1. Reactions of aldehydes and ketones
Prepared by:
Dr. Saima Najm
PhD Pharm Chem
Assistant Professor
L.C.P.S
2.
3. Since aldehydes contain a hydrogen atom bonded directly to
the carbonyl carbon, they can be oxidized to carboxylic acids.
1. Oxidation
4. Since ketones have no hydrogen atom bonded to the carbonyl
group, they are not oxidized under similar reaction conditions.
5. Aldehydes can be oxidized selectively in the presence of other
functional groups using silver(I) oxide (Ag2O) in aqueous
ammonium hydroxide (NH4OH). This is called Tollens reagent.
Only aldehydes react with Tollens reagent; all other functional
groups are inert.
Oxidation with Tollens reagent provides a distinct color change
because the Ag+ reagent is converted to silver metal (Ag),
which precipitates out of the reaction mixture as a silver
mirror.
2. Silver mirror test
6. In the addition reaction, new groups X and Y are added to
the carbonyl group of the starting material.
One bond of the double bond is broken and two new
single bonds are formed.
3. Addition
11. Addition of one molecule of alcohol (ROH) to an aldehyde or
ketone forms a hemiacetal.
Like other addition reactions, one bond of the C=O is broken
and two new single bonds are formed.
Acyclic hemiacetals are unstable; they react with a second
molecule of alcohol to form acetals.
12. Two examples of acetal formation using ethanol
(CH3CH2OH) as the alcohol component are given.
