Comprehensive Organic Chemistry - Chem 225b

Problem Set 6

Chapter 7

Due: Monday, March 3, 2008

1. Consider the optically active diastereomer (1S, 2R)-1-bromo-1,2-dideuteriopentane (1).

a) What is the major product formed when 1 is exposed to CH3ONa/CH3OH? Provide the name and mechanism? Is it optically active?
b) Is there a significant isotope effect in a)? Explain.
c) When t-C4H9OK/t-C4H9OH is used in a) instead of CH3ONa/CH3OH, different major product is formed. Name it, draw it and provide a mechanism for its formation. Is it optically active?
d) Is there a significant isotope effect in c)? Explain.
e) What is the major product formed with an optically active diastereomer of 1 having the configuration (1S, 2?) when it is exposed to the conditions of a)? Name and draw it.
f) What is the major product formed with an optically active diastereomer of 1 having the configuration (1S, 2?) when it is exposed to the conditions of c)? Name and draw it.
 

Biot examining Pasteur's tartrate crystals 

 

2. Provide the products in each of the following questions and mechanisms for their formation. Pay attention to stereochemistry. Be explicit about enantiomers.

 

3. The monochlorination products from the free radical chlorination of 3-methylpentane are isolated.

a) Draw all constitutional isomers and diastereomers. Identify the racemates and achiral compounds. Briefly explain why.

b) Each chloride reacts with aqueous NaOH. Compounds A and B give the largest ratio of SN2/E2 products (SN2 products C and D, and E2 products G and K, respectively). Compound E gives F (ΔHfo = -14.8 kcal/mol) and G while chloride H gives I (ΔHfo = -15.8 kcal/mol) and G. The ratios F/G and I/G are greater than unity. Compounds F, G and I have one degree of unsaturation. Chloride J reacts much faster with water than do chlorides E and H. Chloride J gives more I than F and more I than K. What are the structures A-K? Explain and illustrate.


4. Provide reagents for accomplishing the following reactions. Some of them may require more than one step. Show any intermediate compounds. Comment briefly on your choices---mechanisms?, etc. Answer the query in d).