Addition of Br2 to 2-pentene yields

[atlanta213]

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I know this reaction is going to be anti addition.

However on kaplan subject test, fishcer shows that 2bromo are on same side.
How this is possible?

I really have no idea how normal alkene form change to fischer form.

If you could explain anything about fishcer, I would greatly apprecaite your help.

Thanks

 

[TeamGuo]

Before you make the fischer projection, you react with Br2 and get the antiaddition.

But remember that alkanes= single bonds can rotate. That's why the on the fischer, 2 Br can be on the same side.

I would love to explain it to you but it's hard to explain without showing you via models. But the key is think 3D.

 

[wifi08]

obviously no one will be able to explain this clearly online you have to be shown how to do it. but ill just say that you are correct the Br add anti because of the bromonium ion intermediate. however the fisher doesnt project the exact orientation alone meaning you could rotate
the bonds without changing the molecule because after all the molecules are able to move around somewhat. but there are specific rules on how one can correctly rotate fisher projections which i will not get into