In the presence of lithium or aluminum amide bases, epoxides may open to give the corresponding allylic alcohols. Removal of a proton adjacent to the epoxide, elimination, and neutralization of the resulting alkoxide lead to synthetically useful allylic alcohol products. In reactions of chiral, non-racemic epoxides, the configuration of the allylic alcohol product matches that of the epoxide substrate at the carbon whose C–O bond does not break (the starred carbon below). Besides β-elimination some other reactions are possible, as metalation of the epoxide ring can take place competitively. Vinylogous eliminations are possible when the epoxide substrate is substituted with vinyl or dienyl groups. Unconstrained systems tend to form trans double bonds, as significant non-bonding interactions are avoided in the transition state for the formation of trans products (see equation (2) below). The strongly basic conditions required for most isomerizations of this type represent the reaction's primary disadvantage.