Saved Bookmarks
| 1. |
When benzene is treated with DCl at low temperatures a compound C_(6)H_(6)DCl, is formed. On warming the reactants, C_(6)H_(6) and DCl are re-formed. However, in the presence of AlCl_(3) an isomer of C_(6)H_(6)DCl is produced, which on warming, gives mainly C_(6)H_(5)D and HCl. Explain. |
| Answer» Solution :Since D is not incorporated into the BENZENE I ring in the absence of `AlCl_(3)` isomer C has no C-D `sigma` bond. Instead, the D end of DC is attracted to the `pi` cloud of benzene to form a loosely BOUND `pi` complex, indicated by an arrow in the structural formula. `pi` complexes are also called charge -transfer complexes, because the electron-rich benzene ring,t he donor molecule transfers some electron density to the electron-poor D of DCl, ACCEPTOR molecule. wit the catalyst `AlCl_(3)`, exchange of `D^(+)` for `H^(+)` occurs o WARMING. this exhange requires the formation of a C-D bond to give the `sigma` complex. with `D^(+)`. the benzene ring is reformed by losing an H rather than the D because the C-H bond is weaker than the C-D bond. | |