1-Butanol, commonly known as n-butanol or n-butyl alcohol, is a colorless, transparent liquid with a characteristic odor. With the CAS number 71-36-3 and the molecular formula C4H10O, it is one of the four isomeric butanols and the straight-chain primary alcohol among them. Thanks to its stable structure and balanced solvency profile, 1-butanol is widely regarded as an excellent solvent and a versatile chemical intermediate.
What Is 1-Butanol (N-Butanol)?
1-Butanol is produced industrially mainly by the oxo process, in which propylene undergoes hydroformylation followed by hydrogenation, or by the older fermentation route using carbohydrates. It is a primary alcohol with the hydroxyl group attached to the terminal carbon of a four-carbon chain, which gives it a higher boiling point and lower volatility than ethanol or isopropanol.
Key properties of 1-butanol include a molecular weight of 74.12 g/mol, a boiling point of approximately 117.7 °C, a melting point of about -89.8 °C, a density of about 0.81 g/cm3 at 20 °C and a flash point of approximately 35 °C. It is moderately soluble in water, with a solubility of about 7.7 g per 100 mL at 20 °C, and it is fully miscible with most organic solvents, including ethanol, ether, acetone and aromatic hydrocarbons.
Key Physical and Chemical Properties
The solvent power of 1-butanol comes from its dual character: the hydroxyl group provides hydrogen-bonding ability toward polar solutes, while the butyl chain contributes affinity for non-polar substances. This makes it a useful coupling solvent that can bridge aqueous and organic phases in a single formulation.
Its evaporation rate is slower than that of ethanol and isopropanol but faster than that of glycol ethers and esters such as butyl acetate. This intermediate volatility is valuable in coatings, where it prevents too-rapid drying, improves levelling and reduces surface defects such as blushing and orange peel. The relatively high flash point compared with ethanol also improves handling safety in industrial operations.
Why 1-Butanol Excels as a Solvent in Coatings and Inks
In the coatings industry, n-butanol is used as a solvent and co-solvent in alkyd, acrylic, epoxy, polyurethane and nitrocellulose systems. It dissolves many film-forming resins, improves flow and levelling, and helps control the evaporation profile of the solvent blend. In waterborne formulations, it acts as a coalescing aid that promotes film formation and enhances gloss and adhesion.
In printing inks, 1-butanol improves pigment wetting and dispersion, reduces viscosity and speeds up drying without causing excessive skinning. In adhesives and sealants, it is used to adjust open time and tack. It is also an effective cleaner and degreaser for metal parts, printing rollers and electronic components, where it removes grease, flux residues and oils without attacking most substrates.
Chemical Intermediates: Esters, Ethers and Oxidation Products
Through esterification with carboxylic acids, n-butanol produces a family of commercially important esters. Butyl acrylate is a key monomer for acrylic resins and pressure-sensitive adhesives; butyl acetate is a widely used solvent in coatings, inks and nail care; and butyl butyrate contributes fruity notes to fragrances and food flavorings. These esters benefit from the hydrophobic butyl chain, which lowers water sensitivity in the final polymer or formulation.
Through etherification, 1-butanol yields butyl glycol ether and diethylene glycol butyl ether, which are slow-evaporating solvents used in coatings, inks and industrial cleaners. Oxidation of n-butanol produces butyraldehyde and butyric acid, which are intermediates for plasticizers, pharmaceuticals and food preservatives. These derivative pathways make 1-butanol a cornerstone of the C4 chemical value chain.
Pharmaceutical, Laboratory and Cleaning Applications
In pharmaceutical manufacturing, 1-butanol is used as a solvent and crystallization aid in the production of antibiotics such as cephalosporins, and as a reaction medium for ester and ether syntheses. In laboratories, it serves as a mobile phase component in chromatography, an extraction solvent for natural products and a reagent in esterification and dehydration reactions.
In cleaning applications, n-butanol is found in industrial degreasers, paint strippers and graffiti removers. Its ability to dissolve oils, waxes, resins and cured coatings makes it effective for equipment maintenance, and its compatibility with water allows it to be rinsed away after use. Because of its moderate toxicity, however, it should always be used with adequate ventilation and personal protective equipment.
Safety, Handling and Storage Considerations
1-Butanol is a flammable liquid with a flash point of about 35 °C, so it must be stored away from ignition sources, sparks and open flames. Its vapor can form explosive mixtures with air, and the vapor is heavier than air, tending to accumulate in low-lying areas. Adequate ventilation and grounded containers are essential in storage and transfer areas.
Exposure to high vapor concentrations can irritate the eyes, respiratory tract and skin. The occupational exposure limit is commonly set at 50 ppm as an 8-hour time-weighted average in many jurisdictions. Use gloves, safety goggles and respiratory protection where vapor levels may exceed the limit, and wash skin promptly after contact. Waste n-butanol should be collected and disposed of as chemical waste in accordance with local environmental regulations, never poured into drains.
Frequently Asked Questions
Is 1-butanol the same as n-butanol?
Yes. 1-Butanol and n-butanol are two names for the same straight-chain primary alcohol, CH3CH2CH2CH2OH, with the CAS number 71-36-3.
What is the difference between 1-butanol and 2-butanol?
1-Butanol is a primary alcohol with the hydroxyl group at the end of the chain, while 2-butanol is a secondary alcohol with the hydroxyl group on the second carbon. The isomers differ in boiling point, reactivity and hydrogen-bonding behavior, and they are produced by different routes.
Is n-butanol miscible with water?
1-Butanol is only partially miscible with water, dissolving to about 7.7 g per 100 mL at 20 °C. It is fully miscible with most organic solvents, and the two-phase behavior with water is sometimes used in extraction processes.
What esters are made from 1-butanol?
The most important esters are butyl acetate, butyl acrylate and butyl butyrate. Butyl acetate is a major industrial solvent, butyl acrylate is a monomer for acrylic polymers, and butyl butyrate is used in flavors and fragrances.
Is butanol flammable?
Yes. 1-Butanol has a flash point of approximately 35 °C and is classified as a flammable liquid. It should be stored away from heat, sparks and open flames, and handled with ventilation.
What is the boiling point of 1-butanol?
The normal boiling point of 1-butanol is approximately 117.7 °C, which is higher than ethanol and isopropanol and contributes to its slower evaporation in coating applications.