3.8 Aldehydes and Ketones Flashcards
What shape is the carbonyl group in aldehydes and ketones?
It is planar
What is the mechanism for the reduction of aldehydes and ketones?
Nucleophilic addition
What is a source of hydride and hydrogen ions?
Sodium borohydride
NaBH4
Describe the reduction of propanone through nucleophilic addition to form propan-2-ol.
1) An arrow is drawn from the lone pair on a hydride ion is to the delta+ on a carbon in the carbonyl group. An arrow is drawn from the double C=O bond to the O
2) A negative intermediate is formed with the hydrogen now bonded to the carbon and the O having a lone pair and negative charge. An arrow is drawn from this lone pair to the hydrogen ion.
3) Propan-2-ol is formed.
What is the proportion on enantiomers formed from nucleophilic addition and why?
A racemic mixture is formed, as the carbonyl group can be attacked from either behind or in front, meaning that naturally a 50-50 split is made. This means that 50% are +enantiomers and 50% are -enantiomers
