1,2-Dimethy1cyclohexene reacts with HBr in C CI_(4) to form mainly

1.	1,2-Dimethy1cyclohexene reacts with HBr in C CI_(4) to form mainly
Answer» `E-1-`bromo`-1,2-`dimethy`1`cyclohexene meso`-1-`bromo`-1,2-`dimethy`1`cyclohexane `(+-)Z-1-`bromo`-1,2-`dimethy`1`cyclohexane `(+-)E-1-`bromo`-1,2-`dimethy`1`cyclohexane Solution :Addition of hydrogen halide to an ALKENE in nonpolar solvents such as `C CI_(4)` is predominantly trans or anti on account of the formation of a bridged carbocation. This stereospecific reaction proceeds through a bridged cation like the bromonium ion wher `H` replaces `Br`. The intermediate may actually be a `pi` complex. In the absence of a solvent that can stabilize a free `R^(+),Br^(-)` attacks the protonated complex from the opposite face RESULTING in trans (anti) addition. Since water is a very good ion-solvator, THR protonated complex COLLAPSES to the free `R^(+)` thet can now recat FORM either face giving both cis and trans addition. Note: Both cis and trans addition occur with conc. aq. acid. With dilute aq. acid, addition of `H_(2)O` also occurs.

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