Question

(i) Write $IUPAC$ name of $C{H_3}C{H_2}N{H_2}$.
(ii) Arrange the following amines in the order of their increasing basic strength in aqueous solution.
${\left( {C{H_3}} \right)_3}{N_1},\;{\left( {C{H_3}} \right)_2}N{H_1},\;C{H_3}N{H_2}$.

Answer 1

Amines are known to be the derivatives of ammonia which can be aliphatic or aromatic. Ammonia is known to be a weak base and thus the amines are also weakly basic in nature. There are various electron donating groups that are attached to amine in order to increase their basicity. To decrease the basicity of an amine, electron-withdrawing groups can make the same to occur.

Complete step by step answer:
(i): Ethylamine is the$IUPAC$ name of$C{H_3}C{H_2}N{H_2}$. It appears as a colourless liquid or a gas with an odour of ammonia. It is an aliphatic amine which is two-carbon and is a primary amine. It is a conjugate base of an ethylaminium. In $IUPAC$ base part of the name shows the carbon number which is present in the parent chain. In the naming, suffix is the functional group present on the main chain. The other parts that are attached to the parent chain are called substituents.

(ii) Alkyl substituted amines are known to be more basic in nature that the aryl amines. This is due to the electron density that becomes available due to the nitrogen atom and is distributed all around the aromatic ring.
- We know that to determine the basicity of a solution, the ${K_b}$ values are measured with the water reaction of the amine with us. The stronger the base is, the more ${K_b}$ value will be.
- The alternative for the same is $p{K_b}$. The more $p{K_b}$, the less strong the base is. Also, to determine the basicity of amines, the acidity of their conjugate acids must be found out. Any strong base has a weak conjugate acid and this the ${K_a}$ value becomes small and the $p{K_a}$ value becomes large

The order of their increasing basic strength in aqueous solution is ${(C{H_3})_3}{N_1} < C{H_3}N{H_2} < {(C{H_3})_2}N{H_1}$.

The following result is due to three major effects present. These are the inductive effect, solvation effect and steric effect. This is due to a combination of inductive effect, solvation effect and steric effect.

Note: The inductive effect is an electron donating effect. The solvation effect happens due to the presence of hydrogen bonding. In steric effect, the more the substituted group, the more steric hindrance is present. These effects are responsible for the difference in the basicity of both time of amines which is aliphatic and aromatic.