3.7 & 3.8 Optical Isomerism -- Aldehydes & Ketones Flashcards
What is an enantiomer
Another word for optical isomer
What is a chiral carbon and state two other names for it
a carbon atom bonded to 4 different groups
- stereogenic centre
- asymmetric carbon
What is meant by enantiomerically pure
Only one optical isomer present
What is a racemic mixture
- state another term for it
An equal mixture of enantiomers
What can aldehydes and ketones be reduced to
- aldehydes can be reduced back to primary alcohols
- ketones can be reduced back to secondary alcohols
State for reduction of aldehydes and ketones :
* name of mechanism
* reagent
* nucleophile
* condition
- Nucleophilic addition
- reagent : NaBH4
- nucleophile = H^-
- condition : acidic solvent
Draw mechanism of reduction of propanal propan-1-ol
The first H^- (one at middle/bottom left) can be replaced by CN^- (which has a lone pair) but nuclephile is still H^-
Why can nucleophilic addition to aldehydes and asymmetrical ketones result in a racemic mixture of optical isomers
C=O bond is planar
this means there is a 50:50 chance of the nucleophile attacking from either side
this results in equal amounts of each isomer forming, and so a racemic mixture is formed
A racemic mixture is not optically active as the different isomers rotate the plane of polarised light equally and hence cancel out
Isooctane is 2,2,4 - trimethylpentane
What do you class as an assymetric carbon
A chiral carbon
Name mechanism between HCN and propanal
State reagents and conditions
Name product formed
Nucleophilic addition
Reagent : HCN
Condition : aqueous and room temperatur
State observation when water reacts with CH3COCl
Steamy fumes : HCl
Reaction for when carbonyl bond formed from OH
OXIDATION
