| Ethanol | |
|---|---|
| [image] | |
| General | |
| Systematic name | Ethanol |
| Other names | Ethyl alcohol, grain alcohol, hydroxyethane |
| Molecular formula | C2H6O |
| SMILES | CCO |
| Molar mass | 46.07 g/mol |
| Appearance | Colorless liquid |
| CAS number | [64-17-5] |
| Properties | |
| Density and phase | 0.789 g/cm3, liquid |
| Solubility in water | Fully Miscible |
| Melting point | −114.3 °C (158.8 K) |
| Boiling point | 78.4 °C (351.6 K) |
| Acidity (pKa) | 15.9 (H+ from OH group) |
| Viscosity | 1.200 cP at 20 °C |
| Dipole moment | 1.69 D (gas) |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Flammable (F) |
| NFPA 704 | [image][image][image] |
| R-phrases | R11 |
| S-phrases | S2, S7, S16 |
| Flash point | 13 °C |
| RTECS number | KQ6300000 |
| Supplementary data page | |
| Structure & properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Related alkanols | Methanol, 1-Propanol 2-Propanol, Butanol |
| Related compounds | Water, Acetone Acetaldehyde, Acetic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references | |
This article is mostly about ethanol as a chemical compound. For beverages containing ethanol, see Alcoholic beverage. For the use of ethanol as a fuel, see Alcohol fuel.
Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808, Nicolas-Théodore de Saussure determined ethanol's chemical formula. In 1858, Archibald Scott Couper published a structural formula for ethanol: this places ethanol among the first chemical compounds to have their chemical structures determined.
For a mixture of ethanol and water, there is a maximum boiling Azeotrope at 96% ethanol and 4% water. For this reason, Fractional distillation of ethanol-water mixtures (of less than 96% ethanol) cannot yield ethanol purer than 96%. Therefore, 95% ethanol in water is a fairly common solvent.
Two competing approaches may be used to produce absolute ethanol. To break the azeotrope for performing distillation, a small amount of Benzene can be added, and the mixture is again fractionally distilled. Benzene forms a tertiary azeotrope with water and ethanol to remove the last of the water, and a binary azeotrope with ethanol removes most of the benzene. The resulting ethanol is water free, for processes that require it. However, several parts per million of benzene remain, so consumption by humans leads to distinctive Liver damage.
Alternatively, a Molecular sieve can be used to selectively absorb the water from the 96% ethanol solution. Synthetic Zeolite in pellet form can be used, as well as corn grits. The zeolite approach is especially of value, for it is possible to recycle the zeolite in a closed system essentially an unlimited number of times, through drying it with a blast of heated CO2. Absolute ethanol produced this way has no residual benzene, and can be used as fuel, or, when diluted, can even be used to fortify port and sherry in traditional winery operations.
Ethanol for use as industrial feedstock and is most often made from Petroleum feedstocks, typically by the acid-catalysed hydration of Ethylene, represented by the Chemical equation
The catalyst is most commonly Phosphoric acid, adsorbed onto a porous support such as Diatomaceous earth or Charcoal. Solid catalysts, mostly various metal oxides, have also been mentioned in the chemical literature.
In an older process, first practised on the industrial scale in the 1930s by Union Carbide, but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated Sulfuric acid to product ethyl sulfate, which was then hydrolyzed to yield ethanol and regenerate the sulfuric acid:
At petroleum prices like those that prevailed through much of the 1990s, ethylene hydration was a decidedly more economical process than fermentation for producing purified ethanol. Recent increases in petroleum prices, coupled with perennial uncertainty in agricultural prices, make forecasting the relative production costs of fermented versus petrochemical ethanol difficult at the present time.
Ethanol for industrial use is normally made unfit for human consumption ("denatured") by the inclusion of small amounts of substances that are either toxic (such as Methanol) or unpleasant (such as Denatonium), thus avoiding the applicable taxes or inventory controls. Denatured ethanol has the UN number UN 1987 and toxic denatured ethanol has UN 1986.
Ethanol is also used as a fuel and the vast majority of ethanol used for this purpose comes from fermentation.
Due to the production process ethanol is rather expensive, averaging about $1.90 (USD) per gallon.
It is easily Soluble in water in all proportions with a slight overall decrease in volume when the two are mixed. Absolute ethanol and 95% ethanol are themselves good solvents, somewhat less polar than water and used in perfumes, paints and tinctures. Other proportions of ethanol with water or other solvents can also be used as a solvent. Alcoholic drinks have a large variety of tastes because various flavor compounds are dissolved during Brewing. When ethanol is produced as a mixing beverage it is a Neutral grain spirit.
A solution of 70% of ethanol is commonly used as a disinfectant. Ethanol is also used in most common antibacterial hand sanitizer gels at a concentration of about 62%. Oddly enough, the peak of the disinfecting power occurs around 70% ethanol; stronger and weaker solutions of ethanol have a lessened ability to disinfect. Ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores.
Wine with less than 16% ethanol cannot protect itself against bacteria. Because of this, port is often fortified with ethanol to at least 18% ethanol by volume to halt fermentation for retaining sweetness and in preparation for aging, at which point it becomes possible to prevent the invasion of bacteria into the port, and to store the port for long periods of time in wooden containers that can 'breathe', thereby permitting the port to age safely without spoiling. Because of ethanol's disinfectant property, alcoholic beverages of 18% ethanol or more by volume can be safely stored for a very long time.
The hydroxyl group on the ethanol Molecule is an extremely weak acid, but upon treatment Alkali metal or a very Strong base, an H+ can be removed to form an ethoxide ion, C2H5O-.