What Type of Alcohol Is tert-Butanol?
Alcohols are classified by how many carbon atoms are attached to the carbon that carries the hydroxyl group. In tert-butanol, also called tert-butyl alcohol, 2-methyl-2-propanol or TBA, that alpha carbon is bonded to three methyl groups, giving the structure (CH3)3COH. Because three carbon atoms are attached to the carbon bearing the -OH group, tert-butanol is a tertiary alcohol. This is structurally different from primary alcohols such as ethanol, where the hydroxyl-bearing carbon is bonded to only one other carbon, and from secondary alcohols such as isopropanol, where it is bonded to two. The branched tertiary structure makes the molecule more resistant to oxidation than its straight-chain isomers and gives it a distinctive reactivity profile in esterification, dehydration and substitution reactions.
Key Physical and Chemical Properties
tert-Butanol is a colorless liquid with a mild camphor-like odor. It is unusual among the four isomeric butanols because it mixes with water in all proportions, and it solidifies into crystals at temperatures close to ordinary room temperature.
| Property | Typical value |
| CAS number | 75-65-0 |
| Molecular formula | C4H10O |
| Molecular weight | 74.12 g/mol |
| IUPAC name | 2-methylpropan-2-ol |
| Appearance | Colorless liquid or crystalline solid |
| Melting point | approximately 25 to 26 °C |
| Boiling point | approximately 82 to 83 °C |
| Density | about 0.775 g/mL at 25 °C |
| Flash point | approximately 11 °C, closed cup |
| Solubility | fully miscible with water; also soluble in ethanol, diethyl ether and most organic solvents |
Unlike the other butanol isomers, which dissolve only partially in water, tert-butanol is miscible with water at every ratio. This combination of water miscibility and organic solubility makes it a useful bridge between aqueous and organic phases in formulated systems.
Industrial Applications of tert-Butanol
Solvent and co-solvent use
tert-Butanol is used as a solvent in the manufacture of pharmaceuticals, agrochemicals and specialty chemicals, where its low freezing point and its ability to dissolve both polar and non-polar substances are valuable. It also serves as a reaction medium and as a co-solvent in cleaning and coating formulations.
Denaturant and fuel-related use
Because it is miscible with both water and ethanol, tert-butanol is used as a denaturant for ethanol and as a component of certain fuel and solvent blends. It has been used in oxygenated gasoline formulations and acts as an intermediate for other fuel additives.
Laboratory and analytical use
In analytical and research laboratories, tert-butanol is used as a mobile-phase component, an internal standard and a freeze-drying aid, because it lowers the freezing point of aqueous systems and improves the efficiency of lyophilization.
tert-Butanol as a Synthesis Intermediate
The tertiary alcohol is a convenient source of the tert-butyl group in organic synthesis. It is converted into derivatives such as tert-butyl esters, tert-butyl ethers and tert-butoxide salts, which are widely used as reagents and intermediates in pharmaceutical and fine chemical manufacturing. Dehydration of tert-butanol yields isobutylene, an important monomer and feedstock for butyl rubber and other polymers.
Safety, Storage and Handling
tert-Butanol is a flammable liquid with a relatively low flash point, so it must be kept away from ignition sources and stored in approved containers. It can cause eye and skin irritation, and its vapors may cause drowsiness or respiratory irritation in poorly ventilated areas. Practical precautions include:
Store in tightly closed containers in a cool, well-ventilated area away from heat and open flames
Ground and bond containers when transferring large volumes to prevent static discharge
Wear chemical-resistant gloves, safety goggles and protective clothing
Use local exhaust ventilation or work in a fume hood wherever vapors may be generated
Keep spill containment materials and suitable fire extinguishing equipment nearby
Frequently Asked Questions
Q: What type of alcohol is tert-butanol?
tert-Butanol is a tertiary alcohol: the carbon atom carrying the hydroxyl group is bonded to three methyl groups, giving the structure (CH3)3COH, which distinguishes it from primary and secondary alcohols.
Q: What is the CAS number of tert-butanol?
The CAS registry number of tert-butanol is 75-65-0, its molecular formula is C4H10O, and its IUPAC name is 2-methylpropan-2-ol.
Q: Is tert-butanol miscible with water?
Yes. tert-Butanol is fully miscible with water in all proportions, which is unusual among the butanol isomers and contributes to its value as a co-solvent.
Q: What are the main uses of tert-butanol?
It is used as a solvent in pharmaceutical and agrochemical production, as an ethanol denaturant, as a synthesis intermediate for tert-butyl derivatives and isobutylene, and as a laboratory reagent in lyophilization and chromatography.
Q: What is the melting point of tert-butanol?
tert-Butanol melts at approximately 25 to 26 °C, so it may appear as a crystalline solid in cool environments and as a liquid at normal room temperature.
Q: Is tert-butanol flammable?
Yes. Its flash point is approximately 11 °C in a closed cup, so it must be handled away from ignition sources with adequate ventilation and static precautions.