Imagine that a scientist mixes bromomethane and potassium iodide in methanol. Gi
ID: 587581 • Letter: I
Question
Imagine that a scientist mixes bromomethane and potassium iodide in methanol. Given these reactants and conditions, what reaction type (or types) is/are likely to occur? Remember to consider the type of alkyl halide that is involved, and remember also to consider whether the anion will act predominantly as a base or as a nucleophile or as both a base and a nucleophile. If the latter, consider the figure below to guide your decision. Finally, remember to consider the pKa rule, as it applies to each of the various reaction archetypes. SN2 E2 2° Type of Alkyl Halide 1° 3° predominantly SN1 O predominantly E2 mostly Sy2 with some E2 predominantly E1cB O mostly E2 with some SN2 O mostly SN1 with some E1 O predominantly SN2 mostly E1 with some SN1 O predominantly E1Explanation / Answer
Bromomethane is primary halide. It will predominantly undergoes SN2 type reaction.In protic polar solvent like Methanol I- ion is a better nucleophile and weaker base. Thus the I- ion in polar solvent is more polarisable and readily available for making bonds to carbon in the SN2 transition state. Again bromide ion is a good leaving group.for a favourable reaction difference of pka values between nucleophile and leaving group is large. Here basicity between bromide and iodine ion is favours the SN2 reaction in forward direction.