Organic

Question 1

Conformation Isomers

Answer 1

Differ by rotation about a single sigma bd

Question 2

Stereoisomers

Answer 2

Differ by spatial 3-D arrangements

Question 3

Constitutional(or Structural) Isomers

Answer 3

Differ by the positions of atoms
- 2-chlorobutane vs.
3-chlorobutane

Question 4

Geometric Isomers

Answer 4

Cis-2-butene vs Trans-2-butene

Question 5

Enantiomers

Answer 5

Nonsuperimposeable, chiral mirror images

- L-lactic acid vs. R-lactic acid

Question 6

Diastereomers

Answer 6

Stereoisomers that are not mirror images of each other.

Geometric isomers are also diastereomers.

Question 7

Racemic mixture

Answer 7

A 50-50 mixture of a pair of enantiomers

Question 8

Racemization

Answer 8

The conversion of one pure enantiomer to a racemic mixture

Question 9

Meso compound

Answer 9

A meso compound is one that has chiral centers, but over all the molecule is not chiral.

They posses an internal mirror plane through the center of the molecule.

The mirror images of the molecule is superimposable.

Question 10

Heterolytic cleavage

Answer 10

Cleavage of a covalent bond where 2 bonding electrons are taken by one atom.

This results in the formation of a cation and an anion

Question 11

Homolytic cleavage

Answer 11

The cleavage of a covalent bond where one bonding electron is taken by each atom

Br-Br -> Br• + Br•

Question 12

Rank carbocation stability

Answer 12

3>2>1>methyl

Question 13

Rank carbocation reactivity

Answer 13

Methyl>1>2>3

It’s opposite of the carbocation stability!

Question 14

Sn1 mechanism

Answer 14

Rate = k[RX]

Unimolecular reaction

Results in a trigonal planar carbocation which can be attacked from both sides by a nucleophile, which results in a racemic mixture (50% R, 50%S)

Question 15

Identify enantiomers

Answer 15

Rank substituents according to mass

If 1 to 2 to 3 rotates to the right (or CW) it is R

If 1 to 2 to 3 rotates to the left (or CCW) it is S

Question 16

Optical rotation

Answer 16

If the plane polarized light is rotated to the left by the chiral center, the molecule is assigned “l” or “negative degrees of rotation”

If plane polarized light rotates to the right it is assigned “d” or “positive degrees of rotation”

Note: R and S enantiomers rotate ppl in equal magnitudes, however the rotation is in opposite directions

Question 17

Does a racemic mixture rotate plane polarized light?

Answer 17

No. It is optically inactive.

Question 18

E2 mechanism

Answer 18

Rate = k[base][substraight]

Rxn proceeds through 1 step. There is no carbocation intermediate.

Question 19

Elimination rxns: Define Saytzeff and Hoffman products

Answer 19

Saytzeff: the eliminated beta H+ comes from the more substituted beta C (generally the major product)

Hofmann: the eliminated beta H+ comes from the less substituted beta C

Question 20

When will the Hofmann product dominate an elimination rxn?

Answer 20

The less substituted alkene will dominate the rxn as a result of steric hinderance due to:

1: the size of the attacking base
2: the size of the group surrounding the LG

Question 21

CH3Cl + (n-C4H9)3SnH ->

Answer 21

CH4 + (n-C4H9)3SnCl

Question 22

CH3MgBr + H2O ->

Answer 22

CH4 + Mg(OH)Br

Question 23

Areomatic if:

Answer 23

Pi e- = 4n + 2

Huckel numbers!
- 2, 6, 10, 14….

Question 24

Antiareomatic if:

Answer 24

Pi e- = 4n