Tert-Butanol

tert-Butanol
IUPAC name	2-Methyl-2-propanol
Other names	t-Butanol tert-Butanol t-Butyl alcohol tert-Butyl alcohol tertiary-Butyl alcohol 1,1 - dimethylethanol dimethylethanol
Identifiers
CAS number	[75-65-0]
SMILES	C(C)(C)(C)O
Properties
Chemical formula	C4H9OH
Molar mass	74.1216(42) g/mol
Appearance	colorless liquid, semi-solid or solid
Density	0.78086 g/cm³
Melting point	25.69 °C, 299 K, 78 °F
Boiling point	82.4 °C, 356 K, 180 °F
Hazards
Material safety data sheet (MSDS)	Oxford MSDS
NFPA 704
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

tert-Butanol, or 2-methyl-2-propanol (colourless liquid or white solid, depending on the ambient temperature), is the simplest tertiary alcohol. It is one of the four isomers of butanol. tert-Butanol is a clear liquid with a camphor-like odor. It is very soluble in water and miscible with ethanol and diethyl ether. It is unique among the isomers of butanol because it tends to be a solid at room temperature, with a melting point slightly above 25 °C.

Preparation

tert-Butanol is derived commercially from isobutane as a co-product of propylene oxide producion. It can also be produced by the catalytic hydration of isobutylene.

Applications

tert-Butanol is used as a solvent, as a denaturant for ethanol, as an ingredient in paint removers, as an octane booster for gasoline, as an oxygenate gasoline additive, and as an intermediate in the synthesis of other chemical commodities such as MTBE, ETBE, TBHP, other flavors and perfumes.

Chemistry

As a tertiary alcohol, tert-butanol is more stable to oxidation and less reactive than the other isomers of butanol.

When tert-butanol is deprotonated with a strong base, the product is an alkoxide anion. In this case, it is tert-butoxide. For example, the commonly used organic reagent potassium tert-butoxide is prepared by refluxing dry tert-butanol with potassium metal.

K + tBuOH → tBuO⁻K⁺ + ¹/₂ H₂

The tert-butoxide species is itself useful as a strong, non-nucleophilic base in organic chemistry. It is able to abstract acidic protons from the substrate molecule readily, but its steric bulk inhibits the group from participating in nucleophilic substitution, such as in a Williamson ether synthesis or an S_N2 reaction.

Conversion to alkyl halide

tert-Butanol (also tert-butyl alcohol) reacts with hydrogen chloride to form tert-butyl chloride and water via an S_N1 mechanism.

Step 1	Step 2	Step 3

The overall reaction, therefore, is:

Because tert-butanol is a tertiary alcohol, the relative stability of the tert-butyl carbocation in the Step 2 allows the S_N1 mechanism to be followed. Primary alcohols generally undergo an S_N2 mechanism because the relative stability of a primary carbocation intermediate is very low. The tertiary carbocation in this case is able to stabilize itself better due to electron donation from surrounding sp³ hybridized carbons.