27Ea - Organic Chemistry (Mcmurry)

Question

What product (s) would you expect to obtain from reaction of 1,3-cyclohexadiene with each of the following?

(a) 1 mol ${\mathbf{Br}}_2$in${\mathbf{CH}}_2{\mathbf{Cl}}_2$

Step-by-Step Solution

Answer

Reaction of 1,3-cyclohexadiene with 1 mol of Br 2 in CH 2 Cl 2

1,3 cyclohexadiene is a an unsaturated six member ring where two conjugated double bonds are present. When conventional alkenes undergo halogenation (chlorination and bromination), vicinal di halides (halogen atoms on adjacent carbon atoms) are obtained. But dienes react differently with halogens (${\text{Br}}_{\text{2}}$). Reaction of 1,3-cyclohexadiene with 1 mol of  ${\text{Br}}_{\text{2}}$ in ${\text{CH}}_{\text{2}}{\text{Cl}}_{\text{2}}$ gives to isomeric products (dibromo derivatives).

                                                              Reaction

Explanation

The reason for the formation of two isomeric products is that,  the carbocation formed during the reaction is resonance stablised, leading to the formtation of two products. 

                                                             Reaction