5. Answer the questions for the following experimental data:
4
H
O
87% yield (racemic)
0 °C
Me
H
O
160 °C
Me
H
PE = 22.0 kcal/mol
A
PE = 12.5 kcal/mol
160 °C
O
76% yield (racemic)
PE = 11.6 kcal/mol
B
Me
H
a. What kind of reaction is this? 2 pts
b. Draw the appropriate transition states and account for the formation of A and B, citing any pertinent structural
effects/rules. 10 pts
formation of A
formation of B
c. It appears that one of the products is formed under kinetic control and one is formed under thermodynamic
control. Use a potential energy diagram to illustrate these designations; be sure to annotate your PE diagram to alert
the viewer to any important aspects of this process. 10 pts
d. Why is the PE different for compounds A and B? Analyze using well-drawn (i.e., 3D) organic structures. 8 pts
6. Devise a synthesis of isotopically labelled meso-2,3-butanediol starting with acetylene and methane. The
isotopic labeling that the "front office" wants is this: each molecule should contain one 16O and one 17O isotope.
Hint: 17O labeled water is cheap. 10 pts
HO
OH
meso-2,3-butanediol
7. It is a little known fact that Jeopardy's Alex Trebek was an organic chemist
before becoming TV's most famous quizmaster. Provide the correct
questions to Trebek's following answers: (3 pts each letter)
a. An alkene-to-alcohol synthesis which is Markovnikov and NOT
subject to intermediate rearrangements.
What is _________________________________________________?
b. A method for separating a mixture of enantiomers via diastereomeric complexation.
Alex Trebek
What is _________________________________________________?
c. Two types of strain associated with the instability of cyclopropane.
What are _________________________ and __________________________?
d. pKa of an acetylenic hydrogen and a base strong enough to quantitatively ionize this to the carbanion.
What is __________________ and ___________________________________?
e. Approximate barrier to ring inversion in cyclohexane.
What is ____________________ kcal/mol?
f. Approximate cost to homolytically break (±15 kcal/mol) a C-H bond.
What is ____________________ kcal/mol?
g. The number of chemical steps (±3) to make Merck's HIV protease inhibitor Crixivan.
What is _____________________?
h. Explaining the orange color of carrots to Uncle Wayne merits this one-sentence zinger:
The color is due to____________________________________________________________________
___________________________________________________________________________________?
i. Strategy one might adopt when forming the Grignard from 2-bromoethanol fails.
What is ______________________________________________________?
5
X. Predict the outcomes of the following reactions
HO
OH
CO2H
1. BH3:THF
2. H2O2, NaOH
3. PCC, DCM
1. LiAlH4
2. NH4Cl, H2O
3. H2/Pt
4. H2CrO4
1. mCPBA
2. PhMgBr, ether
3. H+ work-up
4. Jones reagent
1.
O
H
heat
2. NaBH4, ether
3. NH4Cl, H2O