# E1 elimination and alkyne formation

Are E1 elimination reactions possible from a trans dihalide alkane (like 1,2-dibromoethane) all the way to the alkyne (like acetylene)? Or is only E2 possible from the alkene to alkyne? What is the rate of reaction?

My thoughts are that E1 is a possible reaction to form the alkyne, with E2 taking place if there are any anti peri-planar hydrogens and a strong base. So, another question might be that which of these has the faster rate of reaction - an E1 reaction or an E2 reaction with anti periplanar hydrogens that are only available through conformational energies and torsional strain?

• What is the proposed E1 intermediate? Do you have any idea if this is a high-energy intermediate? – Lighthart Mar 3 '16 at 19:17

Yes, in your example, it is possible to form acetylene. E1 mechanism does not depend on whether the leaving group is anti to $\ce{H}$ or not.