3.7 & 3.8 Optical Isomerism -- Aldehydes & Ketones Flashcards
(23 cards)
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
Y is a dialdehyde. Compound Z has empirical formula C3H4NO. Give structure of compound Z . Suggest reagent for freaction 3
This is nucleophilic addition
Formula of Y displayed at the top so you know where it is coming from
when reduction is occuring where NaBH4 is reagent what should you say name of mechanism is
Nucleophilic addition, not reduction
