What is ethylene glycol in organic chemistry?

 

Ethylene glycol or glycol, also known as ethane-1, 2-diol, is the simplest dihydric alcohol with molecular formula C2H6O2. It is a colorless, odorless viscous liquid which has a sweet taste.

The IUPAC name of ethylene glycol is ethane-1,2-diol. But it is also known as 1,2-dihydroxyethane, monoethylene glycol, hypodicarbonous acid, ethylene alcohol etc.

 

It is predominantly used for two purposes. One is the production of polyester fibers and the other as the raw material for antifreeze formulations.

The melting point of ethylene glycol is 260.2 K and the boiling point is 470 K. The high boiling point of ethylene glycol is due to formation of hydrogen bonding with water molecule.

Ethylene glycol is a polar compound. Because of it contains two polar O – H bond. For this reason, it is miscible in all proportions with polar solvent water and ethanol.

The density of ethylene glycol solution is 1.11 g/ ml. Ethylene glycol is a moderately toxic alcohol.

Read more : Is methane a greenhouse gas?

 

What is the chemical formula and structure of ethylene glycol?

 

The chemical formula of ethylene glycol is C2H6O2. Molecular formula shows that it contains two carbon atoms, six hydrogen atoms and oxygen atoms.

 

Each carbon atom in ethylene glycol is directly attached with two hydrogen atoms and one oxygen atom.

 

Both the carbon atoms are sp3 hybridized. Each oxygen atom contains two lone pair of electrons and they are also sp3 hybridized.

 

How is ethylene glycol made?

 

There are different methods for the preparation of ethylene glycol. Few methods for the preparation of ethylene glycol are discussed below.

 

Ethylene glycol from ethylene

 

When ethylene is passed into cold dilute alkaline permanganate solution, ethylene glycol is obtained. This is an example of cis-hydroxylation.

 

H2C = CH2 + H2O + [O] ⟶ CH2 (OH)-CH2 (OH)

 

Again, ethylene glycol is also produced by passing ethylene into HOCl acid followed by hydrolysis by boiling with aqueous NaHCO3.

 

H2C = CH2 + HOCl ⟶ Cl-CH2-CH2-OH ⟶ HO-CH2-CH2-OH + NaCl + CO2

 

Ethylene glycol from ethylene dibromide

 

Ethylene glycol may be prepared by boiling of ethylene dibromide with aqueous sodium carbonate.

 

Br-CH2-CH2-Br + Na2CO3 + H2O ⟶ HO-CH2-CH2-OH + 2NaBr + CO2

 

Ethylene glycol from ethylene oxide

 

Ethylene glycol is prepared industrially by treating ethylene oxide with dilute hydrochloric acid. So it is very important method.

 

 

What is ethylene glycol used for?

 

Ethylene glycol is widely used as an organic solvent. It is also used as an antifreeze agent and as a raw material in the manufacture of polyesters such as polyethylene terephthalate.

 

Ethylene glycol is used in automobiles and liquid-cooled computers as an important medium of heat transfer. Ethylene glycol is commonly used as a coolant for cold-water air conditioning systems.

 

In geothermal heating / cooling systems, ethylene glycol is a liquid that transfers heat using geothermal heat pumps.

 

The mixture of ethylene glycol with water provides additional benefits to coolant and antifreeze solutions, such as preventing corrosion and acid degradation, as well as inhibiting the growth of most microbes and fungi.

 

What is ethylene glycol antifreeze agent?

 

Pure ethylene glycol freezes at about 12 ᵒC, but when mixed with water the mixture freezes at low temperatures.

 

Because of pure ethylene glycol has a specific heat capacity about one half that of water. For example, a mixture of 60% ethylene glycol and 40% water freezes at −45 °C (−49 °F).

 

Mixture of ethylene glycol and water can also be chemically termed as glycol concentrate/compound/mixture/solution.

 

The use of ethylene glycol not only depresses the freezing point of aqueous mixtures, but also elevates their boiling point.

 

This results in the operating temperature range for heat-transfer fluids being broadened on both ends of the temperature scale.

 

The increase in boiling temperature is due to pure ethylene glycol having a much higher boiling point and lower vapor pressure than pure water, as is typical with most binary mixtures of volatile liquids.

 

Precursor to polymers

 

In the plastic industry, ethylene glycol is an important precursor to polyester fibers and resins. Polyethylene terephthalate, which prepared from ethylene glycol, is used to make plastic bottles for soft drinks.

 

Chemical reactions

 

Ethylene glycol is used to prepare a large number organic compounds, such as ethylene dibromide, ethylene dibromide, ethylene, glycolic acid, oxalic acid, ethane dial etc.

               

Ethylene glycol reacts with aldehyde or ketone to hemiacetal or acetal compounds. Besides, ethylene glycol is used as a protecting group for carbonyl groups in organic synthesis.

 

Treating a ketone or aldehyde with ethylene glycol in the presence of an acid catalyst gives the corresponding a 1,3-dioxolane, which is resistant to bases and other nucleophiles.

 

Other uses of ethylene glycol

 

Dehydrating agent

 

Ethylene glycol is used in the natural gas industry to remove water vapor from natural gas before further processing.

 

Hydrate inhibition

 

Ethylene glycol is a useful desiccant due to its high boiling point and affinity for water. Ethylene glycol is widely used to inhibit the formation of natural gas clathrates in long multiphase pipelines that convey natural gas from remote gas fields to a gas processing facility.

 

Natural gas is dehydrated by ethylene glycol. In this application, ethylene glycol flows down from the top of a tower and meets a rising mixture of water vapor and hydrocarbon gases.

 

Applications of ethylene glycol

Minor uses of ethylene glycol include the manufacture of capacitors, as a chemical intermediate in the manufacture of 1,4-dioxane, as an additive to prevent corrosion in liquid cooling systems for personal computers, and inside the lens devices of cathode-ray tube type of rear projection televisions.

 

Ethylene glycol is also used in the manufacture of some vaccines. It is used as a minor ingredient in shoe polish and also in some inks and dyes.

 

It has been used in a few cases to treat partially rotted wooden objects to be displayed in museums.

 

Ethylene glycol is commonly used as a preservative for biological specimens, especially in secondary schools during dissection as a safer alternative to formaldehyde.

 

It is also used as part of the water-based hydraulic fluid used to control subsea oil and gas production equipment.

 

Ethylene glycol is used as a protecting group in organic synthesis to protect carbonyl compounds such as ketones and aldehydes. It also can be used in vaccine manufacture or as a formaldehyde substitute when preserving biological specimens. 

 

 

Is ethylene glycol toxic?

 

Ethylene glycol is not highly toxic alcohol.It is moderately toxic for human.But the biggest danger is because of its sweet taste, which can attract children and anima.

 

After ingestion, ethylene glycol is first oxidized to glycolic acid and then to oxalic acid, which is toxic.

 

It and its toxic byproducts first affect the central nervous system, then the heart, and finally the kidneys. Ingestion of sufficient amounts is fatal if untreated.

 

 

• What is ethylene glycol in organic chemistry?
• What is the chemical formula and structure of ethylene glycol?
• How is ethylene glycol made?
• What is ethylene glycol used for?
• What is ethylene glycol antifreeze agent?
• Is ethylene glycol toxic?

 

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