The fact that there are multiple nucleophilic substitution pathways is indicated by the observation that the rate of reaction depends on
The two main mechanisms for substitution at saturated carbon are referred to as SN2 and SN1.
the nature of the halogenoalkanes (primary, secondary, tertiary)
the reaction conditions (solvent and temperature)
the reaction conditions (solvent and temperature)
The two main mechanisms for substitution at saturated carbon are referred to as SN2 and SN1.
SN2 (Substitution, Nucleophilic, 2 means bimolecular)
For reactions proceeding by this mechanism, the rate depends on the concentration of both the nucleophile and the halide. This implies a single step process involving both of the reactants.
CH3CH2Br+–OH
CH3CH2OH + Br–
SN1 (Substitution, Nucleophilic, 1 means unimolecular)
For reactions proceeding by this mechanism, the rate depends on the concentration of one species (in this case the halide). Thus the mechanism must have more than one step, and the nucleophile is not involved in the step that determines the rate of the reaction.
(CH3)3CBr+–OH(CH3)3COH+Br–
For reactions proceeding by this mechanism, the rate depends on the concentration of both the nucleophile and the halide. This implies a single step process involving both of the reactants.
CH3CH2Br+–OH
CH3CH2OH + Br– SN1 (Substitution, Nucleophilic, 1 means unimolecular)
For reactions proceeding by this mechanism, the rate depends on the concentration of one species (in this case the halide). Thus the mechanism must have more than one step, and the nucleophile is not involved in the step that determines the rate of the reaction.
(CH3)3CBr+–OH
(CH3)3COH+Br–