Name:

Quiz 4 – Summer 2009

Problem 1 (10 points): Circle each chirality center in the molecules below, and assign the correct stereochemical identifier (R or S) to each. Name the first molecule according to IUPAC rules with the correct stereochemistry.

Cl F

CH3OH

Cl

H

Problem 2 (4 points): Answer the following questions based on the three stereoisomers of

1,2,3,4-tetrabromobutane.

(a) One isomer is sweet and has an optical rotation of 0°. Circle the sweet isomer.

(b) A mixture of the two non-sweet compounds (which are enantionmers) has a

specific rotation of 9°. The R,R isomer has a specific rotation of 12°. What is the

enantiomeric excess?

Problem 3 (2 points): A second category of six-carbon carbohydrates, called ketohexoses, has

the constitution shown. How many stereoisomeric 2-ketohexoses are possible?

Problem 4 (16 points): In the box below each pair of molecules, write the letter(s) for each label from the list below which applies to the molecules. Be careful: many (most) pairs fit more than one descriptor, so be sure to write any and all applicable letters. Also note that for every pair, you should write either "J" or "K", since all molecules are either chiral or achiral. All letters will not necessarily be used. Also, for I, J, and K, both compounds or neither will be meso, chiral, or achiral. Do not put letters which are not applicable -- points will be taken off for each incorrect letter.

A. Not isomers E. Conformational isomers I. Meso compounds B. Identical compounds F. Configurational isomers J. Chiral C. Constitutional Isomers G. Enantiomers K. Achiral D. Stereoisomers H. Diastereomers

OH Cl OH Cl

OH OH