CarbonioOH

CarbonioOH is a term occasionally used to denote the hydroxy-bearing carbon atom in organic molecules, i.e., the carbon to which a hydroxyl group is attached. In structural notation, this center is represented as C–OH, and in many contexts it marks the defining feature of alcohols. The carbon that carries the hydroxyl group in an alcohol is sometimes called the carbinol carbon; it can be primary, secondary, or tertiary depending on how many carbon substituents surround it.

In general chemistry, the hydroxy group defines the alcohol class. The presence of −OH confers polarity and enables hydrogen bonding, which raises boiling points and often enhances water solubility for smaller molecules. Alcohols tend to be less water-soluble as their carbon skeleton grows, due to increasing hydrophobic character.

Reactivity at the carbon–oxygen center centers on transformations of the C–OH bond. Alcohols can be oxidized to aldehydes or ketones and, with strong oxidants, to carboxylic acids. They can be converted into alkyl halides, tosylates, or esters through substitution or condensation reactions. Dehydration of alcohols yields alkenes, typically under acidic catalysis.

Common examples include methanol (CH3OH), ethanol (CH3CH2OH), isopropanol (CH3CHOHCH3), and tert-butanol ((CH3)3COH). These substances illustrate how the hydroxy-bearing carbon underpins a wide range of chemical behavior characteristic of alcohols.

See also: alcohol, hydroxyl group, carbinol.