3.30: Quiz 6A Key

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Clearly indicate true (T) or false (F) for the following statements (2 pts each):

__F__	Enantiomers of a compound will have different boiling points.
__T__	A chiral catalyst or enzyme can be used to synthesize a single enantiomer product.
__T__	A primary carbon is less sterically hindered than a tertiary carbon, which explains why a primary alkyl halide reacts faster than a tertiary alkyl halide in an S_N2 reaction.

(2 pts each) Multiple Choice/fill-in-the-box (choose the best answer from the options given):
1. Which of the following reactions will give a racemic product?
  1. An achiral Rh metal complex for the hydrogenation reaction of an alkene
  2. A reaction with the enzymes in Bakerʼs yeast
  3. An enzyme that only recognizes a trans alkene substrate
  4. A chiral Rh metal complex for the hydrogenation reaction of an alkene
2. What is the chemical reason for the controversy regarding the use of methyl iodide as an agricultural fumigant?
  1. Methyl iodide is a racemic molecule and one enantiomer has toxic side-effects.
  2. Methyl iodide catalyzes the hydrolysis reaction of DNA, making it toxic.
  3. Methyl iodide is an electrophile that will alkylate DNA, making it toxic.
  4. Methyl iodide makes strawberries taste bad.
3. Stereoisomers with an asymmetric carbon center and non-superimposable mirror images are:
  1. cis/trans isomers
  2. enantiomers
  3. constitutional isomers
  4. end-of-the-quarter isomers
  5. regioisomers
4. A 50:50 mixture of two enantiomers is called a ____________
  1. memorial day mixture
  2. cis/trans mixture
  3. mirror image
  4. constitutional mixture
  5. racemic mixture
5. (2 pts) What carbon building block does nature use to synthesize the following product(s)?

1. (6 pts) How many asymmetric carbon centers does each of the following molecules have?

(6 pts) Indicate for the following pairs of compounds whether they are identical, constitutional isomers, or enantiomers. (put your answer in the box provided – you may use an answer more than once, or not at all)

1. (2 pts) Provide a brief definition indicating what factors make a molecule a good nucleophile.

The molecule should have high electron density (π bonds, lone pairs) that is readily available to make new bonds (delocalized e^- is less available).

(4 pts) Circle which molecule is a better nucleophile and briefly explain your answer.

Nitrogen is less electronegative than oxygen, therefore it won't stabilize the negative charge as well, making A a better nucleophile.

1. (5 pts) Identify the asymmetric carbon center in the molecule shown below and then draw a perspective structure for each enantiomer.
2. (3 pts) The (R)-enantiomer of an amine molecule is shown below. Draw the perspective structure for the (S)-enantiomer (ie, the other enantiomer) in the box provided.

Extra Practice:
1. (4 pts) Draw the racemic mixture (both enantiomers) that result upon hydrogenation of the following alkene with an achiral catalyst.

(2 pts) How would you expect the reaction to be different if a chiral Rh catalyst is used?

You would form only one enantiomer.