Ring-opening reactions of epoxides can proceed by either S_(N)2 or S_(N)1 mechanisms, depending on the nature of the epoxide and on the reaction conditions. If the epoxide is asymmetric, the structure of the product will very according to which mechanisms dominates. When an symmetric epoxide undergoes solvolysis in basic methanol, ring-opening occurs by and S_(N)2 mechanisms, and the less subsitution carbon is the site of nucleophilic attack. Conversely, when solvolysis occurs in acidic methanol, the reaction occurs by a mechanisms with substantial S_(N)1 character, and the more substituted carbon is the site of attack. These are both good examples of regioselective reactions, examine the basic, S_(N)2 case first. The leaving group is an alkoxide anion, because there i s not acid avaialble to protonate the oxygen prior to ring opening. An alkoxide is a poor leaving group, and thus the ring is unlikely to open without a'push' from the nucleophile. Like in other S_(N)2 reactions, nucleophilic attack takes place from the backside, resulting in inversion t the electrophilic carbon. The best way to depict the acid-catalyzed epoxide ring-opening reaction is as a hybrid, or cross, between an S_(N)2 and S_(N)1 mechanism. First, the oxygen is protonated, creatinga good leaving group. Then the carbon-oxygen bond begins to break and positive charge begins to build up on the more substituted carbon. answer the following based on the above : The product formed after nucleophilic attack and mild hydrolysis is