Reactions of Aldehydes & Ketones

Oxidation of Aldehydes

• aldehydes can be oxidized to carboxylic acids by   * chromic acid   * $Tollen’s Reagent$ is made of silver ion, ammonia, and hydroxide ion     * this reaction can also be called the $silver mirror test$ or $Tollen’s test$

Example with Chromic Acid

Example with Tollen’s Reagent

Formation of Hemiacetals & Acetals with Alcohols

Formation of Hemiacetals

• aldehydes/ketones and hemiacetals exist in equilibrium when dissolved in an alcohol
• the reaction to form a hemiacetal is an example of an addition reaction

Formation of Acetals

• aldehydes/ketones can be formed into acetals in the presence of   * an acid catalyst   * excess of alcohol
• this reaction results in the loss of a water molecule
• the aldehyde/ketone actually reacts with 2 molecules of the alcohol

Hydrolysis of Acetals

• $Hydrolysis reaction$: a reaction where water breaks the bonds in a compound
• The hydrolysis of an acetal is the reverse reaction of acetal formation
• This is a reversible reaction and is controlled by the amounts of reactants used

Reduction of Aldehydes to Alcohols

• This reaction can be done using one of two agents   * Sodium borohydride   * Lithium aluminum hydride (LAH)     * also reduces carboxylic acids, esters, and amides