Explain why methanethiol has a lower BP than methanol even though methanethiol has a higher molecular weight?

Question

methanethiol has a BP of 6C while methanol has 65C.

Answer 1

Being more electronegative, O forms stronger H-bonds than does S. So it takes more energy to break the extended network.

Answer 2

Oxygen is more elctronegative than sulphur. It makes O-H more polar than S-H bond. There will be stronger intermolecular hydrogen bonding in methanol than methanethiol.

For similar reason H2O has higher boiling point htan H2S. H2O is a high boiling liquid while H2S is a gas.