Propylene glycol
| Names | |
|---|---|
| IUPAC name
Propane-1,2-diol
| |
| Other names
α-Propylene glycol
1,2-Dihydroxypropane 1,2-Propanediol Methyl ethyl glycol (MEG) Methylethylene glycol | |
| Properties | |
| C3H8O2 | |
| Molar mass | 76.10 g/mol |
| Appearance | Colorless liquid |
| Odor | Odorless |
| Density | 1.036 g/cm3 |
| Melting point | −59 °C (−74 °F; 214 K) |
| Boiling point | 188.2 °C (370.8 °F; 461.3 K) |
| Miscibile | |
| Solubility | Miscible with acetone, chloroform, diethyl ether, ethanol, methanol |
| Vapor pressure | 0.05 mmHg at 20 °C |
| Acidity (pKa) | 14.8 |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Flash point | 103 °C (217.4 °F; 376 K) |
| Related compounds | |
| Related compounds
|
Ethylene glycol |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Propylene glycol, also called propane-1,2-diol or α-propylene glycol to differentiate it from its propane-1,3-diol isomer, is an organic compound with the chemical formula C3H8O2.
Contents
Properties
Chemical
Propylene glycol is metabolized in the human body to pyruvic acid.
Acid catalyzed dehydration of propylene glycol will give dimethyl dioxane.
Physical
Propylene glycol is a colorless viscous liquid, with a slight sweet taste and almost odorless. It is miscible with many solvents, such as water, methanol, ethanol, isopropanol, diethyl ether, acetone, chloroform. It melts at −59 °C and boils at 188.2 °C. Propylene glycol does not form azeotrope with water, meaning that it can be simply distilled from an aqueous mixture easily.
Availability
Propylene glycol is available as antifreeze, but one must read the label very carefully, as most antifreeze products contain ethylene glycol. Due to its low toxicity, propylene glycol can be purchased from certain food stores and chemical suppliers, in various grades.
Rum essence and vanilla extracts is a mixture of propylene glycol, water preservatives and flavors. The glycol can be extracted via drying and purification. Due to PG's high boiling point, vacuum distillation is recommended.
Preparation
Propylene glycol can be prepared by the hydrolysis of propylene oxide. However as propylene glycol is more available, it's much more cheaper to just buy it.
Projects
- Make propylene carbonate
Handling
Safety
Propylene glycol has a very low toxicity and has even been approved to be used in food products. It may cause irritations to some people however.
The biggest danger is the occasional confusion with ethylene glycol which is much more toxic (quite deadly) that its propylene counterpart, as both are sometimes called "glycol" for short, so it's best to read the label.
Storage
Propylene glycol should be stored in closed bottles, away from any fire source.
Disposal
Propylene glycol is nontoxic for the environment and can be safely burned.
