Carbonyl Compounds: Aldehydes and Ketones

Carbonyl Compounds

• Aldehydes and ketones contain a carbonyl group (C=O).
• The carbonyl carbon has two remaining bonds occupied by hydrogen, alkyl, or aryl substituents.
• Aldehydes have at least one hydrogen substituent (RCHO or RCH=O).
• Ketones have no hydrogen substituents (RCOR`).

Aldehydes

• Aldehydes are named using common names derived from the corresponding carboxylic acid.
• The ‘oic acid’ ending is replaced with ‘aldehyde’.
• The aldehyde group is always terminal.
• Substituent locations are indicated using Greek letters (α, β, γ, δ, ε, ω) starting from the α-carbon (next to the carbonyl carbon).
• Aromatic aldehydes are often named as derivatives of benzaldehyde.

IUPAC Nomenclature of Aldehydes

• The longest continuous carbon chain containing the C=O group is identified.
• The ending -e is replaced with -al.
• The CHO group is assigned the number “1” position, taking precedence over other functional groups.
• If CHO is bonded to a ring, the ring is named, and the suffix -carbaldehyde is added.

Ketones

• Ketones are named using common names by listing alkyl substituents on the carbonyl group alphabetically followed by "ketone".
• Substituent positions are indicated using Greek letters starting from the α-carbon.
• IUPAC names are derived by finding the longest chain containing the carbonyl group.
• The -e ending of the parent alkane is changed to -one.
• The carbonyl carbon receives the lower number.
• Ketone groups are named as 'oxo' substituents in aldehydes.

Preparation of Aldehydes

• Aldehydes can be prepared through various methods, including oxidation of primary alcohols, reduction of acid chlorides, and ozonolysis of alkenes.

Preparation of Ketones

• Ketones can be prepared through various methods, including hydration of alkynes, oxidation of secondary alcohols, and Friedel-Crafts acylation.

Reactions of Aldehydes

• Aldehydes undergo oxidation to carboxylic acids using oxidizing agents like potassium dichromate.
• Tollens' reagent can be used to distinguish aldehydes from ketones.
• Aldehydes are reduced to primary alcohols using reducing agents like sodium borohydride.

Reactions of Ketones

• Ketones resist oxidation by most oxidizing agents.
• Ketones are reduced to secondary alcohols using reducing agents like sodium borohydride.