A level – Elimination – E2 Stereoselective for E alkenes

Click the structures and reaction arrows in sequence to view the 3D models and animations respectively

In this elimination reaction, a new double bond is formed when the carbon – bromine bond breaks at the same time as the OH removes the H+. The elimination takes place from the anti-periplanar conformation, as this is the most stable conformation.

As you can see from the reaction above, when 2-bromobutane undergoes an elimination reaction, two possible stereoisomers are formed. This is because 2-bromobutane has two conformations with H and Br anti-periplanar, but the one that is less hindered forms the major product, so the E-alkene predominates.

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