Question

Which molecule is expected to have the higher boiling point and why?

CH₃CH₂CH₂CH₂OH vs. CH₃CH₂CH₂CH₂CH₃

a. CH₃CH₂CH₂CH₂CH₃ because it has hydrogen bonding IMFs and CH₃CH₂CH₂CH₂OH does not have hydrogen bonding IMFs.
b.CH₃CH₂CH₂CH₂OH because it has London Dispersion IMFs and CH₃CH₂CH₂CH₂CH₃ does not have London Dispersion IMFs.
c.CH₃CH₂CH₂CH₂OH because it has hydrogen bonding IMFs and CH₃CH₂CH₂CH₂CH₃ does not have hydrogen bonding IMFs.
d.CH₃CH₂CH₂CH₂CH₃ because it has London Dispersion IMFs and CH₃CH₂CH₂CH₂OH does not have London Dispersion IMFs.

Answer 1

CH3CH2CH2CH2OH has a higher boiling point than CH3CH2CH2CH2CH3 because it can engage in hydrogen bonding intermolecular forces due to its -OH group, in addition to London dispersion forces, whereas the latter can only exhibit London dispersion forces.

Step-by-step explanation:

The higher boiling point is expected for the molecule CH3CH2CH2CH2OH over CH3CH2CH2CH2CH3.

The reason for the higher boiling point in CH3CH2CH2CH2OH is due to the presence of hydrogen bonding intermolecular forces (IMFs). This compound contains an -OH group, which allows for hydrogen bonding. Hydrogen bonding occurs when a hydrogen atom is directly bonded to a highly electronegative atom, such as oxygen, and this hydrogen atom is then attracted to the lone pair electrons on an oxygen atom in a nearby molecule.

Both molecules experience London dispersion forces, as all molecules do, but the ability of CH3CH2CH2CH2OH to also engage in hydrogen bonding results in much stronger intermolecular forces as compared to the exclusively dispersive forces in CH3CH2CH2CH2CH3. Consequently, more heat energy is required to overcome these forces, leading to a higher boiling point.