Nucleophilicity is a kinetic property. A higher nucleophilicity indicates that the nucleophile will easily donate its electrons to the electrophile and that the reaction will occur at the faster rate. The reaction rate also depends on the nature of the electrophile and solvent. Rank the following reactions from fastest to slowest based on the nucleophilicity of the nucleophile

[tex]\mathbf{(CH_3)_2N^- +CH_3 -Br \to (CH_3)_2NCH_3+Br^- \ }\\ \\ \\ \mathbf{CH_3NH^- +CH_3 -Br \to CH_3NHCH_3+Br^- \ } \\ \\ \\ \mathbf{H_3N^- +CH_3 -Br \to CH_3NH_2 + Br^- \ }[/tex]

What are Nucleophilic functional groups?

Nucleophilic functional groups include electron-rich atoms capable of donating an electron pair in order to establish a new chemical covalent bond. The most frequent nucleophilic functional groups are:

Water,
Alcohols,
Phenols,
Amines,
Thiols, etc

The protonation state of these functional groups has an effect on their nucleophilicity. Also, the trend of nucleophilicity goes from:

Tertiary,
Secondary,
Primary

The following reactions that we are supposed to find their order is given as follows:

[tex]\mathbf{CH_3NH^- +CH_3 -Br \to CH_3NHCH_3+Br^-} \\ \\ \\ \mathbf{(CH_3)_2N^- +CH_3 -Br \to (CH_3)_2NCH_3+Br^-} \\ \\ \\ \mathbf{H_3N^- +CH_3 -Br \to CH_3NH_2 + Br^-}[/tex]

From the fastest trend of the nucleophilicity of the nucleophile to the slowest, the correct arrangement is as follows:

[tex]\mathbf{(CH_3)_2N^- +CH_3 -Br \to (CH_3)_2NCH_3+Br^- \ \ \ ---(2'' \ ^0) \ \\}\\ \\ \\ \mathbf{CH_3NH^- +CH_3 -Br \to CH_3NHCH_3+Br^- \ \ \ \ ---(1^0) } \\ \\ \\ \mathbf{H_3N^- +CH_3 -Br \to CH_3NH_2 + Br^- \ \ \ --- \ \ \ \ (1^0)}[/tex]

The first reaction has two functional groups of methyl (-CH_3) attached to it which increases its nucleophilicity to the second one which has one methyl functional group attached to it.

Learn more about the Nucleophilic functional group here:
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