| Factor | SN1 | SN2 |
| (1) Number of steps | Two steps | One step |
| (2) Molecularity/Order | Unimolecular/1st order | Bimolecular/2nd order |
| (3) Reaction rate | Depends upon concentration of one reacting species | Depends upon concentration of two reacting species |
| (4) Attack of a nucleophile | Back side attack and front side attack on a substrate with equal probability | Only back side attack on a substrate |
| (5) Transition state | Two steps, two transition states | One step, one transition state |
| (6) Type of substrate | Mainly tertiary (3°) substrate | Mainly primary (1°) substrate |
| (7) Stereochemistry | 50% inversion and 50% retention of configuration | 100% inversion of configuration |
| (8) Enantiomer | Forms racemic mixture | Forms opposite enantiomer |
| (9) Solvent | Polar solvent favourable | Nonpolar solvent favourable |
| (10) Energy of activation | Two values of energies of activation | One value of energy activation |
| (11) Intermediate | Carbocation intermediates | No intermediate |
| (12) Nucleophile | Weak nucleophile favourable | Strong nucleophile favourable |
| (13) Order of reactivity in alkyl halides | Tertiary > Secondary > Primary | Primary > Secondry > Tertiary |
