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ethyl alcohol:see ethanolethanol
or ethyl alcohol,
CH3CH2OH, a colorless liquid with characteristic odor and taste; commonly called grain alcohol or simply alcohol. Properties
Ethanol is a monohydric primary alcohol. It melts at −117.
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(also ethanol), C2H5OH, a colorless, mobile liquid with a characteristic odor and a pungent taste.
Ethyl alcohol has a melting point of – 114.15°C, a boiling point of 78.39°C, and a density of 0.794 g/cm3. It is soluble in water and such organic solvents as ether and acetone. Highly flammable, it has a flash point of 14°C, and mixtures of ethyl alcohol and air are explosive when the concentration of the alcohol is 3.28–18.95 percent by volume. Ethyl alcohol possesses all the chemical properties that are characteristic of monohydric alcohols; for example, it forms alcoholates upon reaction with alkali metals or alkaline-earth metals, and it forms esters upon reaction with acids. Upon oxidation, ethyl alcohol yields acetaldehyde, upon dehydration it gives ethylene and diethyl ether, and upon chlorination it yields chloral.
Ethyl alcohol is one of the most commonly produced organic chemicals. Until the early 1930’s, it was produced exclusively by the fermentation of carbohydrate-containing agricultural products—mainly grains (rye, barley, Indian corn, oats, and millet), potatoes, and beet molasses (seeFERMENTATION and ALCOHOL INDUSTRY). Between the 1930’s and the 1950’s, several methods were developed for synthesizing ethyl alcohol from chemical raw materials; these methods included the hydration of ethylene and the hydrogenation of acetaldehyde. The most important method currently in use is the direct (single-step) hydration of ethylene according to the reaction
CH2=CH2 + H2O → C2H5OH
The reaction is carried out with a phosphoric acid catalyst at a temperature of 280°–300°C and a pressure of 7.2–8.3 meganewtons per sq m (MN/m2), or 72–83 kilograms-force per sq cm (kgf/cm2). In 1976, approximately 800,000 metric tons of ethyl alcohol were produced in the USA; of this total, 550,000 metric tons were manufactured by direct hydration, and the remainder was produced by the fermentation of agricultural products.
In some countries, including the USSR and France, a two-stage hydration of ethylene is used. The process is carried out in the presence of sulfuric acid at a temperature of 75°–80°C and a pressure of 2.48 MN/m2 (24.8 kgf/cm2); in this process, ethylene reacts with the concentrated sulfuric acid to form a mixture of monoethyl and diethyl hydrogen sulfate [C2H5OSO2OH and (C2H5O)2SO2], which is then hydrolyzed at 100°C and 0.3–0.4 MN/m2 (3–1 kgf/cm2) to yield ethyl alcohol and sulfuric acid. In other countries, ethyl alcohol is also produced by the hydrolysis of sulfite waste liquors and the hydrolysis of vegetable matter (seeHYDROLYSIS INDUSTRY).
The purification of technical-grade ethyl alcohol is performed by various methods. For example, ethyl alcohol that is derived from agricultural products is usually purified by rectification in order to remove such impurities as fusel oil. Synthetic ethyl alcohol is separated from such impurities as diethyl ether and acetaldehyde by fractional rectification in the presence of bases or hydrogenation in the vapor phase over nickel catalysts at 105°C and 0.52 MN/m2 (5.2 kgf/cm2). The rectified spirits are an azeotropic mixture, with an ethyl alcohol content of 95.57 percent and a water content of 4.43 percent; the mixture has a boiling point of 78.15°C.
Absolute (anhydrous) ethyl alcohol is required for many purposes. It is industrially produced by removing water in the form of a ternary azeotropic mixture of water, ethanol, and benzene (a special additive). In the laboratory, it is prepared by chemically binding the water to various reagents, including calcium oxide and elemental calcium or magnesium. Ethyl alcohol that is intended for industrial or household use is sometimes denatured (seeDENATURED ALCOHOL).
Ethyl alcohol is used as a solvent in the production of paints, varnishes, pharmaceuticals, perfumes, cosmetics, explosives, motion-picture film, and photographic film. It is used as a raw material in the production of many chemicals, including butadiene and ethyl acetate. The use of ethyl alcohol in the production of protein-vitamin concentrates is also very promising (seeMICROBIOLOGICAL INDUSTRY). Large amounts of ethyl alcohol derived from agricultural products are consumed in the production of alcoholic beverages, such as vodka.
Ethyl alcohol is a narcotic substance that produces characteristic alcoholic stimulation; when taken in large quantities, it depresses the activity of the central nervous system. Ethyl alcohol is also used in medicine—mainly as an external antiseptic and irritant for rubbing and making compresses; it is also used in the production of such pharmaceutical preparations as tinctures and extracts.