tert-Butyl alcohol

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tert-Butyl alcohol
Skeletal formula of tert-butanolBall and stick model of tert-butanol
Sample of partially crystalised tert-butanol
Identifiers
CAS number75-65-0 YesY
PubChem6386
ChemSpider6146 YesY
UNIIMD83SFE959 YesY
EC number200-889-7
UN number1120
DrugBankDB03900
MeSHtert-Butyl+Alcohol
ChEBICHEBI:45895 YesY
ChEMBLCHEMBL16502 YesY
RTECS numberEO1925000
Beilstein Reference906698
Gmelin Reference1833
Jmol-3D imagesImage 1
Properties
Molecular formulaC4H10O
Molar mass74.12 g mol−1
AppearanceColorless liquid
OdorCamphorous
Density0.775 g/mL
Melting point25 to 26 °C; 77 to 79 °F; 298 to 299 K
Boiling point82 to 83 °C; 179 to 181 °F; 355 to 356 K
Solubility in watermiscible[2]
log P0.584
Vapor pressure4.1 kPa (at 20 °C)
Acidity (pKa)17 [3]
Refractive index (nD)1.387
Thermochemistry
Specific
heat capacity
C
215.37 J K−1 mol−1
Std molar
entropy
So298
189.5 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
−360.04–−358.36 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−2.64479–−2.64321 MJ mol−1
Hazards
MSDSinchem.org
GHS pictogramsThe flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal wordDANGER
GHS hazard statementsH225, H319, H332, H335
GHS precautionary statementsP210, P261, P305+351+338
EU Index603-005-00-1
EU classificationHighly Flammable F Harmful Xn
R-phrasesR11, R20, R36/37
S-phrases(S2), S9, S16, S46
NFPA 704
Flash point11 °C (52 °F; 284 K)
Explosive limits2.4–8.0%
Related compounds
Related butanols2-Butanol

n-Butanol
Isobutanol

Related compounds2-Methyl-2-butanol
Trimethylsilanol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references
 
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tert-Butyl alcohol
Skeletal formula of tert-butanolBall and stick model of tert-butanol
Sample of partially crystalised tert-butanol
Identifiers
CAS number75-65-0 YesY
PubChem6386
ChemSpider6146 YesY
UNIIMD83SFE959 YesY
EC number200-889-7
UN number1120
DrugBankDB03900
MeSHtert-Butyl+Alcohol
ChEBICHEBI:45895 YesY
ChEMBLCHEMBL16502 YesY
RTECS numberEO1925000
Beilstein Reference906698
Gmelin Reference1833
Jmol-3D imagesImage 1
Properties
Molecular formulaC4H10O
Molar mass74.12 g mol−1
AppearanceColorless liquid
OdorCamphorous
Density0.775 g/mL
Melting point25 to 26 °C; 77 to 79 °F; 298 to 299 K
Boiling point82 to 83 °C; 179 to 181 °F; 355 to 356 K
Solubility in watermiscible[2]
log P0.584
Vapor pressure4.1 kPa (at 20 °C)
Acidity (pKa)17 [3]
Refractive index (nD)1.387
Thermochemistry
Specific
heat capacity
C
215.37 J K−1 mol−1
Std molar
entropy
So298
189.5 J K−1 mol−1
Std enthalpy of
formation
ΔfHo298
−360.04–−358.36 kJ mol−1
Std enthalpy of
combustion
ΔcHo298
−2.64479–−2.64321 MJ mol−1
Hazards
MSDSinchem.org
GHS pictogramsThe flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal wordDANGER
GHS hazard statementsH225, H319, H332, H335
GHS precautionary statementsP210, P261, P305+351+338
EU Index603-005-00-1
EU classificationHighly Flammable F Harmful Xn
R-phrasesR11, R20, R36/37
S-phrases(S2), S9, S16, S46
NFPA 704
Flash point11 °C (52 °F; 284 K)
Explosive limits2.4–8.0%
Related compounds
Related butanols2-Butanol

n-Butanol
Isobutanol

Related compounds2-Methyl-2-butanol
Trimethylsilanol
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

tert-Butyl alcohol (TBA), or 2-methyl-2-propanol (2M2P), 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.

Natural occurrence[edit]

t-Butyl alcohol has been identified in beer and chickpeas.[4] It is also found in cassava[5] which is used as fermentation ingredient in certain alcoholic beverages.

Preparation[edit]

tert-Butyl alcohol is derived commercially from isobutane as a co-product 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.

Applications[edit]

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 MTBE and ETBE by reaction with methanol and ethanol, and TBHP by reaction with hydrogen peroxide.

Chemistry[edit]

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

When tert-butyl alcohol 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.[6]

K + tBuOH → tBuOK+ + 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 SN2 reaction.

Conversion to alkyl halide[edit]

tert-Butyl alcohol reacts with hydrogen chloride to form tert-butyl chloride and water via an SN1 mechanism.

The overall reaction, therefore, is:

0-SN1-tBuOH-to-tBuCl-2D-skeletal.png

Because tert-butyl alcohol is a tertiary alcohol, the relative stability of the tert-butyl carbocation in the Step 2 allows the SN1 mechanism to be followed. Primary alcohols generally undergo an SN2 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[edit]

  1. ^ a b c "tert-Butyl Alcohol - Compound Summary". PubChem Compound. National Center for Biotechnology Information. 2005-03-26. Retrieved 2012-05-19. 
  2. ^ http://www.inchem.org/documents/icsc/icsc/eics0114.htm
  3. ^ Reeve, W.; Erikson, C.M.; Aluotto, P.F. Can. J. Chem, 1979, 57, 2747.
  4. ^ http://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+50
  5. ^ http://www.sc.mahidol.ac.th/scbc/bc_internet/publication/696.pdf
  6. ^ Johnson, W. S.; Schneider, W. P. (1950), "β-Carbethoxy-γ,γ-diphenylvinylacetic acid", Org. Synth. 30: 18 ; Coll. Vol. 4: 132 

External links[edit]