text: bimolecular elimination (e-2) synthesis of diphenylacetylene? im doing a e-2 synthesis of racemic stilbene dibromide to diphenylacetylene.  if the reactant is slightly impure with cis-stilbene would the product be impure even after recrystalization? the crystals were kind of brown and they were supose to be white.  i did an ir analysis and it showed some impurities but it was still diphenylacetylene.  my guess is that it would only effect the yield. i am assuming that the hope was to use only trans...this could effect your purity becuase in both trans and cis, you would have the same leaving group. this you would have different forms of the same product, one form might be brown..