HALOALKANE AND HALOARENES

Introduction and Classification of Haloalkanes and Haloarenes
Chemistry
June 02, 2023

Haloalkanes and Haloarenes already exist in the environment; surprise? During the Vietnam war, haloarenes were used as herbicides to deplete jungles so that that war would become easy. As they cannot decompose by bacteria, they are still present in the soil. Let us know more about them.

Alkanes are those which have only one covalent bond between carbon atoms, also called saturated hydrocarbons. Whereas alkenes have one or more double or triple covalent bonds between carbon atoms, also referred to as unsaturated hydrocarbons. Haloalkanes and Haloarenes are the Halogen derivatives achieved after replacing hydrogen atoms with halogen atoms.

HALOALKANE 

Haloalkanes are also known as Alkyl halide and halogenoalkanes. Trichloromethane (CHCl3 (chloroform)), Bromoethane (CH3CH2Br), Iodopropane etc are the examples of it. It has existed on earth for centuries; chloroethane is an example, produced in 15th century. Humans produce most haloalkanes, but non-artificial haloalkane also exists, which are produced due to synthesis by bacteria, Seawood, and fungi. Halogen is electronegative, whereas carbon attached to it is electropositive, resulting in an electrophilic carbon, which attracts nucleophiles.

HALOARENES

Haloarenes are also known as halogenoarene or aryl halide. Ocean water has chloride and bromide used by marine organisms to produce aryl halides. At high temperatures, they react with ammonia to produce anilines. Production has been declining since 1980 because of adverse environmental effects. They are aromatic compounds with hydrogen atoms attached to aromatic rings that are substituted by halide. F, Cl, Br, I, and At are the group 17 elements. In between C-Cl and C-F, electronegativity of F is more than Cl.

CLASSIFICATION OF HALOALKANES AND HALOARENES

The classifications are as follows:

  1. Based on hydrogen atoms
  2. Based on Compounds with Sp2 hybridization
  3. Based on Compounds with Sp3 hybridization

BASED ON HYDROGEN ATOMS

They can be mono, di, tri, tetra etc. Their name symbolizes the number of hydrogen atoms contained in their structure.

1. Monohalogen derivatives: Hdrogen atom – 1; General formula - CnH2n+1X; Example -  CH3Cl.

2. Dihalogen derivatives:  Hdrogen atom – 2.

They are of three types named Gem-dihalides, Vic-dihalides, and Terminal halides. Explanations of these are as follows:

  • Gem-dihalides, also known as alkylidene halides, have hydrogen atoms attached to the same carbon atom. Ethylidene chloride, Iso-propylidene bromide, etc., are examples.
  • Vic-dihalides, also termed as alkylene halides, have hydrogen atoms attached to adjacent carbon atoms. Propylene chloride is an example.
  • Terminal halides are called as polymethyl halides, in which hydrogen atoms are attached to terminal carbon atoms. Trimethyl-di-bromide is an example.

3. Trihalogen derivatives: Hdrogen atom – 3; General formula - CnH2n-1X; Example -  1,1,1-trichloropropane

CLASSIFICATION BASED ON NATURE OF CARBON ATTACHED:

Depending on the nature of the carbon atom, Alkyl halides are divided into three types: primary 10, secondary 20, and tertiary 30. Neopentyl Bromide, Secondary-Butyl carbon, and Tertiary-Butyl Bromide are examples, respectively.

BASED ON COMPOUNDS WITH Sp2 HYBRIDIZATION

1. Vinyl halides: The Hydrogen atom is attached to one of the carbon atoms C=C

E.g., CH2=CH-Cl (chloroethene or vinyl chloride)

2. Aryl halides: The Hydrogen atom is attached to carbon in an aromatic ring.

BASED ON COMPOUNDS WITH Sp3 HYBRIDIZATION

  • Alkyl halides: Alkyl chain and hydrogen are attached together to form a compound.
  • Allylic halides: The Hydrogen atom is attached to one of the carbon atoms C=C situated adjacent to Sp2.
  • Benzylic halides: The Halogen atoms are attached to the carbon of the benzene ring.

ISOMERISM OF MONOHALOGEN COMPOUNDS:

  • Chain isomerism is due to different positions of carbon in the alkyl group. 1-chlorobutane and 1-chloro-2-methylpropane have the same chemical formula but different structures.
  • Position isomerism is due to the different arrangement of halogen atoms in the molecule.
  • Optical isomerism is due to asymmetric carbon arrangement. Different- different substituent atoms attached to the carbon.
  • Conformations are formed due to free carbon movement.

 

USES OF HALOALKANES AND HALOARENES

It’s easy to find their use in daily life and industrial purposes. Some of them are the following:

  • It acts as a solvent for non-polar compounds.
  • It is used as a flame retardant and prevents the outbreak of fire. E.g., Carbon tetrachloride in a Fire extinguisher.
  • They are used as propellants.
  • Freons act as cooling substances and are used as refrigerants.
  • Chloramphenicol is used in treating typhoid fever, and Chloroquine in malaria.
  • They are used in DDT as an insecticide.
  • During the synthesis of many organic compounds, They play prime role.
  • Goitre disease is caused due to deficiency of thyroxine, an iodine-based hormone.
  • Iodoform has antiseptic properties, and chloroform has anesthetic.
  • CFC, i.e., chlorofluorocarbons, is labeled as a pollutant as it depletes the ozone layer.

Anatomical species are preserved using them. In short, The organic compounds, i.e., Haloalkenes and Haloarenes, are very useful in everyday life as well as in industries. Haloarenes and haloalkanes of class 12 is an important topic. Haloalkanes and haloarenes NCERT solutions and class 12 chemistry’s haloalkanes and haloarenes notes, written by experts, will be provided to students in the time of their needs. 

DIFFERENCE BETWEEN HALOALKANES AND HALOARENES:

  • C-X bond in Haloalkanes has sp3 hybridization, whereas in Haloalkenes has sp2.
  • Nucleophilic substitution reaction occurs in Haloalkanes and electrophilic substitution reaction in Haloarenes.
  • Haloalkanes are more reactive than Haloarenes.
  • Haloalkanes are soluble in water, but Haloarenes are insoluble. Latter is soluble in organic compounds.
  • Haloarenes have a sweet smell, while Haloalkanes are odorless.
  • Haloalkanes are polar in nature which depends on the electronegativity of halogen.
  • Haloalkanes are hydrocarbons compounds formed from open-chain and are Aliphatic, and the latter are formed from close-chain and are aromatic hydrocarbons.
  • Chloromethane, 1-Bromo-2-methylpropane, etc., are the Haloalkanes examples, and benzyl chloride, iodobenzene, etc., are the Haloarenes examples.
  • Haloalkanes take part in SN2 reaction, but the latter does not.
  • Free radical halogenation is the process that happens in Haloalkanes, whereas the latter has a direct halogenation process.

Halocarbons are widely used nowadays, but some adversely affect our environment by being toxic and pollutants. Methyl bromide and CFC are examples of toxic compounds with no antidot provided. They attack your respiratory system and nervous system. If you want to explore more, we provide online tuition classes for chemistry, where highly qualified teachers make you visualize chemistry and give you real-life examples so that you can easily connect. High-quality course material, interactive sessions, discussions, and Q&As, are the facilities provided to you.

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