Final answer:
The reactions OH + Br- and H2O + CH2Br are classified as Sn2 due to the absence of indications of carbocation intermediates and because primary substrates support the one-step mechanism of Sn2. The reaction involving CH3CO2-Na+ is neither Sn1 nor Sn2 as it's not a substitution reaction.
Step-by-step explanation:
To classify the given reactions as Sn1 or Sn2, it's essential to understand the reaction mechanisms involved in nucleophilic substitution. The Sn1 reaction typically involves the formation of a stable carbocation intermediate and is unimolecular, meaning the rate of reaction is determined by the concentration of only one species, the substrate. This is often the case with tertiary substrates where steric hindrance and solvent effects aid in carbocation formation. On the other hand, the Sn2 reaction is bimolecular, involving the concerted action of two species (the nucleophile and the substrate) at the same time, leading to a transition state and then product formation. This mechanism often takes place with primary substrates and leads to an inversion of stereochemistry.
In the context of the student's question:
- a) OH + Br−: The substitution is likely Sn2 due to the absence of information suggesting carbocation stability or solvent effects.
- b) H2O + CH2Br: This reaction is Sn2 as water acts as a nucleophile, and the primary substrate suggests a one-step mechanism with inversion of stereochemistry.
- c) CH3CO2-Na+: It does not represent a nucleophilic substitution reaction.