 Therefore, to interpret this reaction, it is important to look at the transition state, which resembles the concerted rate limiting step.In the "Depiction of SN2 Reaction" figure, the nucleophile forms a new bond to the carbon, while the halide (L) bond is broken.An E1 reaction consists of an unimolecular elimination, where the rate determining step of the mechanism depends on the removal of a single molecular species.