What Is 2-Methyl-1-Propanol (Isobutanol)?
2-Methyl-1-propanol, commonly known as isobutanol or isobutyl alcohol, is an organic compound with the molecular formula C4H10O and a CAS number of 78-83-1. It is a colorless liquid with a characteristic sweet, slightly pungent odor. Isobutanol is one of the four structural isomers of butanol and is widely used as a solvent, chemical intermediate, and fuel additive.
Chemical Structure and Isomer Relationships
Isobutanol belongs to the class of primary alcohols, with the general structure R-CH2OH. Its molecule consists of a branched carbon skeleton: a central carbon atom bonded to two methyl groups, one hydrogen atom, and a CH2OH group, written as (CH3)2CHCH2OH. This branched structure distinguishes isobutanol from the straight-chain n-butanol and from the secondary and tertiary isomers, sec-butanol and tert-butanol, and it explains the differences in boiling point, density, and reactivity among the butanol isomers.
Key Physical Properties
| Property | Value |
|---|---|
| Molecular formula | C4H10O |
| CAS number | 78-83-1 |
| Boiling point | About 108 °C |
| Flash point, closed cup | About 28 °C |
| Hazard classification | Flammable liquid, category 3; eye irritant |
| Typical exposure limit | TWA about 50 ppm, varies by regulation |
Industrial Applications
Isobutyl acetate production: isobutanol reacts with acetic acid to form isobutyl acetate, a solvent used in lacquers and coatings and as a food flavoring agent.
Plasticizer synthesis: isobutanol is used to produce diisobutyl phthalate (DIBP), a plasticizer for rubber and plastics.
Paints and inks: isobutanol is a solvent that reduces viscosity, improves brush flow, and prevents the deposition of petroleum residues on painted surfaces.
Fuel additive: small amounts of isobutanol are added to gasoline for spark-ignition engines to help prevent carburetor icing.
Extraction and analysis: isobutanol is used for extracting organic compounds and as a mobile phase in thin-layer chromatography.
Storage and Safety Guidelines
Isobutanol should be stored in a cool, well-ventilated, dry environment away from fire and heat sources. It must be kept in tightly sealed metal containers and isolated from oxidizing agents, acids, and strong alkalis. When handling isobutanol, workers should wear chemical goggles, nitrile gloves, and protective clothing because the liquid irritates the eyes and can be absorbed through the skin. In case of fire, alcohol-resistant foam, dry chemical, or carbon dioxide should be used, and water spray may be used to cool exposed containers.
Frequently Asked Questions
What is the chemical structure of 2-methyl-1-propanol?
2-Methyl-1-propanol has the structure (CH3)2CHCH2OH, a branched primary alcohol with the molecular formula C4H10O.
Is isobutanol the same as isobutyl alcohol?
Yes. Isobutanol and isobutyl alcohol are common names for the same compound, 2-methyl-1-propanol.
What is isobutanol used for?
Isobutanol is used to produce isobutyl acetate and DIBP plasticizer, as a solvent in paints and inks, as a gasoline additive, and in chemical extraction and chromatography.
What is the CAS number of isobutanol?
The CAS number of isobutanol is 78-83-1.
Is isobutanol flammable?
Yes. Isobutanol is a category 3 flammable liquid with a closed-cup flash point of about 28 °C.
How should isobutanol be stored?
It should be stored in tightly sealed metal containers in a cool, dry, well-ventilated area, away from oxidizers, acids, strong alkalis, and ignition sources.
