an E1cB mechanism. This transition state can be stabilized through induction or delocalization of the electron lone pair through resonance. In general it can be claimed that an electron withdrawing group on the substrate, a strong base, a poor leaving group and a polar solvent triggers the E1cB mechanism. An example of an E1cB mechanism that has a stable transition state can be seen in the degradation of ethiofencarb - a carbamate insecticide that has a relatively short half-life in earth's atmosphere. Upon deprotonation of the amine, the resulting amide is relatively stable because it is conjugated with the neighboring carbonyl. In addition to containing an acidic hydrogen on the β-carbon, a relatively poor leaving group is also necessary. A bad leaving group is necessary because a good leaving group will leave before the ionization of the molecule. As a result, the compound will likely proceed through an E2 pathway. Some examples of compounds that contain poor leaving groups and can undergo the E1cB mechanism are alcohols and fluoroalkanes. It has also been suggested that the E1cB mechanism is more common among alkenes eliminating to alkynes than from an alkane to alkene. One possible explanation for this is that the sp2 hybridization creates slightly more acidic protons. Although this mechanism is not limited to carbon-based eliminations. It has been observed with other heteroatoms, such as nitrogen in the elimination of a phenol derivative from ethiofencarb. Distinguishing E1cB-elimination reactions from E1- and E2-elimination reactions All elimination reactions involve the removal of two substituents from a pair of atoms in a compound. Alkene, alkynes, or similar heteroatom variations (such as carbonyl and cyano) will form. The E1cB mechanism is just one of three types of elimination reaction. The other two elimination reactions are E1 and E2 reactions. Although the mechanisms are similar, they vary in the timing of the deprotonation of the α-carbon and the loss of the leaving group. E1 stands for unimolecular elimination, and E2 stands for bimolecular elimination. In an E1 mechanism, the molecule contains a good leaving group that departs before deprotonation of the α-carbon. This results in the formation of a carbocation intermediate. The carbocation is then deprotonated resulting in the formation of a new pi bond. The molecule involved must also have a very good leaving group such as bromine or chlorine, and it should have a relatively less acidic α-carbon. In an E2-elimination reaction, both