Question

Question #fcf69

Answer 1

Alkyl substituents are largely nonpolar, so the hydrogen bonding will happen with the amine group's hydrogen and the nitrogen's lone pair.

Remember that Hydrogen bonds form between an electronegative atom and a polar hydrogen.
In our case, the electronegative atom is the Nitrogen, thanks to its lone pair, and our polar hydrogen is a hydrogen bonded to another nitrogen atom.

See my figure below! (edit: figure updated)

Make sure you realize that the Carbon's hydrogens are nonpolar, and that the Nitrogen's lone pair will not interact with them (in terms of forming hydrogen bonding).

This is a result of the electronegativity of the atoms themselves as well as their electron bonding (methyl group is sp3 hybridized, while -NH2 is sp2 hybridized)

Hope that helps!