Ethanol: Structure, Preparation, Properties, Tests, Uses

Ethanol

Ethanol, commonly known as ethyl alcohol, is an organic compound having the chemical formula C2H5OH.

Ethyl alcohol is the most widely used solvent and raw ingredient.  It is used in laboratories and the chemical industry. Much of this alcohol originates from ethylene. Ethyl alcohol is used in medicine as a disinfectant and antiseptic. It can be used as a chemical solvent, in organic compound production, and as an alternative fuel source.

Ethyl alcohol is an important industrial chemical, used as a solvent for the production of other organic compounds. It is also used as a petrol additive (creating a gasohol combination). Many alcoholic beverages, including beer, wine, and distilled spirits, consist of ethanol as an intoxicating component.

Structure of ethanol

The chemical formula for ethanol is C2H6O. The chemical formula of ethanol can be represented as CH3 – CH2– OH, C2H5OH, which is an ethyl group coupled to a hydroxyl group.

EtOH is a common abbreviation for the formula. Ethanol is a highly volatile, flammable, colorless liquid with a distinct odor. Ethanol is a psychoactive chemical, a recreational drug, and a component of alcoholic beverages.

Preparation of ethanol

From fermentation

Fermentation is the process of converting carbohydrates to ethanol by developing yeast cells. In industries, yeasts (Saccharomyces cerevisiae, S. uvarum, S. carlsbergensis, Candida brassicae, C. utilis, Kluyveromyces fragilis, K. lactis) and bacteria (Zymomonas mobilis) have both been used to produce ethyl alcohol. Saccharomyces cerevisiae is used in the commercial production of ethanol. Sugar crops such as beets and sugarcane, as well as grain crops such as corn (maize), are the primary raw materials fermented for the manufacturing of industrial alcohol.

Ethyl alcohol is a renewable source of energy and a dependable alternative to fossil fuels, and its demand for diverse uses grows over time. Molasses is used to make ethyl alcohol in industries. Molasses are byproducts of the sugar cane processing process. Yeast cells are added during the fermentation process. Zymase, a yeast enzyme, converts simple carbohydrates to ethanol and carbon dioxide. The yeast’s enzymatic process in fermentation produces primarily ethyl alcohol, CO2, and heat.

 During fermentation, molasses is first diluted with water in a 1:5 (molasses: water) volume ratio. If the nitrogen concentration of molasses is low, it is supplemented with ammonium sulfate to ensure that yeast receives an appropriate quantity of nitrogen. The resultant solution is transferred to a big tank, where yeast is added and temperature is maintained at 35°C for 2 to 3 days. During this time, the yeast enzymes sucrose and zymase transform sugar into ethyl alcohol.

During fermentation, the enzyme invertase first converts sucrose to glucose and fructose, and subsequently, zymase converts glucose to ethyl alcohol.

C12H22O11 + H2O → C6H12O6 + C6H12O6

C6H12O6 → C2H5OH + CO2

Ethanol’s boiling point (78.4°C) is somewhat lower than water’s boiling temperature (100°C). Distillation cannot entirely separate these components since the difference in boiling points is so small. Instead, an azeotropic mixture (made up of 96% ethanol and 4% water) is formed. Alcohol azeotropic mixtures cannot be further concentrated through distillation. However, the rectified spirit is created through the process of distillation. Dehydration of rectified spirit yields ethyl alcohol or absolute alcohol.

From hydration of ethene

During the hydration, a water molecule combines with an alkene to produce an alcohol process. Ethyl alcohol can be preparaed by reacting an alkene with a water molecule i.e., called hydration of ethene. When ethylene molecules combine with sulfuric acid in the presence of water, an alcohol, ethyl alcohol, is formed. This reaction involves three steps

  1. An electrophilic attack on the hydronium ion occurs, which pronates the ethene to produce a carbocation.
  2. The water molecule attacks the carbocation in the second stage.
  3. Finally, deprotonation produces ethyl alcohol.

Properties of ethanol

  • Ethyl alcohol is a colorless liquid.
  • At room temperature, it is liquid.
  • It has a slightly sweet odor.
  • The molecular Weight of ethanol is  46.07 (g/mol).
  • It has a melting point of 156K and a boiling point of 351K. 
  • It is readily soluble in water and a variety of organic solvents.
  • It is very flammable and easily burns in the presence of an ignition source.
  • Ethyl alcohol is a combustible liquid. When burned in the presence of oxygen, it emits carbon dioxide, water, heat, and light.

Ethanol: Solvent properties

Its ability to mix with water makes ethyl alcohol a versatile solvent. Many organic solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform, and diethyl ether, are miscible with it. Ethylene glycol, glycerol, nitromethane, pyridine, and toluene are also miscible. The primary application of ethyl alcohol as a solvent is in the preparation of iodine tinctures, cough syrups, and other pharmaceuticals. Ethyl alcoholalso reacts with light aliphatic hydrocarbons like pentane and hexane, as well as aliphatic chlorides like trichloroethane and tetrachloroethylene.

The miscibility of ethyl alcohol with water is in contrast to the immiscibility of longer-chain alcohols. The chain consists of five or more carbon atoms, and the water miscibility reduces quickly as the number of carbons increases. Below a particular temperature, combinations of dodecane and higher alkanes exhibit a miscibility gap.

Ethanol: human intoxication

Ethanol is an intoxicating substance. When humans consume ethyl alcohol, the liver is unable to purify or filter it all at once. As a result, ethyl alcohol goes to various regions of the body, including the brain and others. When ethyl alcohol enters the brain, it obstructs the spaces that exist between the neurons. People become slow after using ethyl alcohol because their neurons cannot work properly. Their expressions get stained, and their bodies fail to maintain appropriate neuron functioning. Furthermore, drinking alcohol activates the brain’s reward area, causing dopamine to be released. This confuses the brain into believing that ethyl alcoholis beneficial since it makes individuals joyful and energetic. And people continue to consume ethanol.

Some types of ethanol

Industrial ethanol

Industrial alcohol is the alcohol obtained from the fractional distillation of fermented spirits and comprises around 95% ethanol.

Denatured ethanol

Denatured alcohol is alcohol that has been treated with hazardous or unpleasant compounds, rendering it unfit for human consumption. Alcoholic beverages are a significant industry that generates significant tax income. These beverages are significantly taxed in several countries. Because ethyl alcohol has numerous other use, it becomes unfit for drinking in order to lower the tax burden on ethyl alcohol. This is known as denatured alcohol. To denature alcohol, it is coupled with certain bittering or chemicals such as methanol, denatonium benzoate, or pyridine.

Absolute ethanol

The absence of water results in absolute or anhydrous ethyl alcohol. It is almost 99.6% ethanol with a trace amount of another liquid, such as benzene, added to create an azeotropic mixture. Ethyl alcohol dehydration can also be accomplished using molecular sieves. Absolute alcohol is employed as a solvent in situations where water is undesirable or where water can react with other substances. Because water absorbs substantially in the UV range, 100% ethanol is a favored solvent in spectroscopy. This purity grade is also utilized as a fuel additive in petrol. Because ethyl alcohol-containing water will not mix with petrol, the water must be eliminated.

Laboratory test for ethanol

Esterification test: Warming ethanol with anhydrous sodium acetate and concentrated H2SO4 produces ethyl acetate, which has a fruity odor.

Iodoform test: Ethanol reacts with iodine in the presence of potassium hydroxide or sodium hydroxide to give a yellow crystal. This is known as the iodoform reaction. This reaction is used to differentiate ethyl alcohol from methyl alcohol.

Uses of ethanol

  • It is used as a solvent in various organic preparations.
  • Because of its bactericidal and antifungal properties, it is helpful in the medical field as medical wipes and, more popularly, as antibacterial hand sanitizer gels as an antiseptic. Ethanol kills bacteria by dissolving the lipid bilayer in their membranes and denaturing their proteins.
  • It is a common chemical in lotions as a preservative to aid the skin in the cosmetics and beauty products sector.
  • It is utilized as a preservative in paintings since it is an effective solvent, and it is also used in cleaning products to prevent organism breaches.
  • It is used as a color additive as well as for flavor enhancement.
  • Alcohol is utilized in medicine in a variety of ways, including as an antiseptic, disinfectant, and antidote.
  • It can also be found in mouthwashes and used to clean other places. When fomepizole is unavailable, ethyl alcohol is used to treat methanol or ethylene glycol poisoning.
  • In the extraction procedure, ethyl alcohol is also utilized as a solvent.
  • Ethyl alcohol is the primary component of alcoholic beverages. It is, in other words, an intoxicant.
  • It is used in vehicle radiators as an antifreeze.
  • It is used to preserve biological material.
  • It is employed in scientific instruments such as thermometers and spirit levels as a low-freezing and mobile fluid.
  • It is used in petrol to eliminate engine knocking and to keep engines drivable.

References

  1. Morrison, R. T., & Boyd, R. N. (1983). Organic chemistry. Boston: Allyn and Bacon.
  2. Arun Bahl, B.S. Bahl and G.D. Tuli. (1999). Study Guide and Solutions Manual For : Essentials of Physical Chemistry (1). New delhi: S. CHAND.
  3. https://www.britannica.com/science/ethanol
  4. https://www.vedantu.com/chemistry/ethanol.
  5. https://byjus.com/chemistry/ethanol/#:~:text=Ethanol%20is%20a%20plant%20fermentation,an%20additive%20to%20automotive%20gasoline.

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Kabita Sharma

Kabita Sharma, a Central Department of Chemistry graduate, is a young enthusiast interested in exploring nature's intricate chemistry. Her focus areas include organic chemistry, drug design, chemical biology, computational chemistry, and natural products. Her goal is to improve the comprehension of chemistry among a diverse audience through writing.

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