Definition

1. Noun:
   • The univalent unsaturated organic radical C₃H₅; derived from propylene: In chemistry, the "allyl radical" refers to a specific, highly reactive molecular fragment with the chemical formula C₃H₅. It is characterized by a three-carbon chain with a double bond between two of the carbons and an unpaired electron on the terminal carbon, making it a free radical. It is formally derived by removing a hydrogen atom from propylene (also called propene).

Examples of Usage

• Noun:
  • The stability of the allyl radical is due to resonance delocalization of the unpaired electron.
  • In this reaction mechanism, an allyl radical is formed as a key intermediate.
  • The chemist studied the reactivity of the allyl radical with various substrates.

Advanced Usage

• "Allylic position": This term describes the carbon atom adjacent to a carbon-carbon double bond in a molecule. The allyl radical is the simplest radical species centered at such a position.
  • Hydrogen atoms in an allylic position are more easily abstracted to form radicals.

Variants and Related Words

• Allyl group (or allyl): (n) The functional group with the structure H₂C=CH–CH₂–. Unlike the radical, it is not a free radical but a substituent that can be part of a larger molecule (e.g., allyl alcohol, CH₂=CHCH₂OH).
• Allylic: (adj) Pertaining to or characteristic of an allyl group or the allyl radical.
  • Allylic bromination is a common organic reaction.

Synonyms

• 2-Propenyl radical: A systematic name for the same chemical species.
• CH₂=CH–CH₂•: A common structural representation, where the dot (•) signifies the unpaired electron.

Related Phrases/Concepts

• Radical intermediate: The allyl radical is a classic example of a reactive intermediate in free-radical chemical reactions.
• Resonance stabilization: A key concept explaining the relative stability of the allyl radical; the unpaired electron is delocalized over two carbon atoms.

Noun

1. the univalent unsaturated organic radical C3H5; derived from propylene