Nomenclature and Structure of Carbonyl Group
This section focuses on the carbonyl group (>C=O), which is a pivotal functional group in organic chemistry. Carbonyl compounds are classified into aldehydes, ketones, and carboxylic acids.
Nomenclature
Two systems exist for naming these compounds:
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Common Naming: Aldehydes typically derive their names from the corresponding carboxylic acids by dropping the '-ic' and adding 'aldehyde'. Ketones are named by combining alkyl or aryl groups adjacent to the carbonyl group.
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IUPAC Naming: Aldehydes are named by replacing the '-e' from the corresponding alkane with '-al', while ketones change '-e' to '-one'. For cyclic compounds, numbering starts from the carbonyl group.
Structure
The carbonyl carbon is sp² hybridized, forming three sigma bonds: two with adjacent carbon or hydrogen atoms and one with oxygen. The fourth electron forms a pi bond with oxygen, giving a planar structure with bond angles around 120°. The polar nature of the carbonyl group renders carbonyl compounds electrophilic.
Importance
Aldehydes, ketones, and carboxylic acids are ubiquitous in nature and have numerous applications in pharmaceuticals, food flavorings, solvents, and materials. Their polar characteristics significantly impact their physical properties and reactivities.
This understanding lays the groundwork for exploring the reactions of carbonyl compounds and correlating their structures to functions in organic synthesis.