Monocarbonyl

Monocarbonyl refers to compounds that contain exactly one carbonyl functional group (C=O) in their structure. This term distinguishes such molecules from those containing two or more carbonyl units (dicarbonyls and polycarbonyls). The carbonyl group is highly polar and largely governs the chemistry of monocarbonyl compounds.

Common examples span several functional classes. Aldehydes have the form R-CHO, including formaldehyde, acetaldehyde, and benzaldehyde. Ketones contain two carbon substituents on the carbonyl carbon, such as acetone and cyclohexanone. Other monocarbonyl families include carboxylic acids (R-COOH), esters (R-COOR'), amides (R-CONR'R''), and acyl chlorides (R-COCl). Each contains a single C=O group, even though the surrounding structure differs markedly, which influences reactivity and properties.

Reactivity and transformations: The carbonyl carbon is electrophilic, enabling nucleophilic additions and a wide range of condensations and rearrangements. Aldehydes are generally more reactive toward nucleophiles than ketones due to lower steric hindrance and less electron donation from substituents. Common transformations include nucleophilic addition, oxidation (aldehydes to carboxylic acids; certain ketones to diketones under strong conditions), and reductions to alcohols. Substituent effects modulate electrophilicity: electron-withdrawing groups increase susceptibility to attack; bulky groups can hinder it.

Applications: Monocarbonyl compounds are foundational building blocks in organic synthesis, pharmaceutical development, fragrances and flavors, and polymer chemistry (for example, esters and amides as intermediates). They are routinely analyzed by techniques such as infrared spectroscopy, which shows the characteristic C=O stretch near 1700 cm-1.