Why is the boiling point of 2-propanol lower than 1-propanol

[Zayn]

Homework Statement

Why is the boiling point of 2-propanol lower than 1-propanol?

The Attempt at a Solution

Is this right?

Because 2-propanol has its hydroxyl group in the middle of the atom, the electrons are all moving to the centre of the atom as opposed to 1-propanol, which has the hydroxyl group to the side, moving the electrons towards one extreme of the molecule, causing it to act similarly to a magnet. Because 1-propanol has its hydroxyl to one side, the hydrogen bonds it forms can pack together more densely than with 2-propanol, requiring more kinetic energy (temperature) to break them apart, which translates to a higher boiling point.

 

[Borek]

in the middle of the atom, the electrons are all moving to the centre of the atom

You mean a molecule, don't you?

 

[kylec17]

That explanation is unnecessarily convoluted. It really just comes down to increased disperson and dipole-dipole forces.

Take a look at 1-propanol.
Now take a look at 2-propanol.

They both have hydrogen bonding, dipole-dipole, and disperson forces. The catch is that 1-propanol has higher surface area leading to increased disperson forces in comparison to the latter molecule. In addition, the net permanent dipole moment towards the oxygen is also higher due to the molecular geometry in the linear hydrocarbon (1-propanol). These increased dispersion forces lead to it being harder to pull molecules apart, thus raising the boiling point of said molecule.

For future reference: these questions are a process of deduction based on the strength of the intermolecular forces.

Hydrogen bonding > Dipole-dipole > Dispersion

Dispersion is a force that all molecules have, dipole-dipole is only in polar molecules, and hydrogen bonding is only present in molecules where hydrogen is directly bonded to oxygen, fluorine, or nitrogen.

Try answering the questions in those orders eliminating them as you go. If both molecules have the same types of forces, as in our example above, evaluate based on the relative strength of those forces.

edit: being able to pack closer together is surely a factor as well as mentioned in the explanation you gave