Chirality 1+2

Question 1

What are stereoisomers?

Answer 1

• same molecular formula but different spatial arrangements

Question 2

What are diastereomers ?

Answer 2

• Stereoisomers that are not mirror images of eachother

Question 3

What are enantiomers ?

Answer 3

• Nonsuperimposable mirror images of each other

Question 4

Features of constitutional isomerism?

Answer 4

• Same formulae but different connectivity (structural) isomers
• different chemical+ physical properties
• can not interconvert

Question 5

What is geometric isomerism?

Answer 5

• Cis and trans isomers
• same group on either side

Question 6

What are the CIP rules ?

Answer 6

• Prioritise according to atomic number
• same side = Z , opposite = E

Question 7

Are stereoisomers interconvertible?

Answer 7

• Not interconvertible

Question 8

What is a chiral carbon?

Answer 8

• usually sp 3 hybridised
• has 4 different groups attached to it
• form enantiomers

Question 9

What is the R configuration?

Answer 9

• clockwise order
• lowest priority group 4 should be going away from you - on dash bond

Question 10

What is the S configuration?

Answer 10

• priorities move in anti-clockwise order - number 4 at back on dashed bond

Question 11

What do we do if priority atom 4 not at back?

Answer 11

• assign chirality as usual then reverse answer

Question 12

Similarities of R and S isomers

Answer 12

• identical physical + chemical properties
• eg.pka, bp,mp, solubility

Question 13

What is an achiral carbon ?

Answer 13

• superimpossible

Question 14

What do wedge bonds do ?

Answer 14

• approach you

Question 15

What are L amino acids ?

Answer 15

• amine group is on the left

Question 16

What is D amino acid ?

Answer 16

• amine group to the right

Question 17

What is L glucose ?

Answer 17

• OH group to the left

Question 18

What is D glucose ?

Answer 18

• OH to the right

Question 19

What is a erythro enantiomer?

Answer 19

• same group on same side on Fischer projection

Question 20

What is a threo enantiomers?

Answer 20

• same group on opposite sides on Fischer projection

Question 21

2 differences in properties of enantiomers ?

Answer 21

• rotation of plane polarised light (PPL)
• interaction with other chiral molecules

Question 22

What is plane polarised light?

Answer 22

• Produced by passing light through a polarising filter
• rotation of PPL measured in degrees

Question 23

Rotation of PPL by enantiomers

Answer 23

• enantiomers rotate the plane of the PPL by equal amounts but in opposite directions

Question 24

What is an enantiomeric excess ?

Answer 24

• Amount of pure enantiomer in excess of the racemic mixture

Question 25

Enantiomers Interaction with Other Chiral molecules

Answer 25

• (R)-enantiomer active binds
  correctly to receptor to trigger
  response
• (S)-enantiomer cannot bind
  correctly, does not trigger
  response

Question 26

What is a meso compound?

Answer 26

• molecule has an internal plane of symmetry so its achiral

Question 27

what are the equations to enantiomeric excess ?

Answer 27

• % enantiomeric excess = moles of one enantiomer - mole of other enantiomer / total moles of both enantiomers X 100
• % enantiomeric excess = observed specific rotation / specific rotation of pure enantiomer X 100