Isopropyl alcohol
From Wikipedia, the free encyclopedia
| isopropyl alcohol | |
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| IUPAC name |
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| Other names | 2-propanol, isopropanol, isopropyl alcohol |
| Identifiers | |
| CAS number | [] |
| RTECS number | NT8050000 |
| SMILES |
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| ChemSpider ID | |
| Properties | |
| Molecular formula | C3H7OH |
| Molar mass | 60.10 g/mol |
| Appearance | Colorless liquid |
| Density | (at 20 C) 0.786 g/cm³, liquid |
| Melting point |
−89 °C, 184 K, -128 °F |
| Boiling point |
82.3 °C, 355 K, 180 °F |
| Solubility in water | 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] |
| Dipole moment | 1.66 D (gas) |
| Hazards | |
| MSDS | External MSDS |
| R-phrases | R11 R36 R67 |
| S-phrases | S7 S16 S24 S25 S26 |
| NFPA 704 |
 3
1
0
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| Flash point | 12 °C |
| Related compounds | |
| Related alcohols | 1-Propanol, Ethanol, 2-Butanol |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Isopropyl alcohol (also propan-2-ol, 2-propanol, iso, isopro, isoprop, 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 C3H7OH 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.
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[edit] 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.
[edit] Uses
Isopropyl alcohol is cheaply available. Like acetone, it dissolves a wide range of nonpolar compounds. It is also relatively nontoxic and dries (evaporates) quickly. Thus it is used widely as a solvent and as a cleaning fluid, especially for 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 and disk heads (such as those in audio and video tape recorders and floppy disk drives), the lenses of lasers in optical disc drives (e.g. CD, DVD) and removing thermal paste from IC packages (such as CPUs.) It is also used to clean LCD and glass computer monitor screens (at some risk to the anti-reflection coating of some screens), and used by many music shops to give second-hand or worn records newer-looking sheens (though it may leach plasticizer from vinyl, making it more rigid.)Pure Isopropyl alcohol should not be used to clean vinyl records. A basic reciepe for cleaning vinyl records is: for 1 litre, 50% Isopropyl alcohol, 50% demineralised water, one or two drops of pure detergent such as Kodak photoflow. 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 some sticky labels (but some other adhesives used on tapes and paper labels are resistant to it.) It can also be used to remove stains from most fabrics, wood, cotton, etc. Isopropyl alcohol is also used to remove brake fluid traces from hydraulic disk brake systems, so that the brake fluid (usually DOT 3, DOT 4 or mineral oil) does not contaminate the brake pads, which would result in poor braking. In addition it can also be used to clean paintballs or other oil based products so that they may be reused, commonly knows as "repainting".
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 swimmer's ear.[4]
[edit] 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, since the alcohol is much less soluble in saline solutions than in salt-free water [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 corresponding ketone acetone. This can be achieved using oxidizing agents such as chromic acid, or by dehydrogenation of isopropanol over a heated copper catalyst:
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 maximum absorbance at 204 nm in an ultraviolet-visible spectrum.
[edit] Safety
Isopropyl alcohol vapor is more dense 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.[6][7]
Like many organic solvents, long term application to the skin can cause defatting[citation needed].
[edit] Toxicology
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This article contains too much jargon and may need simplification or further explanation. Please discuss this issue on the talk page, and/or remove or explain jargon terms used in the article. Editing help is available. (October 2008) |
Isopropyl alcohol is oxidized by the liver into acetone by 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, though this may be seen as a result of hypotension and lactic acidosis. Such an acid gap is a chemical abnormality in the body fluids where elevated serum proton concentration (acidity) is balanced by an unusual anion that is not normally analysed, and the lowered pH causes depletion of bicarbonate anion. Isopropyl alcohol does produce an osmolal gap between the calculated and measured osmolalities of serum, as do the other alcohols. 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. Around 15 g of isopropanol can have a toxic effect on a 70 kg human if left untreated. However, it is not nearly as toxic as methanol or ethylene glycol.[9]
[edit] See also
[edit] References
- ^ a b Yaws, C.L. (1999). Chemical Properties Handbook. McGraw-Hill.
- ^ "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.
- ^ CRC Handbook of Chemistry and Physics, 44th ed. pp 2143-2184
- ^ http://www.mcw.edu/pediatricoto/CommonHealthProblems/OtitisExternaSwimmersEar.htm
- ^ Merck Index of Chemicals and Drugs, 9th ed. monograph 5069
- ^ a b "Safety (MSDS) data for 2-propanol". Oxford University. http://physchem.ox.ac.uk/MSDS/PR/2-propanol.html. Retrieved on 2006-09-28.
- ^ Hess, R. K. (1997-06-09). "Chemical Safety Hazard Alert - Isopropanol, Peroxides Result in Explosion & Injury". Brookhaven National Laboratory. http://www.bnl.gov/esh/shsd/programs/Program_Area_Chemicals_Hazard_Alert_Isopropanol.asp.
- ^ Tiess, D: Z. ges. Hygiene 31, 530-531 (1985)
- ^ Calculated from TDLO listed at Oxford University MSDS, assuming weight of 70 kg
[edit] External links
- The US government's Occupational Safety and Health Administration's guidelines for isopropyl alcohol.
- MSDS sheet for Isopropyl Alcohol
- Vapor pressure and liquid density calculation
- Lab Manager Article on Working with Isopropyl Alcohol
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