Jump to content

Isopropyl alcohol

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Dakoman (talk | contribs) at 00:05, 10 January 2009 (Reverted 1 edit by 98.192.238.36 identified as vandalism to last revision by Eddietoran. (TW)). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

isopropyl alcohol
isopropyl alcohol
isopropyl alcohol
isopropanol
isopropanol
Names
IUPAC name
propan-2-ol
Other names
2-propanol, isopropanol, isopropyl alcohol
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.000.601 Edit this at Wikidata
RTECS number
  • NT8050000
  • CC(O)C
Properties
C3H8O
Molar mass 60.10 g/mol
Appearance Colorless liquid
Density 0.786 g/cm³, liquid
Melting point −89 °C (−128 °F; 184 K)
Boiling point 82.3 °C (180.1 °F; 355.4 K)
miscible
Acidity (pKa) 16.5 for H on hydroxyl
Viscosity 2.86 cP at 15 °C
1.96 cP at 25 °C[1]
1.77 cP at 30 °C
For 187K-500K, viscosity (cP) =10^(-0.7009+(8.4150E+02/T)+(-8.6068E-03*T)+(8.2964E-06*(T^2))) (Temp in K)[1]
1.66 D (gas)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Flammable
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 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. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
3
0
Flash point 12 °C
Related compounds
Supplementary data page
Isopropyl alcohol (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Isopropyl alcohol (also 2-propanol, iso, isopro, rubbing alcohol, or the abbreviation IPA) is a common name for isopropanol, a colorless, flammable chemical compound with a strong odor. It has the molecular formula C3H8O and is the simplest example of a secondary alcohol, where the alcohol carbon is attached to two other carbons. It is an isomer of propanol.

Production

Isopropyl alcohol is produced by combining water and propene.[2] There are two processes for achieving this: indirect hydration via the sulfuric acid process and direct hydration. The former process, which can use low quality propylene, predominates in the USA while the latter process, which requires high-purity propylene, is more commonly used in Europe. These processes give predominantly isopropyl alcohol rather than 1-propanol because the addition of water or sulfuric acid to propylene follows Markovnikov's rule.

The indirect process reacts propylene with sulfuric acid to form a mixture of sulfate esters. Subsequent hydrolysis of these esters produces isopropyl alcohol. Direct hydration reacts propylene and water, either in gas or liquid phases, at high pressures in the presence of solid or supported acidic catalysts. Both processes require that the isopropyl alcohol be separated from water and other by-products by distillation. Isopropyl alcohol and water form an azeotrope and simple distillation gives a material which is 87.9% by weight isopropyl alcohol and 12.1% by weight water.[3] Pure (anhydrous) isopropyl alcohol is made by azeotropic distillation of the "wet" isopropyl alcohol using either diisopropyl ether or cyclohexane as azeotroping agents.

Availability

Although isopropanol is sometimes sold as "Isopropyl Rubbing Alcohol, 70%" (or 91%) and "Isopropyl Rubbing Alcohol, 99%", there is no isopropyl alcohol in the United States Pharmacopeia formula for rubbing alcohol, U.S.P.

Uses

Isopropyl alcohol is cheaply available. Like acetone, it dissolves a wide range of nonpolar compounds. It is also relatively nontoxic and dries quickly. Thus it is used widely as a solvent and as a cleaning fluid (by dissolving lipophilic contaminants such as oil). Examples of this use include cleaning electronic devices such as contact pins (like those on ROM cartridges), magnetic tape deck and floppy disk drive heads, the lenses of lasers in optical disc drives (e.g. CD, DVD) and removing thermal paste from CPUs. It is also used to clean LCD and glass computer monitor screens (at some risk to the anti-reflection coating of the screen), and used by many music shops to give second-hand or worn records newer-looking sheens. It cleans white boards and other unwanted ink related marks very well (at the risk of damaging the non-stick surface of the white board). Isopropyl alcohol also works well at removing smudges, dirt, and fingerprints from cell phones and PDAs. It is effective at removing residual glue from sticky labels. It can also be used to remove stains from most fabrics, wood, cotton, etc.

As a preservative (for biological specimens) isopropyl alcohol provides a cost-effective (when compared to pure ethanol) and comparatively non-toxic alternative to formaldehyde and other synthetic preservatives. When used for the preservation of specimens in solution concentrations of 90-99% are optimal, though concentrations as low as 70% can be used in emergencies.

Sterilizing pads typically contain a 60-70% solution of isopropanol in water. Isopropyl alcohol is also commonly used as a cleaner and solvent in industry.

Isopropanol is a major ingredient in "dry-gas" fuel additive. In significant quantities, water is a problem in fuel tanks as it separates from the gasoline and can freeze in the supply lines at cold temperatures. The isopropanol does not remove the water from the gasoline; rather, the isopropanol solubilizes the water in the gasoline. Once soluble, the water does not pose the same risk as insoluble water as it will no longer accumulate in the supply lines and freeze. Isopropanol is often sold in aerosol cans as a windscreen de-icer.

Isopropanol is used as a water-drying aide for treating otitis externa, better known as swimmers ear.[4]

Chemistry

Unlike ethanol or methanol, isopropanol can be separated from aqueous solutions by adding a salt such as sodium chloride, sodium sulfate, or any of several other inorganic salts.[5] The process is colloquially called salting out, and causes concentrated isopropanol to separate into a distinct layer.

Being a secondary alcohol, isopropanol can be oxidized to the ketone acetone. This can be achieved using oxidizing agents such as chromic acid, or by dehydrogenation of isopropanol over a heated copper catalyst:

(CH3)2CH-OH → (CH3)2CO + H2

Isopropanol may be converted to 2-bromopropane using phosphorus tribromide, or dehydrated to propylene by heating with sulfuric acid.

Isopropanol is often used as a hydride source in the Meerwein-Ponndorf-Verley reduction.

Like most alcohols, isopropyl alcohol reacts with active metals such as potassium to form alkoxides which can be called isopropoxides. The reaction with aluminium (initiated by a trace of mercury) is used to prepare the catalyst aluminium isopropoxide.

Isopropanol has a maximal absorbance at 204 nm in an ultraviolet-visible spectrum.

Safety

Isopropyl alcohol vapor is heavier than air and is highly flammable with a very wide combustible range. It should be kept away from heat and open flame. When mixed with air or other oxidizers it can explode through deflagration.[6] Isopropyl alcohol has also been reported to form explosive peroxides.[7][6]

Like many organic solvents, long term application to the skin can cause defatting[citation needed].

Toxicology

Isopropyl alcohol is oxidized by the liver into acetone via Alcohol dehydrogenase. Symptoms of isopropyl alcohol poisoning include flushing, headache, dizziness, CNS depression, nausea, vomiting, anesthesia, and coma. Use in well-ventilated areas and use protective gloves while using. Poisoning can occur from ingestion, inhalation, or absorption.

Isopropyl alcohol is about twice as toxic as ethanol, though isopropyl alcohol does not cause an anion gap acidosis as do ethanol and methanol. It produces an elevated osmolal gap, but generally no abnormal anion gap (though this may be seen as a result of hypotension and lactic acidosis). Overdoses may cause a fruity odor on the breath as a result of its metabolism to give acetone which is not further metabolized.[8] Isopropyl alcohol is more potent than ethanol as a CNS depressant, and its metabolite, acetone, is a CNS depressant in its own right. While around 15 g of isopropanol can be fatal to a 70kg human if left untreated, it is not nearly as toxic as methanol or ethylene glycol.[9]

References

  1. ^ a b Yaws, C.L. (1999). Chemical Properties Handbook. McGraw-Hill.
  2. ^ "Isopropyl Alcohol, by John E. Logsdon and Richard A. Loke". Kirk‑Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. Article Online Posting Date: December 4, 2000. {{cite encyclopedia}}: |access-date= requires |url= (help); Check date values in: |date= (help)
  3. ^ CRC Handbook of Chemistry and Physics, 44th ed. pp 2143-2184
  4. ^ http://www.mcw.edu/pediatricoto/CommonHealthProblems/OtitisExternaSwimmersEar.htm
  5. ^ Merck Index of Chemicals and Drugs, 9th ed. monograph 5069
  6. ^ a b "Safety (MSDS) data for 2-propanol". Oxford University. Retrieved 2006-09-28.
  7. ^ Hess, R. K. (1997-06-09). "Chemical Safety Hazard Alert - Isopropanol, Peroxides Result in Explosion & Injury". Brookhaven National Laboratory.
  8. ^ Tiess, D: Z. ges. Hygiene 31, 530-531 (1985)
  9. ^ Calculated from TDLO listed at Oxford University MSDS, assuming weight of 70 kg
Retrieved from "https://en.wikipedia.org/w/index.php?title=Isopropyl_alcohol&oldid=263078561"