(i) Loss of proton from amines gives alkyl amide ion whereas loss of a proton from alcohol gives an alkoxide ion.
`underset("Amine")(RNH_2) to underset("Alkylamide")(RNH^(-)) + H^(+)`
`underset("Alcohol")(ROH) to underset("Alkoxide ion")(RO^(-)) + H^+`
Since O is more electronegative than `N_1` therefore , `RO^(-)` can accommodate the -ve charge more easily `RNH^(-)` . Consequently , `RO^(-)` is more stable than `RNH^(-)` . Thus, alcohols are more acidic than amines.
(ii) Primary amines `(RNH_2)` have two hydrogen atoms on the N atom and therefore, form intermolecular hydrogen bonding.
Tertiary amines `(R_3N)` do not have hyrogen atoms on the N atom and therefore, these do not form hydrogen bonds. As a result of hydrogen bonding in primary amines, they have higher boiling points than tertiary amines of comparable molecular mass. For example, b.p. of n-butylamine is 351 K while that of tert-butylamine is 319 K.
(iii) Both arylamines and alkyamines are basic in nature due to the presence of lone pair of N-atom . But arylamines are less basic than alkylamines . For example, aniline is less basic than ethylamine as shown by `K_b` values :
Ethylamine : `K_b = 4.7xx10^(-4)`
Aniline : `K_b = 4.2xx10^(-10)`
The less basic character of aniline can be explained on the basic of aromatic ring present in aniline. Aniline can have the following resonating structures :
It is clear from the above resonating strucutures that three of these (III, IV and V) acquire some positive charge on N atom. As a result, the pair of electrons become less avilable for protonation . hence, aniline is less basic than ethyl amine in which there is no such resonance.
