Problem Set 6
Chapter 7
Due: Monday, February 27, 2006
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? 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. A student proposes to study an
elimination reaction. She has access to the hindered base
1, both as its meso diastereomer and as its two
enantiomers. 5. 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 queries in d) and
e)
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.
a) Draw each of these bases with their CIP designations.
b) She reacts one of the optically active bases with
cis-1-bromo-4-tert-butylcyclohexane (2) to provide a
sample of 3 rich in the dextrorotatory enantiomer.
When the same experiment is conducted with the enantiomeric
base 1, a sample of 3 is isolated with the
opposite rotation. When meso-1 is employed, product
3 has no rotation. Without concern for which
enantiomer of 1 provides which enantiomer of
3, explain and illustrate what is going on
here.