What are SN1, SN2, E1, E2, and the various substitutions (e.g. nucleophilic and electrophilic aromatic substitutions) and additions, and how are their mechanisms related to one another?

Answer 1

This is a whole lecture but the basic summary is that E1/E2 reactions will form an alkene, while Sn1/Sn2 will substitute one atom to another(hence the name, substitution reaction). Sn1 and E1 reactions are capable of hydrogen/methyl shifting because they have a carbocation intermediate. They are also 2 step reactions while Sn2 and E2 are 1 step reactions. In terms of what products you'll get, Sn1 reactions yield racemic products (equal proportion of both the R and S configuration). Sn2 will yield a complete inversion of whatever you're substituting. For example if your starting material is on a wedge, the Sn2 reaction will create a dashed product. One of the most common E1 reactions that a lot of students tend to forget are dehydration reactions, where a hydroxyl group forms a double bond in the presence of an acid and heat.

Answer 2

This is a whole lecture but the basic summary is that E1/E2 reactions will form an alkene, while Sn1/Sn2 will substitute one atom to another(hence the name, substitution reaction). Sn1 and E1 reactions are capable of hydrogen/methyl shifting because they have a carbocation intermediate. They are also 2 step reactions while Sn2 and E2 are 1 step reactions. In terms of what products you'll get, Sn1 reactions yield racemic products (equal proportion of both the R and S configuration). Sn2 will yield a complete inversion of whatever you're substituting. For example if your starting material is on a wedge, the Sn2 reaction will create a dashed product. One of the most common E1 reactions that a lot of students tend to forget are dehydration reactions, where a hydroxyl group forms a double bond in the presence of an acid and heat.