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What is Polyhalogen Compounds?

The hydrocarbons or any carbon compounds containing more than one halogen atom (group 17 elements of the modern periodic table) are known as polyhalogen compounds.

Many of these compounds are useful in industry and agriculture. Some notable polyhalogen compounds are described below:

1. Trichloromethane (Chloroform), CHCl3


Chloroform, also referred to as trichloromethane is an organic compound. Chloroform is an organic chemical compound initially employed as an ideal anaesthetic. It was first prepared in 1831. The chemical formula is CHCl3. It is a colourless, sweet-smelling dense liquid produced on a large scale.

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Uses of Chloroform:

  1. Used as an anaesthetic and used in dentistry during root canal procedures.
  2. The spectrum of pure chloroform is used as the reference or background, and pure cholesterol powder or cholesterol extract from milk products is dissolved in chloroform and used for FTIR analysis.
  3. Chloroform was utilized in the past as an extraction dissolvable for fats, greases, oils, and different items; as a laundry spot.
  4. Used as an indirect food additive in food packaging materials for adhesive components and as a component of food contact materials.

2. Dichloromethane, CH2Cl2

Dichloromethane is a geminal organic compound and is also called Methylene chloride or Methylene dichloride. It can be obtained naturally from oceanic sources, macroalgae, volcanoes, and wetlands. The majority of Methylene dichloride in the environment is due to industrial emissions. The chemical formula of Dichloromethane is CH2Cl2.

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Uses of Dichloromethane:

  1. Dichloromethane is used as a solvent in food technology
  2. It is used in aerosol formulations.
  3. It is an ethane foam blowing agent.
  4. Used as a solvent in the manufacturing of pharmaceutical products.
  5. CH2Cl2 is used as a degreasing agent.
  6. Used in the manufacturing of electronics.

3. Iodoform

Iodoform which is also called triiodomethane is a yellow crystalline solid. It is insoluble in water but soluble in solvents like ethanol, chloroform, and ether. It is hydrolyzed to give sodium methanoate (sodium formate) when treated with an aqueous sodium hydroxide solution.

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Uses of Iodoform:

Iodoform was used earlier as an antiseptic but the antiseptic properties are due to the liberation of free iodine and not due to the iodoform itself. Due to its objectionable smell, it has been replaced by other formulations containing iodine.

Question for Polyhalogen Compounds
Try yourself:What is the reason for iodoform to be used as an antiseptic?
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4. Tetrachloromethane (Carbon Tetrachloride)

  • It is a colourless liquid with a “sweet” smell that can be detected at low levels. The molecular formula of carbon tetrachloride is CCl4.
  • It is used in the manufacturing of refrigerants, as a cleaning agent and was also used as a fire extinguisher.
  • Medically, it is one of the most potent hepatotoxins (toxic to the liver) and is widely used in scientific research to evaluate hepatoprotective agents.
  • When carbon tetrachloride is released into the air, it rises in the atmosphere and depletes the ozone layer. Depletion of the ozone layer is believed to increase human exposure to ultraviolet rays, leading to increased skin cancer, eye diseases and disorders, and possible disruption of the immune system.

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Question for Polyhalogen Compounds
Try yourself:The oxidation of trichloromethane results in the formation of a poisonous gas called ________
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5. Freons (CFCs)

  • Freons are the chlorofluorocarbon compounds of methane and ethane. The chlorofluorocarbon compounds refer to the compounds having mainly carbon, fluorine, and chlorine. Freons is the brand name for this group of compounds coined by DuPont.
  • They are extremely stable, unreactive, non-toxic, non-corrosive and easily liquefiable gases.
  • Freon 12 or R-12 (CCl2F2) is one of the most common representatives of this group. It is manufactured from tetrachloromethane by Swarts reaction.
  • These are usually produced for aerosol propellants, refrigeration and air conditioning purposes.

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Question for Polyhalogen Compounds
Try yourself:Which of the following is not a freon?
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6. DDT (p, p’-Dichlorodiphenyltrichloroethane)

  • It is a colourless, crystalline, tasteless and almost odourless organochloride known for its insecticidal
  • It was the first chlorinated organic insecticides prepared in 1873. But in 1939, Paul Miller identified the different uses of DDT. Paul Muller was awarded the Nobel Prize in Medicine and Physiology in 1948 for this discovery.
  • It became popular because of its effectiveness against the mosquito that spreads malaria and lice that carry typhus.
  • But due to the ill-effects of DDT such as chemical instability and fat solubility, it got banned in many countries

Polyhalogen Compounds | Chemistry for JEE Main & Advanced

Question for Polyhalogen Compounds
Try yourself:Which of the following polyhalogen compounds in useful in extinguishing fires?
View Solution

The document Polyhalogen Compounds | Chemistry for JEE Main & Advanced is a part of the JEE Course Chemistry for JEE Main & Advanced.
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FAQs on Polyhalogen Compounds - Chemistry for JEE Main & Advanced

1. What are polyhalogen compounds?
Ans. Polyhalogen compounds are chemical compounds that contain multiple halogen atoms. Halogens are a group of elements that include fluorine, chlorine, bromine, iodine, and astatine. Polyhalogen compounds can have two or more halogen atoms bonded together in the same molecule.
2. What are some examples of polyhalogen compounds?
Ans. Some examples of polyhalogen compounds include carbon tetrachloride (CCl4), iodine pentafluoride (IF5), bromine trifluoride (BrF3), and chlorine trifluoride (ClF3). These compounds consist of multiple halogen atoms bonded together with other elements.
3. What are the properties of polyhalogen compounds?
Ans. The properties of polyhalogen compounds depend on the specific compound but generally include high reactivity, volatility, and toxicity. Polyhalogen compounds often have strong oxidizing or reducing properties and can be used as solvents, refrigerants, or chemical intermediates.
4. What are the uses of polyhalogen compounds?
Ans. Polyhalogen compounds have various uses in different industries. For example, carbon tetrachloride (CCl4) has been used as a fire extinguishing agent, degreaser, and solvent. Iodine pentafluoride (IF5) is used in the synthesis of organic compounds, while chlorine trifluoride (ClF3) is used as a rocket propellant and in the production of semiconductors.
5. What are the health and environmental concerns associated with polyhalogen compounds?
Ans. Polyhalogen compounds can pose health risks if not handled properly. Many of them are toxic and can cause harm through inhalation, ingestion, or skin contact. Some polyhalogen compounds are also persistent in the environment and can contribute to air and water pollution. Proper safety measures and disposal methods should be followed when dealing with these compounds.
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