I'm trying to figure out the isomeric products of the radical monobromination of bicyclo[2.2.1] heptane. I'm not sure at which site the bromination would happen and what makes one site better than the other (how can one determine this without given the reaction enthalpy ?). I was also given the hint that there are stereoisomers but I can't think of one.

  • $\begingroup$ Would help the discussion if you supplied a drawing with atom numbering $\endgroup$
    – Waylander
    Commented Jul 17, 2019 at 13:27

1 Answer 1


The radical monobromination of bicyclo[2.2.1] heptane could give $\ce{1}$ ,$\ce{2}$ and $\ce{3}$.

However , $\ce{2}$ and $\ce{3}$ , are unstable .On observing $\ce{2}$ , planar radical at bridgehead is unstable due to angular strain introduced by planarity of radical at bridgehead .

Similarly in $\ce{3}$ , due to angular strain introduced in to the neighboring bonds,this radical also is unstable.

The situation leads to product from ${1}$ , that gives stereoisomers as shown below.

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