Series
One, two, three hydroxyl groups give different alcohol classes.
Methanol is a monohydric alcohol, ethylene glycol a diol, and glycerol a triol.
Molecular compound · diol
Ethylene glycol
C₂H₆O₂
Ethylene glycol is C₂H₆O₂ with the structure HOCH₂–CH₂OH. It is a diol: two hydroxyl groups sit on a two-carbon chain.
Product distinction: antifreeze formulations can contain ethylene glycol, water and additives. The formulation is not the same thing as the pure compound.
Essentials
Two terminal –OH groups define the diol.
The structure HO–CH₂–CH₂–OH makes the two hydroxyl groups explicit and distinguishes ethylene glycol from compounds sharing the same atom counts but different connectivity.
Detail
The exact 2D structure is flexible around single bonds.
Both carbon atoms are tetrahedral in local geometry, and rotation about the C–C bond produces different conformations.
Conformation
The two –OH groups can approach or separate as bonds rotate.
Conformation affects intra- and intermolecular interaction possibilities.
Understand
Hydroxyl count changes intermolecular interaction capacity.
Comparing methanol, ethylene glycol and glycerol shows how additional –OH groups create more donor/acceptor sites while molecular size and geometry change too.
Water interactions
Ethylene glycol hydrogen-bonds strongly with water.
This contributes to high water affinity, but mixture properties also reflect non-ideal thermodynamics.
Reference identifiers
Names and identifiers that pin down the chemical identity.
| Formula | C₂H₆O₂ / HOCH₂CH₂OH |
|---|---|
| CAS Registry Number | 107-21-1 |
| PubChem CID | 174 |
Advanced
Push past the first model without losing the simple picture.
Why is ethylene glycol called a glycol?
Historically, glycol became a common name for ethane-1,2-diol and later for related diols.
Does two –OH groups mean twice the boiling point of methanol?
No. Bulk properties are emergent and do not scale linearly with functional-group count.
Is antifreeze pure ethylene glycol?
Usually no. Commercial antifreeze is a formulation with water and additives.
Constituent elements