Lesson 5: Functional groups

Alcohols

Section 2 of 5

An alcohol has an -⁠OH group joined to a carbon atom. Alcohol names end in -⁠ol.

Methanol, CH₃OHOne carbon atom bonded to three hydrogen atoms and to an oxygen atom that carries a hydrogen atom, an -OH group.HHCOHH
Methanol, CH₃OH: one carbon with an -⁠OH group.
Ethanol, C₂H₅OHTwo carbon atoms in a chain; the second carbon is bonded to an oxygen atom that carries a hydrogen atom, an -OH group.HHHCCOHHH
Ethanol, C₂H₅OH: two carbons with an -⁠OH group.

The name works the same way as for alkanes: meth- for 1 carbon, eth- for 2, prop- for 3, then -⁠ol for the -⁠OH group. Methanol, ethanol, propanol.

The -⁠OH group is a lot like part of a water molecule, H–O–H. That is why small alcohols such as ethanol mix with water so easily, while alkanes like octane float on top of it.

Ethanol, C₂H₅OHTwo carbon atoms in a chain; the second carbon is bonded to an oxygen atom that carries a hydrogen atom, an -OH group.OH
Ethanol as a skeletal formula: a two-carbon line ending in OH.

Quick check

What does the name propanol tell you about the molecule?