarized light.

ANS: c

11. The biological importance of enantiomers arises from?

a. Biological reactions involve receptor molecules.

b. Biological receptors are chiral.

c. Biological receptors require a specific enantiomer for reaction.

d. Each enantiomer has different biological properties.

e. all of the above

ANS: e

12. 2.10 g of an unknown compound was dissolved in 15.00 mL of ethanol.  The sample was placed in a 10.0 cm cell in a polarimeter and the angle of rotation was determined to be -18.48^o.  What is the specific rotation of this unknown and specify if the compound is levorotatory or dextrorotatory?

ANS: -132 and levorotatory

Place asterisks at all the chirality centers in each molecule below.

13.

ANS:

14.

ANS:

15.

ANS:

16. Rank the following substituent groups from highest to lowest priority according to the sequencing rules.

CO₂CH₃ CO₂HOHCl

ANS:

Cl   >   OH   >   CO₂CH₃    >   CO₂H