Question

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.

a. CH3NH- + CH3--Br → CH3NHCH3 + Br-

b. (CH3)2N- + CH3--Br → (CH3)2NCH3 + Br-

c. H2N- + CH3--Br → CH3NH2 +Br-

Answer 1

Based on the given information, we can rank the reactions from fastest to slowest based on the nucleophilicity of the nucleophile as follows:

1. b. (CH3)2N- + CH3--Br → (CH3)2NCH3 + Br- (This is because the lone pair on the nitrogen atom in (CH3)2N- is more available due to the presence of two methyl groups, which increases the electron density and makes it a stronger nucleophile.)
2. a. CH3NH- + CH3--Br → CH3NHCH3 + Br- (The nitrogen atom in CH3NH- is also a good nucleophile, but not as strong as the nitrogen atom in (CH3)2N-.)
3. c. H2N- + CH3--Br → CH3NH2 +Br- (The nitrogen atom in H2N- is a weaker nucleophile compared to the nitrogen atoms in (CH3)2N- and CH3NH-.)

It's worth noting that the reaction rate can also depend on the nature of the electrophile and solvent, as mentioned in the prompt, but since we don't have that information, we can only rank the reactions based on the nucleophilicity of the nucleophile.