I'll break it down
Sn1
- 3*>2*>1*
- Prefer polar protic solvents (water,methanol, etc)
- Only dependent on the LG (not the nucleophile)
- Formation of carbocation intermediate
- Because it forms carbocation intermediate, Nu can attack from top or bottom, so you get racemic mixtures (thus you have optical inactivity)
- Achiral intermediate
E1
- Pretty much same as everything stated for Sn1
- Hard to really differentiate between E1 products and Sn1 products although kaplan says E1 preferred at higher temperatures
Sn2
- 1*>2*>3*
- Prefer polar aprotic solvents (DMSO, etc) (lack acidic hydrogens)
- Bimolecular, so dependent on LG and Nu
- Inversion of products because of backside attack by Nu (basically it switches config. S becomes R or R becomes S)
- Product is optically active
- Best Nu are basic atoms
E2
- Easier to differentiate between Sn2 and E2
- E2 is not sterically hindered like Sn2 so it can attack tertiary carbons as long as you have a STRONG BASE
- So if you see a strong base and a tertiary alkyl halide think E2.
that's all i can think of for now. maybe if you tell me what kind of problems you're having trouble with, i can be of more help.
