12.1B REACTION OF CARBONYL COMPOUNDS WITH NUCLEOPHILES
- One of the most important reactions of carbonyl compounds is the nucleophilic
addition to the carbonyl group.
- The carbonyl carbon bears a partial positive charge ⇒ the carbonyl group is
susceptible to nucleophilic attack.
- The electron pair of the nucleophile forms a bond to the carbonyl carbon atom.
- The carbonyl carbon can accept this electron pair because one pair of electrons
of the carbon-oxygen group double bond can shift out to the oxygen.
C O
δ−
O −
2) Carbanions form compounds such as RLi or RMgX.
δ+
Nu:− + Nu C
- The carbon atom undergoes a change in its geometry and its hybridization state
during the reaction.
- It goes from a trigonal planar geometry and sp^2 hybridization to a tetrahedral
geometry and sp^3 hybridization.
- The electron pair of the nucleophile forms a bond to the carbonyl carbon atom.
- Two important nucleophiles that add to carbonyl compounds:
- Hydride ions form compounds such as NaBH 4 or LiAlH 4.
- Oxidation of alcohols and reduction of carbonyl compounds:
R
H
O C O
[O]
oxidation
[H]
R C reduction
H
H
H
A primary alcohol An aldehyde
12.2 OXIDATION-REDUCTION REACTIONS IN ORGANIC
CHEMISTRY
