Take a few moments to look over the exam. Answer each question on the exam paper.

Important clues and structures are in bold.

Do all preliminary drawing or computations on the work sheets at the end of the exam. The

work sheets will not be graded. There is a Periodic Table on the last page of the exam.

The exam is 55 minutes.

STOP writing and hand in your exam when you are asked to do so.

REMEMBER: Neatness is to your advantage.

1. (20 pts) ______

2. (20 pts) ______

3. (20 pts) ______

4. (20 pts) ______

5. (20 pts) ______

_________________________

Total (100 pts)

1. (20 pts) Compound A, C₇H₁₄O, is a 1,3-disubstituted cyclohexane. The difference in

energy between its two chair conformations is 0.7 kcal/mol. [DG^o (kcal/mol) values for

axial and equatorial substituents in mono-substituted cyclohexanes: -CN, 0.2; -Cl, 0.5;

-OH, 1.0; -COOH, 1.4; -CH₃, 1.7; -C₂H₅, 1.8.]

a) (6pts) What are the two groups attached to the cyclohexane ring? Briefly explain your

reasoning.

b) (6pts) Is this 1,3-disubstituted cyclohexane a cis or trans isomer? Explain briefly.

 

c) (8pts) Using the template below, add the groups to the cyclohexane rings paying

attention to the position of the equilibrium. Briefly explain your reasoning.

 

2. (20 pts) Vinyl acetylene 1, is an important intermediate in the preparation of synthetic

rubber. Draw a molecular orbital representation of 1. Include and indicate the

hybridization of carbon atoms, the location of p-bonds, and an overall description (in a

single word) of the shape of the molecule.

3. (20 pts; equal weight) Circle the best answer(s) in each of the following questions.

a) The dihedral angle in gauche butane

0o

30o

60o

120o

180o

b) Compounds with a net dipole moment

c) The least acidic of the following compounds

CH3CO2H

CCl3CO2H

HCl

C2H6

NH3

d) The 19th century chemist who concerned himself with stability of cycloalkanes.

Baeyer

Berzelius

Kekule

Liebig

van't Hoff

e) The dibromocyclohexanes that have two equatorial substituents in their most stable chair

conformation.

4. (20 pts) For the eclipsed and staggered conformations of 2-methylpentane viewed along the

C2-C3 sigma bond, draw a Newman projection of the most stable eclipsed and staggered

conformations. Place the appropriate energies in the Newman projections below. [Use the

circles as templates for the Newman projections.] Calculate the energy (kcal/mol) of both

conformations. Place your answer in the appropriate box. Show work. [H/H, eclipsed, 1.0

kcal/mol; CH₃/H eclipsed, 1.3 kcal/mol; C₂H₅/H, eclipsed, 1.4 kcal/mol; CH₃/CH₃, eclipsed,

3.0 kcal/mol; CH₃/CH₃, gauche, 0.9 kcal/mol; CH₃/C₂H₅, gauche, 1.0 kcal/mol.]

5. (20 pts) Complete the following: