Chapter 8 Number 2

In this Sapling problem, 2-methyl bromopentane is reacting with ethoxide in an SN2 reaction. SN2 reactions cause the leaving group (Br) to be substituted by the nucleophile (ethoxide), leaving Br- and the new product. To start the problem, first the leaving group and nucleophile must be identified, which we've already done. SN2 mechanisms are also known to be concerted mechanisms, meaning that every part of the reaction occurs in one step. Then, since this is a concerted mechanism, ethoxide attacks the electrophilic carbon first which causes the bond between C--Br to break and form a new C--O bond. This leaves us with our new substituted product and Br- by itself with a full octet. In the problem, it is required that electron arrows are shown. So, first an arrow is drawn from the Oxygen in ethoxide to the electrophilic Carbon in 2-methyl bromopentane. Then another arrow is drawn from the bond between C and Br to Bromine causing the Bromine to be replaced by the ethoxide. Thus the new product is formed with a new ethoxide group added on. And voila, you have your SN2 reaction and products!