Stereochemistry

Question 0

What is an achiral object?

Answer 0

An object that lacks chirality; that is, and object with a superposable mirror image

Question 1

What are chiral molecules?

Answer 1

Molecules that are not superposable on their mirror images

Question 2

What are isomers?

Answer 2

They are molecules that have the same molecular formula but possess different structures because of different connectivity of atoms and/or spatial arrangement of atoms

Question 3

What are constitutional isomers?

Answer 3

Are molecules that have the same molecular formula but have different connectivity of atoms

Question 4

What are stereoisomers?

Answer 4

They are isomers that have the same connectivity of atoms but have a different spatial arrangement of their atoms

Question 5

What are conformational isomers?

Answer 5

They are stereoisomers that interconvert by rotation along single bonds

Question 6

What are configurational isomers?

Answer 6

They are stereoisomers that do not interconvert at room temperature by virtue of having to break either single or double bonds to interconvert

Question 7

What are enantiomers?

Answer 7

They are stereoisomers that are non-superposable mirror images

Question 8

What are diastereomers?

Answer 8

They are stereoisomers that are not mirror images

Question 9

What are atropisomers?

Answer 9

They are enantiomers or diastereomers that differ because of hindered rotation along a single bond

Question 10

What is a stereocenter?

Answer 10

It is an atom about which exchange of two groups produces a stereoisomer

Question 11

For a molecule with “n” chiral centers, the maximum number if stereoisomers possible is:

Answer 11

2^n

Question 12

1. ) Two stereoisomers are ________ if ALL of the chiral centers have the opposite configuration (R vs. S)
2. ) If even one chiral center is the same between two stereoisomers, they are _______

Answer 12

1. ) Enantiomers

2. ) Diastereomers

Question 13

A compound that contains TWO or more chiral centers bonded in such a way that it is achiral is a ________

Answer 13

Meso compound

Question 14

Light that oscillates in parallel planes are _____?

Answer 14

Plane-polarized

Question 15

An optically active compound does what?

Answer 15

Rotates the plane of plane-polarized light

Question 16

What is observed rotation of light?

Answer 16

The number of degrees the plane of plane-polarized light is rotated

Question 17

What is specific rotation?

Answer 17

It is the observed rotation measured in a cell 1 dm long and at a sample concentration of 1 g/mL

Question 18

What is a dextrorotatory compound?

Answer 18

A compound is dextrorotatory if the analyzing filter must be turned clock-wise to restore the zero point

Question 19

What is a levorotatory compound?

Answer 19

A compound is levorotatory if the analyzing filter must be turned counter-clockwise to restore the zero point

Question 20

Each member of a pair of ______ rotates the plane of plane-polarized light an _______ number of degrees but in the _______ direction

Answer 20

1. ) Enantiomers
2. ) Equal
3. ) Opposite

Question 21

What is a racemic mixture?

Answer 21

It is a mixture of equal amounts of two enantiomers and has a specific rotation of zero

Question 22

How do you calculate the percent of optical purity (or the enantiomeric excess)?

Answer 22

It is the (specific rotation if a mixture of enantiomers) / (specific rotation of the pure enantiomer) x100

Question 23

_________ are not chiral, so they are optically inactive

Answer 23

Meso Compounds