Chirality 1 & 2

Question 1

What are stereoisomers?

Answer 1

Isomers with same molecular formula + same connectivity of atoms BUT different spatial arrangement

Question 2

Describe constitutional isomerism

Answer 2

Molecules with same formula but different connectivity

Question 3

What can constitutional isomers not do?

Answer 3

Interconvert

Question 4

What are examples of constitutional isomers?

Answer 4

Aspirin
Caffeic acid
4-hydroxyphenyl-pyruvic acid

Question 5

What is geometric isomerism?

Answer 5

Cis + trans

Same formula, same connectivity of C skeleton but different spatial arrangement of substituents around alkane

Question 6

What is cis?

Answer 6

Same face

Question 7

What is trans?

Answer 7

Opposite faces

Question 8

When is there no interconversion between cis + trans?

Answer 8

At ambient or body temp

Question 9

What temp is required for cis + trans interconversion?

Answer 9

180 degrees

Question 10

What is the cis form of C4H4O4?

Answer 10

Maleic acid

Question 11

What is the trans form of C4H4O4?

Answer 11

Fumaric acid

Question 12

What is the Cahn-Ingold-Prelog naming system?

Answer 12

Prioritise 2 substituents according to their atomic number of atom directly attached to C

Question 13

What is it if priority groups 1 are on same face?

Answer 13

Z

Question 14

What is it if priority groups 1 are on opposite faces?

Answer 14

E

Question 15

What does stereoisomers normally have?

Answer 15

Chiral C

Question 16

What is a chiral carbon?

Answer 16

Stereocentere = stereogenic C

Question 17

What is optically inactive?

Answer 17

Achiral

Question 18

What is a racemic mixture?

Answer 18

1:1 mix of enantiomers

Question 19

What happens if it is a mirror image?

Answer 19

Non-superimposable

Question 20

What is hybridisation state of chiral C?

Answer 20

sp3

Question 21

If it is superimposable what it is?

Answer 21

Achiral

Question 22

if it is non-superimposable what it is?

Answer 22

Chiral

Question 23

What is the non-superimposable mirror image called?

Answer 23

Enantiomers

Question 24

What can a carbohydrate be?

Answer 24

D or L

Question 25

If the OH in a carbohydrate is to the left, what is it?

Answer 25

L

Question 26

If the OH in a carbohydrate is to the right, what is it?

Answer 26

D

Question 27

Can amino acids be D or L?

Answer 27

YES

Question 28

What are most amino acids in proteins?

Answer 28

L

Question 29

How do you determine of an amino acid is L or D?

Answer 29

Position of amine group

Question 30

How do you use Cahn-Ingold-Prelog naming system for chiral C?

Answer 30

Prioritise groups around C with lowest priority going away from you

Question 31

If Cahn-Ingold-Prelog naming system for chiral is clockwise order what do you name it?

Answer 31

R

Question 32

If Cahn-Ingold-Prelog naming system for chiral is anti-clockwise order what do you name it?

Answer 32

S

Question 33

What is the dashed line mean in drawing out chiral C?

Answer 33

Group is behind C

Question 34

What happens if priority 4 is at the front instead?

Answer 34

Viewing molecule from opposite side = reverse answer = clockwise really anti-clockwise

Question 35

What must we do if priority 4 is not at the back?

Answer 35

Must rotate molecule

Question 36

What do R + S isomers of a molecule have?

Answer 36

Identical physical + chemical properties

Question 37

How is plane polarised light produced?

Answer 37

By passing light through polarising filter

Question 38

What does each optically active compound have?

Answer 38

Character specific rotation

Question 39

What is a racemic mixture than contains equal amount of 2 enantiomers?

Answer 39

Optically inactive

Question 40

What is enantiomer excess (ee)?

Answer 40

Amount of enantiomer in excess of racemic mixture

Question 41

What happens if ee is 50%?

Answer 41

Then the observed rotation will only be 50% of the rotation of the pure enantiomer

Question 42

How can ee be calculated?

Answer 42

Observed specific rotation ---------------------------------------------------- X100 specific rotation of pure enantiomer

Question 43

What do R enantiomers do?

Answer 43

Bind correctly = trigger response

Question 44

What do S enantiomers do?

Answer 44

Cannot bind correctly = do not trigger response

Question 45

Describe Vigabatrin

Answer 45

S-enantiomer active as anti-convulsant Inhibits inactivation of GABA by GABA transaminase Increases levels of GABA = reduces seizures

Question 46

How do you name when more than 1 stereogenic centre?

Answer 46

Number the S + R centre

Question 47

What happens if the molecule has an internal plane of symmetry?

Answer 47

Meso compound