The boiling point of a compound is determined by the strength of the intermolecular forces between its molecules. The stronger the intermolecular forces, the higher the boiling point. Here's why CH3OH (methanol) boils higher than CH3SH (methanethiol):

* Hydrogen Bonding in Methanol (CH3OH): Methanol has a hydrogen atom bonded to an oxygen atom (O-H). This allows for hydrogen bonding, a strong intermolecular force that arises from the attraction between a partially positive hydrogen atom and a partially negative oxygen atom on adjacent molecules.

* Dipole-Dipole Interactions in Methanethiol (CH3SH): Methanethiol has a sulfur atom bonded to a hydrogen atom (S-H). While the S-H bond is polar, it's less polar than the O-H bond in methanol. Therefore, methanethiol experiences weaker dipole-dipole interactions.

* London Dispersion Forces: Both methanol and methanethiol experience London dispersion forces, which are weak intermolecular forces arising from temporary fluctuations in electron distribution. However, these forces are generally weaker than hydrogen bonding or dipole-dipole interactions.

In summary: Methanol's strong hydrogen bonding interactions are significantly stronger than the weaker dipole-dipole interactions in methanethiol. These stronger intermolecular forces in methanol require more energy to overcome, resulting in a higher boiling point.