[kriggy]

Hi there,
In my notes its written that in Se2 mechanism there is no inversion of configuration (ie. stays same) why is that? I was thinking that the the mechanism is that the electrophile comes from the other side of the leaving group just like in Sn2. Is my understanding wrong?

[TheUnassuming]

As I understand it, with Se2 you can have front and back attack depending on the exact reactants ect. 

http://www.scribd.com/doc/25905271/Aliphatic-Electrophilic-Substitution-Reactions#scribd

[kriggy]

Thanks a lot, that picture on page 1 explains it pretty well 

[swintarka]

Sorry to write unasked, but is this mechanism really needed? Is't it also described in terms of nucleophilic substitution, but from a point of view of the other reagent?

[TheUnassuming]

Is't it also described in terms of nucleophilic substitution, but from a point of view of the other reagent?

Se2 is distinctly different from SN2, although they look similar in a way when drawn, the electrons are behaving differently which is what allows for fun things like Se2 from the front!