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Ethyl alcohol: structure, properties, uses, production

This alcohol has been used as an antiseptic and disinfectant, in addition to its use in the synthesis of medicines and other organic chemicals. Likewise, it has been used as fuel in heaters, lamps, and in combination with gasoline in motor vehicles.

The fermentation of sugar for the production of ethanol is one of the first chemical reactions that primitive man learned. A 9000-year-old pottery has been found in China that contained dry remains of ethanol, indicating that Neolithic man was already consuming alcohol.

But the fermentation of sugars only produced a very low concentration ethanol solution, which is why it was necessary to learn distillation techniques to remove the water and concentrate the alcohol. Thus, Greek alchemists working in Alexandria in the 1st century AD, already knew and used distillation.

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Structure of ethyl alcohol

In the upper image we have the molecular structure of ethanol, CH 3 -CH 2 -OH, represented by a full-space model. It is a fairly polar molecular, since the OH group attracts electronic density towards itself from the carbon skeleton to which it is attached.

As a result, the ethyl alcohol molecules interact through dipole-dipole forces, with the hydrogen bonding type standing out, CH 3 CH 2 OH — OHCH 2 CH 3 . That is why this alcohol has a high boiling point compared to other solvents or organic liquids.

Properties

Physical appearance

Colorless liquid.

Molar mass

46.069 g / mol

Odor

Smell soft and similar to wine.

Flavor

Burning

Density

0.789 g / cm 3 at 20 ºC

Melting point

– 114.14 ºC

Boiling point

78.24 ºC

Water solubility

1 · 10 6 mg / L. That is, it is practically miscible in all proportions.

Miscibility with organic solvents

Ethanol is miscible with acetic acid, acetone, benzene, carbon tetrachloride, chloroform, diethyl ether, ethylene glycol, glycerol, pyridine, and toluene. It is also miscible with light aliphatic hydrocarbons, such as pentane and hexane.

Octanol / water partition coefficient

Log P = – 0.31

Vapor pressure

59.3 mm Hg at 25 ° C. Therefore, it gives off a noticeable amount of fumes.

Vapor density

1.59 in relation to air taken as unity (1)

ignition point

13 ºC

Autoignition temperature

363 ºC

Heat of combustion

1336.8 kJ / mol at 25 ºC

Combustion

Ethanol is a volatile liquid that burns with a blue, smokeless flame, and is virtually invisible to natural light.

0.618 cal / g at 23 ºC

Viscosity

1.2 mPa · s at 20 ºC

Refractive index ηD

1.3611

Ethyl alcohol uses

One of the most common uses of alcohol is as an antiseptic

Medical uses

Antiseptic

Ethanol is used as an antiseptic, as it has a lethal action against bacteria and fungi. It is capable of altering the structure of its plasma membranes, which produces its destruction through the osmotic flows of water that are established.

Also, ethanol can destroy many types of viruses. At the present time, the use of gels containing alcohol is recommended to disinfect the hands and reduce the spread of the coronavirus. Ethanol is also used to disinfect minor superficial wounds.

Drug solvent

Many drugs are poorly soluble in water, using ethanol to increase their solubility. Some cough syrups and mouthwashes have an ethanol content of up to 25%.

Pain treatment

Ethanol is used for therapeutic lysis of nerves or nodes for the relief of chronic intractable pain, present in inoperable cancer or in trigeminal neuralgia.

Treatment of symptomatic thyroid cysts

Percutaneous injections of ethanol are used in the treatment of thyroid cysts, a simple procedure that could avoid the complications of a surgical intervention.

Sedative action

Occasionally, ethanol is administered intravenously for preoperative and postoperative sedation, in those patients for whom other measures are not usable.

Antidote

Ethanol is used systemically to treat poisoning with methanol or ethylene glycol.

Glaucoma

Ethanol is used to lower intraocular pressure in glaucoma patients.

Fuel

The United States, along with Brazil, consumes 90% of the ethanol used as fuel in automobiles. The United States is the largest producer of corn in the world, so it uses corn as a source of ethanol for fuel.

The government subsidized corn growers, increasing fuel ethanol production from 20 million gallons per year to 750 million gallons between 1979 and 1986.

Sugarcane is Brazil’s main source of ethanol for use as fuel. In 1943, due to the Second World War, which made it difficult for oil to enter Brazil, the use of ethanol as fuel increased considerably.

Since 1976, mixtures of ethanol and gasoline have been used as fuel in automobiles, whose ethanol content ranges between 10 and 25%, depending on the production of sugar cane.

Recreational use

Ethanol is present in numerous beverages used in social gatherings and even during family lunch and dinner.

The initial action of alcohol to disinhibit the social behavior of the person produces a pleasant and facilitating environment for interaction between people. However, excess ethanol can trigger toxic and undesirable effects on personal health and on the harmony between meetings or events.

Personal care

Ethanol is present in many cosmetics and beauty products. In addition, due to its astringent action, it is used to clean the skin, removing traces of grease and dirt that soap and water cannot. It is also part of the preparation of many lotions and perfumes.

Food

Vanilla essence, a flavoring used in cakes and pastries, is dissolved in a mixture of ethanol and water. Candies that are filled with certain alcoholic beverages are sold. Alcohol is also used as a flavoring for some sweets.

Obtaining ethyl alcohol

Ethanol is obtained mainly by fermentation of sugars and hydration of ethylene, making tests to produce it from carbon dioxide, lipids and cellulose.

Fermentation

In the fermentation process, the transformation of carbohydrates into ethanol occurs by the action of enzymes present in yeast. Mainly sugar cane, beet, and cereals such as corn and barley are used as raw materials.

The glycolysis enzymes of some yeast species, such as Saccharomyces cerevisiae , are capable of acting on the sugars glucose and sucrose, in order to produce ethanol. The concentration of the ethanol produced is limited by the susceptibility of the yeasts to ethanol.

In any case, the concentration of ethanol produced by fermentation does not exceed 18%. It is therefore necessary to concentrate the ethanol solution using simple distillation. By this method an ethanol solution with a concentration around 95% is obtained.

Finally, fractional distillation and dehydration of 95% alcohol are used for the production of absolute alcohol. The ethanol produced by fermentation is used in medicine, and is reserved as a fuel that complements gasoline.

Ethylene hydration

In this process, ethylene is mixed with deionized water vapor at high temperatures, between 250 and 300 ºC, and under a pressure of 6.8 MPa. The conversion of ethylene to ethanol is catalyzed by phosphoric acid placed on a bed of silica gel or diatomaceous earth.

The ethylene hydration reaction can be outlined as follows:

2 H 4     + H 2 O → CH 3 CH 2 OH

Part of the phosphoric acid is carried away by water vapor and must be neutralized with dilute sodium hydroxide. The concentration of ethanol obtained by hydration of ethylene is low, with a value between 10 and 25%.

Then, the ethanol solution is concentrated by distillation, obtaining a 95% ethanol solution, which can be brought to 100% by fractional distillation and dehydration.

Other methods

Among the alternative methods for the production of ethanol we have the use of carbon dioxide, lipids and cellulose. The use of cellulose is more promising, since materials such as wood, straw, waste papers, etc. can be used as the source of the raw material cellulose. Cellulose is a polymer of glucose and can be used as a source of this carbohydrate.

Toxicity and risks

Homemade alcohol cans are usually found in a concentration of 70% -90%

Inhalation

High concentrations of ethanol vapor can cause drowsiness, eye and upper respiratory tract irritation, manifested by coughing and headache.

Direct contact with skin and eyes

Contact with the skin can cause dryness and, chronically, irritation and dermatitis. Meanwhile, contact with the eyes causes irritation, redness, pain and a burning sensation.

Ingestion

It produces a burning sensation and at the beginning it has a stimulating and pleasant action due to the disinhibition produced. But by continuing to drink alcohol, a nervous breakdown, headache, blurred vision, drowsiness and unconsciousness occur.

Chronic effects

Ethanol affects the central nervous system and the upper respiratory tract. Additionally, liver damage from ingesting ethanol can lead to cirrhosis and later death.

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