hemiacetal

Thân thiện

A chemist draws the structure of a hemiacetal on a whiteboard.

Definition

1. Noun:
   • An organic compound: A hemiacetal is a specific type of organic molecule characterized by a carbon atom bonded to both an alkoxy group (-OR) and a hydroxy group (-OH), where the same carbon atom is also bonded to a hydrogen atom and another organic group (often an alkyl or aryl group). It is typically formed as an intermediate in the chemical reaction between an aldehyde or a ketone and an alcohol.

Usage Examples

• Noun:
  • The formation of a hemiacetal is a key step in the mechanism of sugar cyclization, such as when glucose forms a ring structure.
  • In the laboratory, the hemiacetal intermediate is often unstable and quickly reacts further to form a more stable acetal.
  • The chemist identified the compound as a hemiacetal based on its characteristic infrared spectroscopy signal.

Advanced Usage

• "Cyclic hemiacetal": A hemiacetal where the alkoxy and hydroxy groups are part of the same molecule, forming a ring. This structure is fundamental to carbohydrate chemistry.
  • Fructose readily forms a five-membered cyclic hemiacetal.

Variants and Related Words

• Acetal (n): A related, more stable compound formed from a hemiacetal in a reaction with a second alcohol molecule.
• Hemiketal (n): A closely related compound formed from a ketone instead of an aldehyde. (Note: In modern IUPAC nomenclature, the term "hemiacetal" is often used generically for both types.)

Synonyms

• None commonly used: "Hemiacetal" is a precise technical term in organic chemistry with no direct common-language synonyms. Descriptive phrases like "aldehyde-alcohol addition product" may convey a similar idea in specific contexts.

Related Phrases

• Hemiacetal formation: The chemical process of creating a hemiacetal.
  • Hemiacetal formation is a reversible, acid-catalyzed reaction.

Related Idioms

• Not applicable: As a specialized scientific term, "hemiacetal" is not used in idiomatic expressions.

Học thuật

Noun

1. an organic compound usually formed as an intermediate product in the preparation of acetals from aldehydes or ketones