tert-Butyl alcohol

tert-Butyl alcohol (TBA), also called tert-butanol or t-butanol, is the simplest tertiary alcohol, with a formula of (CH3)3COH (sometimes represented as t-BuOH). It is one of the four isomers of butanol.[lower-alpha 1] tert-Butyl alcohol is a colorless solid, which melts near room temperature and has a camphor-like odor. It is miscible with water, ethanol and diethyl ether.

tert-Butyl alcohol
Skeletal formula of tert-butyl alcohol
Ball and stick model of tert-butyl alcohol
Names
Preferred IUPAC name
2-Methylpropan-2-ol
Other names
  • t-Butyl alcohol
  • tert-Butanol
  • t-Butanol
  • t-BuOH
  • Trimethyl carbinol[1]
  • 2-Methyl-2-propanol
  • 2M2P
Identifiers
3D model (JSmol)
906698
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.809
EC Number
  • 200-889-7
1833
MeSH tert-Butyl+Alcohol
RTECS number
  • EO1925000
UNII
UN number 1120
Properties
C4H10O
Molar mass 74.123 g·mol−1
Appearance Colorless solid
Odor Camphorous
Density 0.775 g/mL
Melting point 25 to 26 °C; 77 to 79 °F; 298 to 299 K
Boiling point 82 to 83 °C; 179 to 181 °F; 355 to 356 K
miscible[2]
log P 0.584
Vapor pressure 4.1 kPa (at 20 °C)
Acidity (pKa) 16.54 [3]
5.742×10−5 cm3/mol
1.387
1.31 D
Thermochemistry
215.37 J K−1 mol−1
189.5 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −360.04 to −358.36 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 −2.64479 to −2.64321 MJ mol−1
Hazards
Safety data sheet inchem.org
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H225, H319, H332, H335
P210, P261, P305+351+338
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 11 °C (52 °F; 284 K)
480 °C (896 °F; 753 K)
Explosive limits 2.4–8.0%
Lethal dose or concentration (LD, LC):
3559 mg/kg (rabbit, oral)
3500 mg/kg (rat, oral)[4]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 100 ppm (300 mg/m3)[1]
REL (Recommended)
 TWA 100 ppm (300 mg/m3) ST 150 ppm (450 mg/m3)[1]
IDLH (Immediate danger)
 1600 ppm[1]
Related compounds
Related butanols
 2-Butanol

n-Butanol
Isobutanol

Related compounds
 2-Methyl-2-butanol
Trimethylsilanol

Nonafluoro-tert-butyl alcohol

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Natural occurrence

tert-Butyl alcohol has been identified in beer and chickpeas.[5] It is also found in cassava,[6] which is used as a fermentation ingredient in certain alcoholic beverages.

Preparation

tert-Butyl alcohol is derived commercially from isobutane as a coproduct of propylene oxide production. It can also be produced by the catalytic hydration of isobutylene, or by a Grignard reaction between acetone and methylmagnesium chloride.

Purification cannot be performed by simple distillation due to formation of an azeotrope with water, although initial drying of the solvent containing large amounts of water is performed by adding benzene to form a tertiary azeotrope and distilling off the water. Smaller amounts of water are removed by drying with calcium oxide (CaO), potassium carbonate (K2CO3), calcium sulfate (CaSO4), or magnesium sulfate (MgSO4), followed by fractional distillation. Anhydrous tert-butyl alcohol is obtained by further refluxing and distilling from magnesium activated with iodine, or alkali metals such as sodium or potassium. Other methods include the use of 4 Å molecular sieves, aluminium tert-butylate, calcium hydride (CaH2), or fractional crystallization under inert atmosphere.[7]

Applications

tert-Butyl alcohol is used as a solvent, ethanol denaturant, paint remover ingredient, and gasoline octane booster and oxygenate. It is a chemical intermediate used to produce methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) by reaction with methanol and ethanol, respectively, and tert-butyl hydroperoxide (TBHP) by reaction with hydrogen peroxide.

Reactions

As a tertiary alcohol, tert-butyl alcohol is more resistant to oxidation than the other isomers of butanol.

tert-Butyl alcohol is deprotonated with a strong base to give the alkoxide. Particular common is potassium tert-butoxide, which is prepared by treating tert-butanol with potassium metal.[8]

K + t-BuOH → t-BuO−K+ + 1/2 H2

The tert-butoxide is a strong, non-nucleophilic base in organic chemistry. It readily abstracts acidic protons from substrates, but its steric bulk inhibits the group from participating in nucleophilic substitution, such as in a Williamson ether synthesis or an SN2 reaction.

tert-Butyl alcohol reacts with hydrogen chloride to form tert-butyl chloride.

O-Chlorination of tert-butyl alcohol with hypochlorous acid to give tert-butyl hypochlorite:[9]

(CH3)3COH + HOCl → (CH3)3COCl + H2O

Pharmacology and Toxicology

There is limited data on the pharmacology and toxicology of tert-butanol in humans and other animals.[10] Human exposure may occur due to fuel oxygenate metabolism. Tert-butanol is poorly absorbed through skin but rapidly absorbed if inhaled or ingested. Tert-butanol is irritating to skin or eyes. Toxicity of single doses is usually low but high doses can produce a sedative or anesthetic effect.

Notes
  1. The other isomers of tert-Butyl alcohol, (CH3)3COH, are Isobutanol, (CH3)2CHCH2OH, 2-Butanol, CH3CH2CH(OH)CH3, and n-Butanol, CH3CH2CH2CH2OH. All of these compounds have the same overall chemical formula, C4H10O, and as such they are considered isomers.
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References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0078". National Institute for Occupational Safety and Health (NIOSH).
  2. "ICSC 0114 – tert-Butanol". Inchem.org. Retrieved 29 March 2018.
  3. Reeve, W.; Erikson, C. M.; Aluotto, P. F. (1979). "tert-Butyl alcohol". Can. J. Chem. 57: 2747. doi:10.1139/v79-444.
  4. "tert-Butyl alcohol". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. "t-Butyl Alcohol". National Library of Medicine HSDB Database. National Institute for Health. Retrieved 29 March 2018.
  6. "Archived copy" (PDF). Archived from the original (PDF) on 2016-03-04. Retrieved 2013-03-05.CS1 maint: archived copy as title (link)
  7. Perrin, D. D.; Armarego, W. L. F. (1988). Purification of Laboratory Chemicals (3rd ed.). Pergamon Press.
  8. Johnson, W. S.; Schneider, W. P. (1950). "β-Carbethoxy-γ,γ-diphenylvinylacetic acid". Organic Syntheses. 30: 18. doi:10.15227/orgsyn.030.0018.
  9. Mintz, H. M.; Walling, C. (1969). "t-Butyl Hypochlorite". Org. Synth. 49: 9. doi:10.15227/orgsyn.049.0009.
  10. Douglas McGregor (2010). "Tertiary-Butanol: a toxicological review". Critical Reviews in Toxicology. 40 (8): 697–727. doi:10.3109/10408444.2010.494249. PMID 20722584.
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