Aldehydes

Aldehydes are a class of organic compounds characterized by the presence of a carbonyl group (C=O) with the carbon atom also bonded to a hydrogen atom and an R group, which can be either a hydrogen atom or any generic alkyl or side chain. The general formula for an aldehyde is R-CHO.

Structure and Bonding

The carbonyl group in aldehydes consists of a carbon atom double-bonded to an oxygen atom. The carbon atom in the carbonyl group is sp2 hybridized, resulting in a planar structure with bond angles of approximately 120 degrees. The presence of the carbonyl group makes aldehydes polar compounds, with the oxygen atom being more electronegative than the carbon atom, leading to a partial negative charge on the oxygen and a partial positive charge on the carbon.

Nomenclature

Aldehydes are named by replacing the suffix "-e" of the parent alkane with "-al." For example, the simplest aldehyde, formaldehyde, has the formula H-CHO, and the next simplest, acetaldehyde, has the formula CH3-CHO. When the aldehyde group is attached to a ring, the suffix "-carbaldehyde" is used.

Synthesis

Aldehydes can be synthesized through several methods, including:

• Oxidation of primary alcohols.
• Ozonolysis of alkenes.
• Hydroformylation of alkenes.
• Friedel-Crafts acylation followed by reduction.

Reactions

Aldehydes are highly reactive and participate in a variety of chemical reactions, including:

• Nucleophilic addition reactions, such as the formation of hemiacetals and acetals.
• Oxidation to carboxylic acids.
• Reduction to primary alcohols.
• Condensation reactions, such as the Aldol reaction.

Applications

Aldehydes are used in a wide range of applications, including:

• As intermediates in the synthesis of pharmaceuticals and agrochemicals.
• In the production of perfumes and flavorings.
• As preservatives and disinfectants (e.g., formaldehyde).

Examples of Aldehydes

• Formaldehyde (H-CHO)
• Acetaldehyde (CH3-CHO)
• Benzaldehyde (C6H5-CHO)
• Glutaraldehyde (OHC-(CH2)3-CHO)

See Also

• Ketones
• Carboxylic acids
• Alcohols
• Organic chemistry