Topic 17: Organic II

Question 1

Optical isomers

Answer 1

Type of stereoisomerism (other type is geometric E-Z)
Non-superimposable mirror images formed by chiral molecules
Opposite optical activity
50-50 mixture of two optical isomers: racemic mixture

Question 2

Chiral molecules

Answer 2

Carbon bonded to 4 different GROUPS

Question 3

Optical Activity

Answer 3

Chiral molecules rotate plane polarised light
Different isomers rotate it in different directions
Racemic mixes have ni effect as rotation is countered by other half

Question 4

SN1

Answer 4

tertiary & secondary
trigonal planar carbocation formed
50-50 probability of nucleophile attack from above or below
So racemic mixture formed ALWAYS
if product does not interact with light: it is SN1

Question 5

SN2

Answer 5

primary and secondary
forms intermediate step with [] and …
STERIC HINDERANCE: nucleophile only attacks from one side (doesn’t fit in the other because halogen is too big) so 100% probability of backside attack
Forms one isomer only = optical activity

Question 6

Carbonyl compounds

Answer 6

C=O
Ketones & aldehydes
Permanent dipole-dipole interaction (O- to C+)
can hydrogen bond with water
Soluble in water (up to 5 carbons in chain)

Question 7

Nucleophilic addition

Answer 7

Reduction of aldehydes & ketones
Reducing agent LiAL4 (:H- radical and H+ ion) in DRY ETHER (Also works with cyanide )
acidified potassium sulfate
OH dative covalent bond
Aldehyde makes primary alcohol, ketone makes secondary