Final answer:
The predominant intermolecular force in (CH3)2NH is hydrogen bonding, a strong type of dipole-dipole interaction that occurs due to the presence of highly electronegative nitrogen atoms.
Step-by-step explanation:
The predominant intermolecular force in (CH3)2NH is hydrogen bonding. This is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to a highly electronegative atom such as nitrogen (N). In (CH3)2NH, the hydrogen atoms attached to the nitrogen can form hydrogen bonds with the nitrogen atoms of adjacent molecules because nitrogen is one of the three most electronegative elements capable of forming hydrogen bonds, along with oxygen (O) and fluorine (F). While London dispersion forces are also present, they are generally weaker than hydrogen bonds and are not the predominant force in this compound.