hydroxyl

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hydroxyl

A chemist draws a hydroxyl group on the whiteboard.

Definition

Noun: A functional group in chemistry consisting of one oxygen atom covalently bonded to one hydrogen atom, represented by the formula -OH. It is a characteristic component of bases (like hydroxides), many acids (like carboxylic acids), and alcohols.

Usage

The term "hydroxyl" is used specifically to refer to the -OH group when it is considered as a substituent or a functional unit within a molecule. It is a core concept in organic and inorganic chemistry.

Examples
  • The hydroxyl group is responsible for the solubility of alcohols in water.
  • In a water molecule, the oxygen atom is bonded to two hydrogen atoms, so it is not a hydroxyl group; a hydroxyl is specifically an -OH unit bonded to another atom.
  • Carboxylic acids contain a carbonyl group (C=O) and a hydroxyl group (-OH) on the same carbon atom.
Advanced Usage
  • Hydroxyl Radical: A highly reactive, neutral speciesOH) with an unpaired electron. This is distinct from the hydroxyl group and is a major reactive oxygen species in atmospheric chemistry and biology.
  • Hydroxyl Ion: Refers to the hydroxide anion (OH⁻), which is the hydroxyl group carrying a negative charge. This is the species present in basic solutions.
Variants and Related Words
  • Hydroxy-: A prefix used in systematic chemical names to indicate the presence of a hydroxyl group. (e.g., 2-hydroxypropanoic acid).
  • Hydroxide: A compound containing the hydroxide ion (OH⁻), typically ionic, like sodium hydroxide (NaOH).
  • Hydroxylase: An enzyme that catalyzes the introduction of a hydroxyl group into a substrate.
Synonyms
  • -OH group: The direct structural synonym.
  • Hydroxy group: An alternative name, often used interchangeably.
Related Phrases / Concepts
  • Hydrogen Bonding: The hydroxyl group can participate in hydrogen bonding, which significantly affects the physical properties (e.g., boiling point, solubility) of molecules that contain it.
  • Functional Group: The hydroxyl group is a primary example of a functional group, which determines the characteristic chemical reactions of a molecule.
hydroxyl

A chemist draws a hydroxyl group on the whiteboard.

Noun
  1. the monovalent group -OH in such compounds as bases and some acids and alcohols