Question

Which of the following must be overcome during the boiling of acetonitrile, CH₃CN?

1. Dispersion forces
2. Dipole-dipole forces
3. Hydrogen bonds

a) 1, 2, and 3
b) 1 and 2
c) 1 only
d) 1 and 3
e) 2 only

Answer 1

Dispersion forces and dipole-dipole forces must be overcome during the boiling of acetonitrile, CH₃CN, which means the correct answer is (b) 1 and 2.

Step-by-step explanation:

During the boiling of acetonitrile, CH3CN, the intermolecular forces that must be overcome are dispersion forces and dipole-dipole forces. Although C-H bonds are polar, they are only minimally polar and do not lead to hydrogen bonding in acetonitrile; therefore, the correct answer is (b) 1 and 2. Acetonitrile has a cyano group (—C≡N), which can engage in dipole-dipole interactions due to the electronegativity difference between the carbon and nitrogen atoms.

The dispersion forces, which are present in all molecules, also contribute to the intermolecular forces in acetonitrile. However, acetonitrile cannot form hydrogen bonds because it lacks a hydrogen atom bonded directly to an electronegative atom like nitrogen, oxygen, or fluorine.