Question

In each pair of compounds, select the stronger base, and explain your choice.
(a) HOCH₂NH₂and CH₃NH₂ (b) PhNH₂ and PhCH₂CH₂NH₂

(c)(d)

Short answer

(a)

CH₃NH₂ is more basic than OHCH₂NH₂

(b)

PhCH₂CH₂NH₂is more basic than PhNH_2.
(c)

(d)

Step-by-step solution

CH3NH2 is more basic than OHCH2NH2

CH₃NH₂ is more basic than OHCH₂NH₂because in the second one the OH group have electron withdrawing effect to takes electrons toward it and making less electrons nitrogen. So the second compound is less basic.

PhCH2CH2NH2 is more basic than PhNH2

PhCH₂CH₂NH₂is more basic than PhNH₂because in second structure there is a resonance contribution making the nitrogen less electrons available. So the first structurte[H2] is more basic thean the second.

Steric hinderence.

The cyclic compound is more basic because of lower steric hindrance.

Presence of extra methyl group in first structure.

In both structures the resonance makes less available of electrons. But in first structure the presence of methyl group makes the nitrogen lone pairs of electron more available. So first is more basic than the second.