CH 201 Name ______________________________

Exam #2

October 11, 2002

Page Points

1 ______ (09) DGo = DHo - T DSo

2 ______ (17) DGo = -R T ln K (R = 0.008317 KJ mole-1degK-1)

3 ______ (12)

4 ______ (25)

5 ______ (16)

6 ______ (14)

7 ______ (07)

Total ______ (100)

1. (a) Provide IUPAC names for the following molecules utilizing the cis trans nomenclature. (9 pts)

(b) Provide IUPAC names for the following molecules. Don't forget to indicate stereochemistry when applicable (i.e R or S). (6 pts)

(c) (6 pts) Provide structures for the following molecules.

trans-1,2-Diisopropylcyclopentane R-2-bromobutane

2. Draw the two chair conformations for cis-1-t-butyl-4-ethylcyclohexane and circle the most stable conformer. (5 pts)

3. (a) (5 pts) Draw the two chair conformations for trans-1-methyl-3-isoproplycyclohexane showing all bonds to the cyclohexane carbons explicitly and label the substituents as axial or equatorial (methyls may be written as CH3). (clarity counts!) Circle the most stable conformer.

(b) If each methyl in an axial position is worth 7.6 kJ of strain energy and an isopropyl is worth 9.39 kJ what is the energy difference (DG) between the two isomers in part a? (2 pts)

(c) What is the equilibrium constant K between the conformational isomers at 2980K? (3 pts)

(d) How much of each isomer is present at equilibrium? (2 pts)

_________% isomer on the left

_________% isomer on the right

4. Draw Newman projections for all the conformational isomers for 1-bromopropane looking down the C1-C2 bond starting with the conformation shown. (Rotate the back carbon clockwise) (6 pts)

Using the diagram below label the Newman projections above with the appropriate number (4 pts)

4. Using the R and S convention, assign the absolute configuration of every stereocenter (marked with an asterisk) in each of the following molecules. (15 pts)

5. Give the stereochemical relationship between Compound A below and the five compounds below it by writing the word "enantiomer," "diastereomer," "identical," or "constitutional isomer" in the appropriate blanks. IGNORE DIFFERENCES IN CONFORMATION. (10 pts)

6. Label the following molecules as chiral or achiral. (6 pts)

a) 3-methylpentane _________________

b)

_________________

c)

__________________

7. Circle the compound with the higher boiling point? (6 pts)

a. CH3CH2Br or CH3CH2F

8. Circle the compound with the greatest heat of combustion: (8 pts)

a.

b.

c.

d. What is the responsible for the difference in heat of combustion for the molecules in part c?

Torsional strain, ring strain or steric strain? ___________________

9. An enantiomerically pure sample of (S)-(+)-2-Butanol shows a specific rotation of +13.52o. A mixture of the 2-butanol enatniomers showed a specfic rotation of -5.42o. Calculate the %EE of the sample.

%EE = __________ (3 pts)

What is the actual compostion of the mixture? _______% S and _________%R (4 pts)