Chemistery

Let's compare E1 and E2 in the following aspects: Base Substrate Solvent Leaving Group Kinetics Stereochemistry Rearrangements  Base E1: As the base abstracts the proton only after the carbocation intermediate is formed, it does not affect the rate of reaction, hence not important. E2: A strong base is indeed needed to promote the one-step reaction. Substrate E1: A more substituted substrate stabilizes the carbocation intermediate.  E2: A more substituted substrate forms a more substituted alkene.  Solvent E1: A polarizing solvent enhances the rate of ionization as it pulls the cation and anion apart.  E2: The transition state is less sensitive to the solvent as the transition state has its negative charge shared over the whole molecule.  Leaving Group Both reactions need a good leaving group.  Kinetics E1: The rate is only determined by the substrate as it is the only molecule that ionizes. E2: Both the substrate and the base aff...

Knowing the reactions is not enough, we have to take a step further: to organize and compare them. There are several aspects that we can compare for the nucleophilic substitution reactions: Nucleophile Substrate Solvent Leaving Group Kinetics Stereochemistry Rearrangements 1. Nucleophile SN1 : Since a nucleophile is not involved in the rate-determining step, it does not have to be a strong nucelophile (in fact, a strong nucleophile will prefer a SN2 over SN1). SN2 : A strong nucleophile is required to make the concerted reaction feasible. 2. Substrate SN1 : As a carbocation intermediate determines the rate of reaction, a more substitued substrate is needed. SN2 : A crowded substrate will hindered the electrophilic carbon from the attack of the nucleophile. So a bulky substrate is a bad substrate for SN2. 3. Solvent SN1 : The ionization step is rate-determining, so a highly polar (ionizing) protic solvent stabilizes the ions formed. SN2 : It needs energy to strip ...