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Analysis of KH/KD and Mechanism Predictions and Chirality

1. Label all prochiral hydrogens (including Re and Si faces) in R-2,4-dimethyl-3-heptanone.

2. Consider the asymmetric deuteration shown below.
a. To which face of the prochiral double bond did the deuteriums add to?
b. Assign configurations to all chiral centers in the molecule.
c. Assign E/Z configuration to the starting alkene.

3. The classic work of Westheimer (1953) on yeast alcohol dehydrogenase is shown below:
Acetaldehyde may be replaced by 2-butanone to give the following reaction.
2-butanone + NADD ----> S-2-D-butanol + NAD+
a. Draw absolute configurations of 2-butanone and S-2-D-butanol.
b. Label all homotopic, enantiotopic and diastereotopic hydrogens.
c. Show the Re and Si faces of the ketone.
d. Show clearly to which face the D was transferred?
e. Apply 2-butanone to the diagram above.
f. Discuss geometrical differences presented by 2-butanone.

4. The following kH/kD values were observed for epoxidation of the following peracid.
a. Identify as to type, etc
b. Are the results consistent with what is usually considered to be the transition state in peracid epoxidations?

5. The monoxygenase (enzymatic) oxidation of naphthalene to the alpha-hydroxynaphthalene (alpha-naphthol) is thought to occur via a NIH shift mechanism with an epoxide intermediate. Show the possible steps and predict the effect of replacing a H with a D at the alpha position. Show the labeled product.

6. Predict the mechanism and reaction type of the following. Discuss kH/kD values.
a. PhCH2CH2NMe3 + OEt- ---> PhCH=CH2 + NMe3
b. (CH3)3CBr + EtOH + heat ---> H2C=C(CH3)2
c. (CH3)3CBr + EtOH/H2O ---> (CH3)3COH
d. a substituted biphenyl ----> racemization

7. Interpret the following kH/KD results
PHCH2NO2 + NMe3 ---> PhCH-NO2 + HNMe3+ kH/KD = 50

8. Consider the isomers below. Which undergoes reaction faster? Suggest a mechanism and the possible products?
a. cis and trans-1-bromo-4-t-butylcyclohexand + EtOH/H2O ---->
b. cis and trans-4-t-butyl-1-hydroxycyclohexane + acetic anhydride ---->
c. endo and exo-2-norbornyl bromide + acetic acid ---->

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Solution Summary

Detailed answers are given to many questions relating to prochirality and kinetic isotope effects. Many mechanisms and diagrams are included.

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