• Presentation
  • Reactions
  • Contact
  • Addition reactions
    • Simple addition
    • Oxidative addition
    • Addition with insertion
    • Addition with elimination
  • Substitution reactions
    • Dissociative mechanism
    • Associative mechanism
    • Exchange mechanism
  • Double sustitution or exchange reactions
    • Halide exchange mechanism
    • Exchange mechanism in other compounds
  • Rearrangement or isomerization reactions
    • Isomerization mechanisms in compounds of representative elements
    • Isomerization mechanisms in coordination compounds
  • Proton transfer reactions
    • Proton transfer in compounds of representative elements
    • Proton transfer in compounds of transition elements
  • Electron transfer reactions
    • Proton transfer in compounds of representative elements
    • Proton transfer in compounds of transition elements

Exchange mechanism in halide compounds

Molecular halides EXn can act as Lewis acids through E or as Lewis bases through the terminal halogen atoms. Therefore, two different halide E'Ym and EXn can form short life dimers with halogen bridges, that can dissociate into different monomers. The process ultimately leads to a redistribution of the halogen atoms X and Y between two atoms, E and E ', generating the most stable mixture of products possible. The reaction may also occur between a halide and a compound of hydrogen (H/X exchange). See examples.

Examples

BF3 + BCl3 ⇄ BF2Cl + BFCl2

SiCl4 + H-F ⇄ SiFCl3 + H-Cl

BF3 + BCl3 ⇄ BF2Cl + BFCl2

BF3 + BCl3 ⇄ BF2Cl + BFCl2

This reaction occurs through a binuclear species with double halogen bridge.

SiCl4 + H-F ⇄ SiFCl3 + H-Cl

This reaction is an example of synthesis of fluoride from other halides compounds. The likely mechanism begins with the addition of HF to SiCl4. In this scheme it is assumed that the mechanism involves a state of transition of four centers in which the formation of the Si-F and H-Cl and the breakage of the Si-Cl and H-F bonds are concerted. If there is no perfect synchrony and dominates the approach of hydrogen form HF, the first addition would be close to a proton transfer.