Question

Consider the following electrostatic potential diagrams:

Rank the compounds from lowest to highest boiling point, and explain your answer.

Short answer

Ethanol <Acetone<Propane

Acetone molecules contain polar CO double bonds, which cause dipole-dipole forces in between them. But hydrogen bonding is present in ethanol molecules. Since hydrogen bonding is stronger than dipole-dipole forces, ethanol has a higher boiling point.

The presence of the hydroxyl group leads to the presence of high molecular mass and strong hydrogen bonding. That’s why ethanol has a higher boiling point than Propane.

Acetone has a higher boiling point than Propane because the bonds present in Acetone are hard to break compared to that of Propane. The molecular weight of Acetone is also high compared to that of Propane.

Step-by-step solution

Electronegativity

As we all know, an electronegative atom such as fluorine, oxygen, or nitrogen is a hydrogen bond acceptor;it doesn’t matter whether it is bonded to a hydrogen atom.

Greater electronegativity of the hydrogen bond acceptor will create a stronger hydrogen bond.

Hydrogen bond

Hydrogen bonding acts between the molecules, which is a weak bond that usually acts in the presence of hydrogen in molecules.

A hydrogen bond has the electromagnetic attraction between polar molecules, where hydrogen is attached to the highly electronegative atom such as nitrogen, oxygen, or fluorine.

Explanation

Ethanol <Acetone<Propane

Acetone molecules contain polar CO double bonds, which cause dipole-dipole forces in between them. But hydrogen bonding is present in ethanol molecules. Since hydrogen bonding is stronger than dipole-dipole forces, ethanol has a higher boiling point.

Because of the presence of high molecular mass and strong hydrogen bonding because of the presence of the hydroxyl group, ethanol has a higher boiling point than Propane.

Acetone has a higher boiling point than Propane because the bonds present in Acetone are hard to break compared to that of Propane. The molecular weight of Acetone is also high compared to that of Propane.