Final answer:
Option A: Changing the solvent from CH₃OH to (CH₃)₂S=O in a substitution reaction would likely increase the rate because SN2 reactions favor polar aprotic solvents, which allow the nucleophile to be more reactive.
Step-by-step explanation:
The question addresses the effect of changing the solvent in a substitution reaction from methanol (CH₃OH) to dimethyl sulfoxide ((CH₃)₂SO). Considering the reaction CH₃(CH₂)₅Br + NaOH → CH₃(CH₂)5OH + Br⁻, where NaOH serves as the nucleophile, the correct answer would be that the rate would increase because SN2 reactions favor a polar aprotic solvent like dimethyl sulfoxide. This is because polar aprotic solvents stabilize the cation but do not solvate the anion as effectively as polar protic solvents, allowing the nucleophile (in this case, NaOH) to be more reactive. Therefore, changing the solvent to (CH₃)₂S=O would likely increase the rate of the substitution reaction.
Changing the solvent from CH₃OH to (CH₃)₂S=O can affect the rate of the substitution reaction. The reaction CH₃(CH₂)₅Br + NaOH → CH₃(CH₂)₅OH + Br⁻ is a nucleophilic substitution reaction of the SN2 type. SN2 reactions favor a polar aprotic solvent. CH₃OH is a polar protic solvent, while (CH₃)₂S=O is a polar aprotic solvent. Polar aprotic solvents are suitable for SN2 reactions as the nucleophiles are relatively free to approach the electrophilic carbon of the substrate. Therefore, the rate of the reaction would likely increase if the solvent is changed from CH₃OH to (CH₃)₂S=O.