Final answer:
Alkyl amines are stronger bases than ammonia due to the presence of alkyl groups that increase the electron density on the nitrogen atom. This enhances the ability of amines to donate a lone pair and accept a proton. The inductive effect and hydrogen bonding also affect the base strength and physical properties of alkyl amines.
Step-by-step explanation:
Why Alkyl Amines Have Different Base Strengths Compared to Ammonia
Alkyl amines are organic bases similar to ammonia, but their basic strength differs due to structural variations. Ammonia (NH3) is a weak base because it has a lone pair of electrons on the nitrogen atom, capable of accepting a proton. Alkyl amines also possess this lone pair on their nitrogen atoms, allowing them to act as bases. However, the presence of alkyl groups (R groups) in alkyl amines increases the electron density around the nitrogen, enhancing their ability to donate the lone pair to accept a proton. As a result, alkyl amines are generally stronger bases than ammonia.
Moreover, the inductive effect of the alkyl group leads to a greater stabilization of the positive charge on the nitrogen atom when the amine becomes an ion, which is the organic counterpart of the ammonium (NH4*) ion. The primary and secondary amines can form hydrogen bonds, but less polar than those in alcohols, reflecting differences in their boiling points and solubility compared to other compounds such as alkanes and alcohols. With increasing chain length and molecular size, the solubility of amines in water decreases, further influencing their basic properties.