Stereospecific Reactions

Stereospecific Reactions are chemical reactions where a specific stereoisomer of the reactant always leads to a specific stereoisomer of the product.

Definition of Stereospecific Reactions:

• A stereospecific reaction is one where the stereochemistry of the reactant completely determines the stereochemistry of the product.
  • Each stereoisomeric reactant leads to a different stereoisomeric product.
  • The reaction mechanism is such that it requires specific spatial arrangements of atoms.

Key Characteristics:

• The reaction is not just selective, it is deterministic: different stereoisomers of the reactant give distinct products.
• Only one product is formed from a given stereoisomer of the starting material.

Example:

Bromination of 2-Butene

• When 2-butene is treated with Br₂, the reaction proceeds via an anti-addition mechanism, and the stereochemistry of the alkene determines the stereochemistry of the dibromide product.
• Reactions:
  1. Cis-2-butene + Br₂ → Produces a racemic mixture of enantiomers:
     • (S,S)-2,3-dibromobutane
     • (R,R)-2,3-dibromobutane
     • 
  2. Trans-2-butene + Br₂ → Produces only the meso form:
     • meso-2,3-dibromobutane
     • 

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