HELP CHEM

1.
Butylamine is a stronger base than ammonia.
Bu-NH2 + H+ ≒ Bu-NH3+
H-NH2 + H+ ≒ H-NH3+
Butyl group is electron releasing which would stabilize the Nu-NH3+ ion by inductive effect (to disperse the positive charge).

Phenylamine is a weaker base than ammonia.
Ph-NH2 + H+ ≒ Ph-NH3+
H-NH2 + H+ ≒ H-NH3+
In phenylamine, the lone pair of electrons on the N atom participates the delocalization of π electrons above and below the benzene ring. Therefore, the lone pair of electrons on the N atom is less available to accept a proton (H+). Besides, if it accepts a proton to become Ph-NH3+, it loses stabilization energy.


2.
Amines are rather soluble in water, because amine molecules form hydrogen bonds with water molecules.

Amines are more soluble in dilute hydrochloric acid than in water. This is because amines are basic which would accept protons to become ammonium ions, which are ionic and more soluble in water.
e.g. R-NH2 + H+ → R-NH3+ (ionic, more soluble in water).


3.
At a temperature below 4oC, dissolve separately the primary alkylamine and the primary arylamine into hydrochloric acid, and then add sodium nitrate(III) crystals to dissolve in the solution.

The primary alkylamine gives colourless bubbles of nitrogen. This is because the diazonium ions are unstable which would then react with water to give nitrogen gas.
R-NH2 + NaNO2 + dilute HCl → [R-N2+] (unstable below 4oC)
[R-N2+] + H2O → ROH + H+ + N2

The primary arylamine gives no observable change (no bubbles are formed). This is because the diazonium ions formed are stable below 4oC.
Ar-NH2 + NaNO2 + dilute HCl → Ar-N2+ (stable below 4oC)
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