2-Butanol

2-Butanol, or sec-butanol, is an organic compound with formula CH3CH(OH)CH2CH3. This secondary alcohol is a flammable, colorless liquid that is soluble in 3 parts water and completely miscible with organic solvents. It is produced on a large scale, primarily as a precursor to the industrial solvent methyl ethyl ketone. 2-Butanol is chiral and thus can be obtained as either of two stereoisomers designated as (R)-(−)-2-butanol and (S)-(+)-2-butanol. It is normally encountered as a 1:1 mixture of the two stereoisomers — a racemic mixture.

(R)-(−)-2-butanol
(S)-(+)-2-butanol
2-Butanol
Names
IUPAC name
Butan-2-ol[1]
Other names
sec-Butanol[2]
sec-Butyl alcohol
2-Butanol
2-Butyl alcohol
Identifiers
CAS Number
3D model (JSmol)
Beilstein Reference
 773649

1718764 (R)
1718763 (S)

ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.001.053
EC Number
  • 201-158-5
Gmelin Reference
 1686

396584 (R)
25655 (S)

MeSH 2-butanol
PubChem CID
RTECS number
  • EO1750000
UN number 1120
Properties
Chemical formula
 C4H10O
Molar mass 74.123 g·mol−1
Density 0.808 g cm−3
Melting point −115 °C; −175 °F; 158 K
Boiling point 98 to 100 °C; 208 to 212 °F; 371 to 373 K
Solubility in water
 290 g/L[3]
log P 0.683
Vapor pressure 1.67 kPa (at 20 °C)
Acidity (pKa) 17.6 [4]
Magnetic susceptibility (χ)
 −5.7683×10−5 cm3 mol−1
Refractive index (nD)
 1.3978 (at 20 °C)
Thermochemistry
Heat capacity (C)
 197.1 J K−1 mol−1
Std molar
entropy (So298)
 213.1 J K−1 mol−1
Std enthalpy of
formation (ΔfH⦵298)
 −343.3 to −342.1 kJ mol−1
Std enthalpy of
combustion (ΔcH⦵298)
 −2.6611 to −2.6601 MJ mol−1
Hazards
Safety data sheet inchem.org
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H226, H319, H335, H336
GHS precautionary statements
 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 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
1
0
Flash point 22 to 27 °C (72 to 81 °F; 295 to 300 K)
Autoignition
temperature
 405 °C (761 °F; 678 K)
Explosive limits 1.7–9.8%
Lethal dose or concentration (LD, LC):
16,000 ppm (rat, 4 hr)
10,670 ppm (mouse, 3.75 hr)
16,000 ppm (mouse, 2.67 hr)[5]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 150 ppm (450 mg/m3)[5]
REL (Recommended)
 TWA 100 ppm (305 mg/m3) ST 150 ppm (455 mg/m3)[5]
IDLH (Immediate danger)
 2000 ppm[5]
Related compounds
Related butanols
 n-Butanol
Isobutanol
tert-Butanol
Related compounds
 Butanone
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

Manufacture and applications

2-Butanol is manufactured industrially by the hydration of 1-butene or 2-butene:

Sulfuric acid is used as a catalyst for this conversion.[6]

In the laboratory it can be prepared via Grignard reaction by reacting ethylmagnesium bromide with acetaldehyde in dried diethyl ether or tetrahydrofuran.

Although some 2-butanol is used as a solvent, it is mainly converted to butanone (methyl ethyl ketone, MEK), which is an important industrial solvent and found in many domestic cleaning agents and paint removers. Volatile esters of 2-butanol have pleasant aromas and are used in small amounts as perfumes or in artificial flavors.[6]

Solubility

The solubility of 2-butanol is incorrect in most sources,[3] including some of the most well-known references such as the Merck Index, the CRC Handbook of Chemistry and Physics, and Lange's Handbook of Chemistry. Even the International Programme on Chemical Safety lists the wrong solubility. This widespread error originated because of Beilstein's Handbuch der Organischen Chemie (Handbook of Organic Chemistry). This work cites a false solubility of 12.5 g/100 g water. Many other sources used this solubility, which has snowballed into a widespread error in the industrial world. The correct data (35.0 g/100 g at 20 °C, 29 g/100 g at 25 °C, and 22 g/100 g at 30 °C) were first published in 1886 by Alexejew and then similar data was reported by other scientists including Dolgolenko and Dryer in 1907 and 1913, respectively.

Safety

Like other butanols, 2-butanol has low acute toxicity. The LD50 is 4400 mg/kg (rat, oral).[6]

Several explosions have been reported[7] during the conventional distillation of 2-butanol, apparently due to the buildup of peroxides with the boiling point higher than that of pure alcohol (and therefore concentrating in the still pot during distillation). As alcohols, unlike ethers, are not widely known to be capable of forming peroxide impurities, the danger is likely to be overlooked.

References
  1. "2-butanol - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. Retrieved 12 October 2011.
  2. "Alcohols Rule C-201.1". Nomenclature of Organic Chemistry (The IUPAC 'Blue Book'), Sections A, B, C, D, E, F, and H. Oxford: Pergamon Press. 1979. Designations such as isopropanol, sec-butanol, and tert-butanol are incorrect because there are no hydrocarbons isopropane, sec-butane, and tert-butane to which the suffix "-ol" can be added; such names should be abandoned. Isopropyl alcohol, sec-butyl alcohol, and tert-butyl alcohol are, however, permissible (see Rule C-201.3) because the radicals isopropyl, sec-butyl, and tert-butyl do exist.
  3. Alger, Donald B. (November 1991). "The water solubility of 2-butanol: A widespread error". Journal of Chemical Education. 68 (11): 939. doi:10.1021/ed068p939.1.
  4. Serjeant, E.P., Dempsey B.; Ionisation Constants of Organic Acids in Aqueous Solution. International Union of Pure and Applied Chemistry (IUPAC). IUPAC Chemical Data Series No. 23, 1979. New York, New York: Pergamon Press, Inc., p. 989
  5. NIOSH Pocket Guide to Chemical Hazards. "#0077". National Institute for Occupational Safety and Health (NIOSH).
  6. Hahn, Heinz-Dieter; Dämbkes, Georg; Rupprich, Norbert (2005). "Butanols". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH..
  7. Doyle, R. R. (1986). "2-Butanol safety warning". Journal of Chemical Education. 63 (2): 186. doi:10.1021/ed063p186.2., and references cited therein.
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