Question

Among $i-BuNH_2, NH_3, Me_2NH, EtNH_2,$ the number of compound(s) more basic than $MeNH_2$ is/are ______.

Answer 1

Correct Answer: 3

To determine the number of compounds more basic than $MeNH_2$ (methylamine), we need to understand the basicity of the amines. The basicity of amines is influenced by the following factors:

• Alkyl Substitution: Alkyl groups are electron-donating and stabilize the positive charge on the nitrogen when the amine donates a pair of electrons, increasing basicity.
• Steric Hindrance: Larger groups can hinder the approach of the proton and reduce basicity.

Now, let's evaluate each given compound:

1. $i-BuNH_2$ (Isobutylamine): Has an electron-donating isobutyl group. Typically more basic than $MeNH_2$ due to greater electron donation.
2. $NH_3$ (Ammonia): Has no alkyl groups, making it generally less basic than alkylamines like $MeNH_2$.
3. $Me_2NH$ (Dimethylamine): Contains two methyl groups; more electron-donating capacity than $MeNH_2$, thus more basic.
4. $EtNH_2$ (Ethylamine): Similar to $MeNH_2$ but with a slightly larger alkyl group; typically more basic than $MeNH_2$.

From this analysis, $i-BuNH_2$, $Me_2NH$, and $EtNH_2$ are all more basic than $MeNH_2$. Therefore, the number of compounds more basic than $MeNH_2$ is 3. This value falls within the given range (3,3).

Conclusion: 3 compounds are more basic than $MeNH_2$.