Carbonyl compounds

Carbonyl Compounds

Carbonyl compounds are a class of organic compounds characterized by the presence of a carbonyl group (C=O). This functional group is one of the most important in organic chemistry due to its reactivity and presence in a wide variety of chemical structures, including aldehydes, ketones, carboxylic acids, esters, and amides.

Structure and Bonding

The carbonyl group consists of a carbon atom double-bonded to an oxygen atom. The carbon atom is sp² hybridized, resulting in a planar structure with bond angles of approximately 120 degrees. The double bond consists of a sigma (σ) bond and a pi (π) bond. The oxygen atom is more electronegative than the carbon atom, creating a polar bond with a partial positive charge on the carbon and a partial negative charge on the oxygen.

Types of Carbonyl Compounds

Aldehydes

Aldehydes have the general formula RCHO, where R is a hydrogen atom or a hydrocarbon group. The carbonyl group in aldehydes is bonded to at least one hydrogen atom. Common examples include formaldehyde (HCHO) and acetaldehyde (CH₃CHO).

Ketones

Ketones have the general formula RCOR', where R and R' are hydrocarbon groups. The carbonyl group in ketones is bonded to two carbon atoms. A well-known example is acetone (CH₃COCH₃).

Carboxylic Acids

Carboxylic acids contain the carboxyl group (-COOH), which is a carbonyl group bonded to a hydroxyl group. They have the general formula RCOOH. Acetic acid (CH₃COOH) is a common carboxylic acid.

Esters

Esters are derived from carboxylic acids and have the general formula RCOOR'. They are formed by the reaction of a carboxylic acid with an alcohol. Ethyl acetate (CH₃COOCH₂CH₃) is a typical ester.

Amides

Amides have the general formula RCONR'₂, where R and R' can be hydrogen or hydrocarbon groups. They are formed by the reaction of a carboxylic acid with an amine. An example is acetamide (CH₃CONH₂).

Reactions of Carbonyl Compounds

Carbonyl compounds undergo a variety of chemical reactions due to the electrophilic nature of the carbonyl carbon.

Nucleophilic Addition

Aldehydes and ketones commonly undergo nucleophilic addition reactions. A nucleophile attacks the electrophilic carbonyl carbon, leading to the formation of an alcohol. An example is the addition of hydrogen cyanide (HCN) to form cyanohydrins.

Oxidation

Aldehydes can be oxidized to carboxylic acids using oxidizing agents such as potassium permanganate (KMnO₄) or chromic acid (H₂CrO₄). Ketones are generally resistant to oxidation.

Reduction

Carbonyl compounds can be reduced to alcohols. Aldehydes are reduced to primary alcohols, while ketones are reduced to secondary alcohols. Common reducing agents include sodium borohydride (NaBH₄) and lithium aluminum hydride (LiAlH₄).

Applications

Carbonyl compounds are widely used in the chemical industry. Aldehydes and ketones are important intermediates in the synthesis of pharmaceuticals, fragrances, and dyes. Carboxylic acids and their derivatives are used in the production of polymers, solvents, and food additives.

See Also

• Aldehyde
• Ketone
• Carboxylic acid
• Ester
• Amide

References

• Smith, J. G. (2016). Organic Chemistry. McGraw-Hill Education.
• Carey, F. A., & Giuliano, R. M. (2016). Organic Chemistry. McGraw-Hill Education.