In methanol (a polar protic solvent), the correct order of nucleophilicity of the halide ions towards $CH X_{3} Br$ is

A $F X^{-} > Cl X^{-} > Br X^{-} > I X^{-}$
B $I X^{-} > Br X^{-} > Cl X^{-} > F X^{-}$
C $Br X^{-} > I X^{-} > Cl X^{-} > F X^{-}$
D $Cl X^{-} > Br X^{-} > I X^{-} > F X^{-}$

Answer: B

In protic solvents small anions are strongly hydrogen bonded, so the small fluoride is held most tightly and is least nucleophilic. The large, polarisable iodide is least solvated and most nucleophilic. The order is

I X^{-} > Br X^{-} > Cl X^{-} > F X^{-}

Practice Organic Reaction Mechanisms III: Nucleophilic Substitution More on SN1 vs SN2: substrate, nucleophile, solvent, leaving group

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In methanol (a polar protic solvent), the correct order of nucleophilicity of the halide ions towards CHX3​Br is

Answer: B

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In methanol (a polar protic solvent), the correct order of nucleophilicity of the halide ions towards $CH X_{3} Br$ is