Question

Consider two amines and identify which is the stronger base in aqueous solution?

1) Ammonia (NH₃)
2) Methylamine (CH₃NH₂)
3) Ethylamine (C₂H₅NH₂)
4) Cannot be determined without additional information

Answer 1

Methylamine (CH3NH2) and dimethylamine ((CH3)2NH) are both stronger bases than ammonia due to electron-donating alkyl groups increasing electron density on the nitrogen. Dimethylamine is the stronger base compared to methylamine because it has two methyl groups. Consequently, the conjugate acid of methylamine (CH3NH3+) is stronger than that of dimethylamine ((CH3)2NH2+).

Step-by-step explanation:

To determine which is the stronger base between methylamine (CH3NH2) and dimethylamine ((CH3)2NH), we must understand that base strength is related to the tendency of the base to accept protons in solution. Methylamine has one methyl group (–CH3), which is electron-donating through inductive effect and hence increases the electron density on the nitrogen, making it more susceptible to protonation than ammonia (NH3).

Dimethylamine, with two methyl groups, has an even greater electron-donating effect due to the presence of two alkyl groups, making it a stronger base than methylamine. Therefore, (CH3)2NH is the stronger base. For the conjugate acids, (CH3)2NH2+ is the conjugate acid of (CH3)2NH, and CH3NH3+ is the conjugate acid of CH3NH2. Between these two, the conjugate acid formed from the stronger base would be the weaker acid, which in this case means CH3NH3+ is the stronger acid.