Organic Chemistry Stereochemistry and Reactions

Question 1

How can you calculate the total number of stereoisomers a molecule contains?

Answer 1

2^n where n in the number of chiral molecules.

Question 2

Enantiomer short cuts:

Answer 2

1. If two atoms are switched, then it is an enantiomer.

2. Back planar, or out 4th group is a reverse.

Question 3

What is the key for sp2 molecules that are attacked?

Answer 3

The molecule can either bind to the top or bottom, which leaves you with an enantiomer.

Question 4

What is nucleophilic substitution?

Answer 4

The attack of an electropositive molecule by a nucleophile. Two types Sn1 (2 steps) & Sn2 (1 step)

Question 5

What is a nucleophile?

Answer 5

The molecule donating the electrons, so it’s the same thing as the lewis base.

Question 6

What makes a good leaving group?

Answer 6

A good leaving group has a stable conjugate when it has left. The more acidic (weak base) the conjugate is, the better the leaving group. Or a weak bond can create a good leaving group.

Question 7

What are the characteristics of Sn2 reactions?

Answer 7

1. Prefer primary, second, over tertiary.
2. Favors aprotic solvents
3. No racemic mixture, inversion of stereochemistry
4. 2nd order kinetics involving both molecules
5. 1 step.

Question 8

What are the characteristics of Sn1 reaction?

Answer 8

1. Prefers tetiary, secondary, primary.
2. Favors protic solvents
3. Nucleophile attacks sp2 carbocation, which leaves an enantiomer, rearrangement.
4. 1st order involving just the electrophile.
5. 2 steps

Question 9

How do the energy diagrams for SN1 and Sn2 differ?

Answer 9

Sn1 has an intermediate so it will have two humps.

Question 10

Properties of enantiomers and diasteromers.

Answer 10

Enantiomers have the same physical and chemical properties, besides light rotation.
Diastereomers have different physical and chemical properties.