we have seen that haloalkanes can undergo variety of reactions: sn2,sn1,e2,or e1. In principle, all these reactions compete with one another, and a variety of products are possible. When determining whether a reaction will proceed through an sn2,sn1,e2, or e1 mechanism, we must consider many factors. What is the nature of the electron pair donor? Is it a good nucleophile ? is it a sterong base?is it sterically hindered? What is the nature of the electrophile? Is it sterically hindered? And what about the solvent? Does it promote carbocation formation (sn1/e1 reactions)? Dose it increase or decrease the nucleophiliciity of the electron pair donor?