Question

Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
A. True
B. False

Answer 1

To solve this question, first we need to understand the chemical properties of aryl-amine. In case of aryl-amine, when the hydrogen atoms of the amino group are present in the primary aryl-amines are replaced by electron-donating alkyl groups and the basicity of the resultant aryl-amine increases. For example the basic character ${C_6}{H_5} - N{(C{H_3})_2} > {C_6}{H_5} - NH - C{H_3} > {C_6}{H_5} - N{H_2}$.

Complete step by step answer:

As we know that, when methylamine is added in water then it reacts with ferric chloride to form a precipitate i.e. hydrated ferric oxide. With the $+ I$ effect of the methyl group it makes methyl amine more basic in nature than water. Thus, methyl amine reacts with water to produce hydroxide ions.

Therefore, the chemical reaction of this will become:
$C{H_3} - N{H_2} + {H_2}O \to C{H_3} - N{H_3} + O{H^ - }$

The hydroxide ions produced in the reaction further react with ferric chloride to precipitate hydrated ferric oxide ($F{e_2}{O_3}.3{H_2}O$).
Now we can write the chemical equation for the above reaction as,
$2FeC{l_3} + 6OH \to F{e_2}{O_3}.3{H_2}O + 6C{l^ - }$
Therefore, the above statement is false (option B).

For better understanding we need to understand that when a chemical species with a tendency of releasing or donating electrons, such as an alkyl group. Then, it is introduced to a carbon chain. Here, the charge is relayed through the carbon chain and this effect is known as the positive inductive effect or the +I effect.

Additional notes:
In aryl amine, the hydrogen atom is replaced by an electron withdrawing group, the basicity of compound decreases. The order of basicity is given by,
${C_6}{H_5}N{H_2} > {({C_6}{H_5})_2}NH > {({C_6}{H_5})_3}N$

Note:
We need to note that,$+ I$ effect is observed among elements which have less electronegative atoms of the molecules with the release of electrons or by the electron donating groups. Usually, the alkyl groups are considered to be electron releasing or electron donating groups.