The most common is called an SN2 reaction. It is a simple nucleophilic attack of a nucleophile onto an electrophilic carbon. This attack causes and inversion of absolute configuration of the carbon center.
- SN2 Nucleophilic Substitution causes inversion of configuration: (best in polar aprotic solvents, strong nucleophiles and good leaving groups.)
Going from (R) to (S)
If Carbon is tertiary and nucleophile is weak then it undergoes SN1 reaction: j has same products as SN2 but is racemised and best in polar protic solvent and the reaction is 1st order, not 2nd...
-racemization is when there is the absolute configuration of the carbon center is not either retained or inverted but rather randomized.
-1st order means it takes place in one rate limiting step, as opposed to the SN2 and E2 which you will learn about next, which have 2 steps.
Another type of reaction is an elimination reaction. In an elimination reaction, instead of substitute the leaving group with a nucleophile, it is removed and a double bond is formed in the compound.
Stuff in favor of SN2 over E2: Low temperature; Modest bases, nucloephiles; Sterically small bases; Primary is best, tertiary is worst
E1 reactions occur under similiar conditions to the S1 reaction, but instead of having substitution, elimination occurs. E1 vs SN1: both are good with weak nucleophiles and polar protic solvents; both want a good leaving group; tertiary substrates; if SN1, then E1 present too; these two reactions are always competing.