1,2-Butanediol

1,2-butanediol structure

1,2-Butanediol, also known as 1,2-butylene glycol, is an organic compound (diol) with the formula HOCH2(HO)CHCH2CH3. It is a colorless, viscous liquid with a slight odor.

Table of Contents

1. Physical Properties of 1,2-Butanediol

1,2-Butanediol (CAS Number: 584-03-2) is a colorless liquid with numerous industrial applications. Here are some of its key physical properties:

Physical Properties of 1,2-Butanediol
Property Value
Chemical Formula C4H10O2
Molecular Weight 90.12 g/mol
Melting Point -50 °C
Boiling Point 195-196.9 °C (at 101.3 kPa)
Density (20°C) 1.0023 g/cm³
Refractive Index (20°C) 1.4382
Solubility in water Miscible in all proportions
Solubility in alcohols Readily soluble
Solubility in ethers and esters Slightly soluble
Solubility in hydrocarbons Insoluble
Dynamic Viscosity (20°C) 73 mPa·s
Flashpoint 107 °C

2. Chemical Properties of 1,2-Butanediol

1,2-Butanediol exhibits typical glycol reactivity like 2,3-butanediol, readily forming acetals and ketals. Additionally, it reacts with dicarboxylic acids or anhydrides to form polyesters, and with diisocyanates to form polyurethanes.

Reactions of 1,2-butanediol

The bacterium Gluconobacter oxydans DSM 2003 can efficiently produce (R)-2-hydroxybutyric acid (2-HBA) from 1,2-butanediol with high concentration (18.5 g/l) and good enantiomeric excess (99.7%).

3. Production of 1,2-Butanediol

1,2-Butanediol is synthesized by adding water to 1,2-epoxybutane. This exothermic hydration reaction (∆H = -93 kJ/mol) requires a 10- to 20-fold molar excess of water to prevent polyether formation.

Production of 1,2-butanediol by hydrolysis of 1,2-epoxybutane

Two primary production methods exist:

1. Without Catalyst: The reaction is carried out at 160-220°C and 10-30 bar, eliminating the need for a catalyst.

2. With Catalyst: Catalysts like sulfuric acid or strongly acidic ion exchange resins can be used. This allows the reaction to occur below 160°C and only slightly above atmospheric pressure.

Selectivity for 1,2-butanediol depends on the water excess, ranging from 70% to 92%. Higher ethers of 1,2-butanediol are formed as byproducts.

4. Uses of 1,2-Butanediol

While 1,2-butanediol has a modest range of direct applications, it is used as a solvent in the industrial process, as a chemical intermediate in the production of polymers and polyurethanes, and as a potential raw material for the synthesis of α-ketobutyric acid.

5. Toxicology

The median lethal dose (LD50) of 1,2-butanediol is 16 g/kg (rat, oral).

References