Glycerol vs Propylene glycol: what is the difference?
Glycerol has one more hydroxyl group than propylene glycol, making it thicker and a stronger humectant, while propylene glycol is the better flavour solvent.
One hydroxyl group apart.
Sources and notes
- The sentence under the titlefrom sourceMoleculeFinder comparison notesThe pair's answer line.
- The two drawingscomputedMoleculeFinder rule (RDKit MCS)Drawn the same way round on the skeleton they share; the amber marks where the two differ.
- The captionfrom sourceMoleculeFinder curated
- What is highlightedfrom sourceMoleculeFinder curatedOne line under each drawing, written from the atoms the amber marks.
- Structural similaritycomputedRDKit Morgan/Tanimoto0.46 of 1, a Morgan fingerprint Tanimoto coefficient. It measures shape, not effect.
Side by side
| Glycerol | Propylene glycol | |
|---|---|---|
| Molecular weightCalculated PubChem | 92.09 g/molC3H8O3 | 76.09 g/molC3H8O2 |
| Hydrogen-bond donorsCalculated PubChem | 3 | 2 |
| SweetnessMeasured Dermesonlouoglou et al. 2026 | 0.6× sugar | Not recorded |
| Against table sugar, which is 1. | ||
| Where each turns upEditorial MoleculeFinder food and product lists |
|
|
| FamilyEditorial MoleculeFinder curated | Sugar alcohols | Alcohols |
| Everyday groupEditorial MoleculeFinder curated | Food & flavor | Food & flavor |
| Chemical groupsCalculated Found by rule (RDKit) | Alcohols | Alcohols |
| Oral LD50Measured HSDB via PubChem | 5,570 mg/kgpure glycerol, rat, oral | 22,000 mg/kgpure propylene glycol, rat, oral |
| A single acute animal measure. It ranks nothing about human safety. | ||
Sources and notes
- Molecular weightcomputedPubChemComputed from the structure; the formula is under each weight.
- Hydrogen-bond donorscomputedPubChemThe hydrogens on nitrogen or oxygen that each molecule can lend to a hydrogen bond, counted from its structure.
- Sweetnessfrom sourceDermesonlouoglou et al. 2026
- Where each turns upfrom sourceMoleculeFinder food and product listsEach amount is an editorial figure from our lists, not a measurement of any one product. Each mark is set by hand on the list, never inferred.
- Familyfrom sourceMoleculeFinder curated
- Everyday groupfrom sourceMoleculeFinder curated
- Chemical groupscomputedFound by rule (RDKit)Each group is found in the structure by a chemical pattern.
- Oral LD50from sourceHSDB via PubChem
- Identifiersfrom sourcePubChemPubChem CID 753 (Glycerol) and 1030 (Propylene glycol).
In more detail
Both are viscous, sweet-tasting alcohols used to hold water in a product, C3H8O3 against C3H8O2. That extra group makes glycerol thicker and more strongly humectant, which is why it dominates in skincare, toothpaste and food glazes. Propylene glycol is thinner and a better solvent for flavour compounds, which is why it carries the flavour in e-liquid and in many oral medicines while glycerol supplies the visible vapour. Glycerol is also a real metabolic molecule: it is the backbone every triglyceride is built on, so the body has an established route for it. Both are widely permitted in food.
Sources and notes
- The paragraphfrom sourceMoleculeFinder comparison notes
Questions
- What is the difference between Glycerol and Propylene glycol?
- Glycerol has one more hydroxyl group than propylene glycol, making it thicker and a stronger humectant, while propylene glycol is the better flavour solvent.
- Is Glycerol bigger than Propylene glycol?
- Glycerol is the heavier molecule, 92.09 g/mol against 76.09 g/mol for Propylene glycol. Glycerol is C3H8O3 and Propylene glycol is C3H8O2.
- Which has the lower reported LD50, Glycerol or Propylene glycol?
- Glycerol, at 5,570 mg/kg (oral, rat), against 22,000 mg/kg (oral, rat) for Propylene glycol. An LD50 is one acute animal measurement, and the two here were not necessarily measured in the same species, so it is a data point rather than a ranking of how dangerous either is to a person.
Sources and notes
- The answersfrom sourceMoleculeFinderThe first is the pair's answer line; the others are read off the table above.