Chirality

Question 1

STEREOISOMERS

Answer 1

Different SPATIAL ARRANGEMENT of atoms

Question 2

CONSTITUTIONAL ISOMERS

Answer 2

Different CONNECTIVITY of atoms.

Question 3

ENANTIOMERS

Answer 3

stereoisomers: non-superimposable mirror images

Question 4

DIASTEREOMERS

Answer 4

stereoisomers: non-superimposable, not mirror images

Question 5

State main features of GEOMETRIC isomers

Answer 5

Z / CIS: SAME FACE
E / TRANS: OPPOSITE FACES

NO interconversion at body temp.

Question 6

CIP rules

Answer 6

Z- (priority 1 on SAME FACE of alkene)
E- (OPPOSITE FACE)

ASSIGN HIGHEST PRIORITY ATOMS

CLOCKWISE - R
ANTICLOCKWISE -S

Question 7

STEREOISOMERS are not interconvertable.

T or F?

Answer 7

T

ASYMMETRIC CENTRE

Question 8

OPTICALLY INACTIVE

Answer 8

ACHIRAL MOLECULES or RACEMIC MIXTURE

No net rotation of PPL

Question 9

RACEMIC MIXTURE

Answer 9

1:1 MIXTURE OF ENANTIOMERS

Question 10

CHIRALITY

Answer 10

NON-SUPERIMPOSABLE

ASYMMETRIC centre

Saturated C w 4 different groups

Question 11

ACHIRAL

Answer 11

SUPERIMPOSABLE

Question 12

ENANTIOMER

Answer 12

CHIRAL
NON-SUPERIMPOSABLE
MIRROR IMAGE

Question 13

DIASTEREOMERS

Answer 13

NON-SUPERIMPOSABLE, NON-MIRROR images

Question 14

Compare enantiomers & diastereomers

Answer 14

ENANTIOMERS have IDENTICAL physical & chemical properties

DIASTEREOMERS have DIFFERENT physical properties

Question 15

ERYTHRO vs THREO enantiomers

Answer 15

ERYTHRO: H on SAME SIDE of chain
THREO: H on OPPOSITE SIDES

Question 16

MESO compounds

Answer 16

ACHIRAL compound with CHIRAL centres
Internal plane of symmetry - SUPERIMPOSABLE MIRROR
OPTICALLY INACTIVE

Question 17

R enantiomers

Answer 17

Rotate PPL CLOCKWISE

(+) enantiomers

Question 18

S enantiomers

Answer 18

Rotate PPL ANTI-CLOCKWSIE

(-) enantiomers

Question 19

ENANTIOMERS have _____ physicochemical properties. EXCEPT:

Answer 19

IDENTICAL

EXCEPT:
ROTATION OF PPL
INTERACTION WITH OTHER CHIRAL MOLECULES

Question 20

How do ENANTIOMERS rotate PPL ?

Answer 20

OPPOSITE DIRECTIONS
by EQUAL AMOUNTS - racemate
unless enantiomerically favoured

Question 21

ROTATION OF PPL BY ENANTIOMERS

• DEXTROROTATORY
• LEVOROTATORY

Answer 21

(+) CLOCKWISE, d

(-) ANTICLOCKWISE, l

Question 22

ENANTIOMERIC EXCESS

Answer 22

Amount of pure enantiomer in XS of racemic mixture

Question 23

FISCHER PROJECTIONS

Answer 23

HORIZONTAL bonds (WEDGE) protrude (out of plane)
VERTICAL bonds (DASH) into plane

Question 24

MESO compounds

Answer 24

have an INTERNAL PLANE OF SYMMETRY

ACHIRAL compounds, with CHIRAL centres

SUPERIMPOSABLE

OPTICALLY INACTIVE

Question 25

2^n shows

Answer 25

maximum possible stereoisomers n = number of chiral centres

Question 26

Chiral compounds cannot have a plane of symmetry? T or F

Answer 26

T

Question 27

Separation of DIASTEREOMERS:

Answer 27

DIFFERENT SOLUBILITY in SOLVENTS | - CRYSTALLISATION

Question 28

Separation of ENANTIOMERS:

Answer 28

RESOLUTION: from racemic or enantiomerically enriched mixture by CRYSTALLISATION CHIRAL CHROMATOGRAPHY

Question 29

Describe RESOLUTION for separation of diastereoisomers

Answer 29

DIFFERENT SOLUBILITIES of diastereoisomeric salts allow for: CRYSTALLISATION of 1 diastereomer, evaporation of other RECOVERY of enantiomers by ACIDIFYING separated diastereoisomeric salts.

Question 30

Describe RESOLUTION by ESTERIFICATION

Answer 30

Covalent bond forms between chiral carboxylic acid & alcohol. Separate diastereomers by CRYSTALLISATION then RECOVER enantiomers by ESTER HYDROLYSIS.

Question 31

Why can diastereoisomers be separated?

Answer 31

On basis of DIFFERENT SOLUBILITIES.

Question 32

STEREOSELECTIVE reaction

Answer 32

PREFERENTIAL formation of one stereoisomer.

Question 33

STEREOSPECIFIC reaction

Answer 33

each stereoisomeric reactant produces a different stereoisomeric product or different mixture of products

Question 34

NO STEREOSELECTIVITY results in

Answer 34

RACEMIC MIXTURE

Question 35

CONCERTED REACTION

Answer 35

bond breaking & making occurs in SAME STEP E.g. SN2, E2 INVERTED or CONSERVED stereochemistry

Question 36

NON-CONCERTED reaction

Answer 36

Bond breaking & making in DIFFERENT STEPS. INTERMEDIATES formed - allow changes to stereochemistry E.g. SN1, E1 RACEMISATION occurs if intermediate forms

Question 37

State 3 types of constitutional isomers.

Answer 37

FUNCTIONAL, POSITION, SKELETAL (chain)

Question 38

State 2 categories & subtypes of STEREOISOMERS

Answer 38

GEOMETRIC | Molecules with chiral centres: ENANTIOMERS & DIASTEREOMERS