Propanediol

Overview

Propanediol refers to any of the three isomeric chemical compounds with the formula C₃H₈O₂. These compounds are types of diol, which means they contain two hydroxyl groups (−OH). The most commonly discussed isomer is 1,2-propanediol, also known as propylene glycol.

Isomers

Propanediol has three isomers:

• 1,2-Propanediol (propylene glycol): This is the most widely used isomer in industrial and consumer products. It is a colorless, viscous liquid that is miscible with water, acetone, and chloroform. It is used as a solvent, in the production of polymers, and as a food additive.

• 1,3-Propanediol: This isomer is used in the production of polytrimethylene terephthalate (PTT), a type of polyester. It is also used as a solvent and in the synthesis of other chemicals.

• 2,2-Propanediol (also known as pinacol): This isomer is less common and is primarily used in organic synthesis.

Chemical Properties

Propanediols are characterized by their two hydroxyl groups, which make them alcohols. These hydroxyl groups allow propanediols to participate in hydrogen bonding, which affects their boiling points and solubility in water.

Physical Properties

• Molecular formula: C₃H₈O₂
• Molar mass: 76.09 g/mol
• Density: Varies by isomer, but generally around 1.036 g/cm³ for 1,2-propanediol
• Boiling point: 188.2 °C for 1,2-propanediol

Applications

Propanediols are used in a variety of applications due to their chemical properties:

• 1,2-Propanediol:

 * Used as a humectant in food and cosmetics.
 * Serves as a carrier fluid in hydraulic systems.
 * Acts as a de-icing fluid for aircraft.
 * Used in the production of polyester resins.

• 1,3-Propanediol:

 * Used in the production of PTT fibers, which are used in textiles and carpets.
 * Acts as a building block in the synthesis of polyurethanes.

Safety and Environmental Impact

Propanediols are generally considered to be of low toxicity. However, exposure to large amounts can cause irritation and other health effects. 1,2-Propanediol is recognized as safe for use in food and cosmetics by various regulatory agencies.

Also see

• Diol
• Polyethylene glycol
• Ethylene glycol
• Polypropylene glycol

External links

• Propylene glycol on Wikipedia
• 1,2-Propanediol on PubChem