Definition and meaning of tert-Butanol

tert-Butanol
IUPAC name 2-Methylpropan-2-ol[1]
Other names tert-Butyl alcohol[1] Dimethylethanol[citation needed] 1,1-Dimethylethanol[citation needed] 2-Methyl-2-propanol[1]
Identifiers
CAS number	75-65-0 Y
PubChem	6386
ChemSpider	6146 Y
UNII	MD83SFE959 Y
EC number	200-889-7
UN number	1120
DrugBank	DB03900
MeSH	tert-Butyl+Alcohol
ChEBI	CHEBI:45895 Y
ChEMBL	CHEMBL16502 Y
RTECS number	EO1925000
Beilstein Reference	906698
Gmelin Reference	1833
Jmol-3D images	Image 1
SMILES CC(C)(C)O
InChI InChI=1S/C4H10O/c1-4(2,3)5/h5H,1-3H3 Y Key: DKGAVHZHDRPRBM-UHFFFAOYSA-N Y
Properties
Molecular formula	C4H10O
Molar mass	74.12 g mol−1
Appearance	Colorless liquid
Odor	Camphorous
Density	0.775 g/mL
Melting point	25-26 °C, 298-299 K, 77-79 °F
Boiling point	82-83 °C, 355-356 K, 179-181 °F
log P	0.584
Vapor pressure	4.1 kPa (at 20 °C)
Refractive index (nD)	1.387
Thermochemistry
Std enthalpy of formation ΔfHo298	−360.04–−358.36 kJ mol−1
Std enthalpy of combustion ΔcHo298	−2.64479–−2.64321 MJ mol−1
Standard molar entropy So298	189.5 J K−1 mol−1
Specific heat capacity, C	215.37 J K−1 mol−1
Hazards
MSDS	inchem.org
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H225, H319, H332, H335
GHS precautionary statements	P210, P261, P305+351+338
EU Index	603-005-00-1
EU classification	F Xn
R-phrases	R11, R20, R36/37
S-phrases	(S2), S9, S16, S46
NFPA 704	3 1 0
Flash point	11 °C
Autoignition temperature	480 °C
Explosive limits	2.4–8.0%
Related compounds
Related butanols	2-Butanol n-Butanol Isobutanol
Related compounds	2-Methyl-2-butanol
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.^[2]

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 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

  External links

• International Chemical Safety Card 0114
• NIOSH Pocket Guide to Chemical Hazards 0078
• IPCS Environmental Health Criteria 65: Butanols: four isomers
• IPCS Health and Safety Guide 7: tert-Butanol