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tert-Butanol

Names
IUPAC name 2-Methylpropan-2-ol
Other names tert-Butyl alcohol Dimethylethanol 1,1-Dimethylethanol 2-Methyl-2-propanol
Identifiers
CAS Number	75-65-0
3D model (JSmol)	Interactive image
Beilstein Reference	906698
ChEBI	CHEBI:45895
ChEMBL	ChEMBL16502
ChemSpider	6146
DrugBank	DB03900
ECHA InfoCard	100.000.809
EC Number	200-889-7
Gmelin Reference	1833
MeSH	tert-Butyl+Alcohol
PubChem CID	6386
RTECS number	EO1925000
UNII	MD83SFE959
UN number	1120
CompTox Dashboard (EPA)	DTXSID8020204
InChI InChI=1S/C4H10O/c1-4(2,3)5/h5H,1-3H3Key: DKGAVHZHDRPRBM-UHFFFAOYSA-N
SMILES CC(C)(C)O
Properties
Chemical formula	C4H10O
Molar mass	74.123 g·mol
Appearance	Colorless liquid
Odor	Camphorous
Density	780.9 mg cm
log P	0.584
Vapor pressure	4.1 kPa (at 20 °C)
Refractive index (nD)	1.387
Thermochemistry
Heat capacity (C)	215.37 J K mol
Std molar entropy (S298)	189.5 J K mol
Std enthalpy of formation (ΔfH298)	−360.04–−358.36 kJ mol
Std enthalpy of combustion (ΔcH298)	−2.64479–−2.64321 MJ mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H319, H332, H335
Precautionary statements	P210, P261, P305+P351+P338
NFPA 704 (fire diamond)	1 3 0
Flash point	11 °C
Explosive limits	2.4–8.0%
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). N verify (what is  ?) Infobox references

tert-Butanol, or 2-methyl-2-propanol, is the simplest tertiary alcohol. It is one of the four isomers of butanol. tert-Butanol is a clear liquid (or a colorless solid, depending on the ambient temperature) 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 production. 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 → tBuOK + /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 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 stabilized through hyperconjugation where the neighboring C–H sigma bonds donate electrons into the empty p-orbital of the carbocation.

References

1. "tert-Butyl Alcohol - Compound Summary". PubChem Compound. USA: National Cnter for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 2 November 2011.
2. Johnson, William S.; Schneider, William P. (1950). "β-Carbethoxy-γ,γ-diphenylvinylacetic acid". Organic Syntheses. 30: 18; Collected Volumes, vol. 4, p. 132.

External links

• International Chemical Safety Card 0114
• NIOSH Pocket Guide to Chemical Hazards. "#0078". National Institute for Occupational Safety and Health (NIOSH).
• IPCS Environmental Health Criteria 65: Butanols: four isomers
• IPCS Health and Safety Guide 7: tert-Butanol

• Alcohols
• Alcohol solvents
• Oxygenates