Halogen Atoms Along the Chain of Carbon Atoms

In the periodic table, the halogen atom is positioned in the 17th group of the periodic table. The halogen elements shown in this group are Fluorine, Chlorine, Bromine, Iodine, Tennessine, and Astatine. Now, these particular elements are used as atoms in a chain of carbon atoms or, that is, what we call carbon compounds containing Halogens.

So, Halogen Derivatives are compounds in which an equal number of halogen atoms are substituted in place of hydrogen atoms of a hydrocarbon. Halogen derivatives of alkanes are called haloalkanes. In alkyl halides, the halogen atom and carbon atom are held together by forming a single covalent bond. 

 Halogen Atom Position Meaning or Carbon compound containing Halogen:

The carbon atom in the hydrocarbons with hydrogen atoms attached to it is replaced by a halogen atom, one of these elements,  F, Cl, Br, or I. These new compounds formed, which have halogen elements attached to them, are known as haloalkanes and haloarenes. We call them halogen derivatives, and these particular derivatives do not occur naturally. Therefore, they are synthesised in the laboratory. They are widely used for industrial and domestic uses. Uses such as industrial solvents, which are used in the production of pharmaceuticals. There are many other uses, such as a dry cleaning agent, an anaesthetic in medicine, a pesticide, etc. 

The compound whose molecules contain one halo group (Cl 一 or Br 一 or I 一 or F 一) directly linked to alkyl chain are known as alkyl halides or mono halogen derivatives of alkanes. Depending upon the carbon atom (that is 1०, 2०, 3०) which contain the halogen atom. The alkyl halides can be primarily divided into three types based on the position of the halogen atom along the chain of carbon, viz., primary, secondary and tertiary halides. They are represented by the formula RX or 

CnH2n+1X

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where X  一 is the halo group. For example, 1-Chloropropane  CH3CH2CH2Cl

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Haloalkanes are called mono, di, tri, tetra etc., depending upon the halogen atom position, that is, when molecules contain one, two, three, four etc., halogen atoms in the molecules, respectively. The halogen atom position causes variation in the properties of the haloalkanes, such as solubility of the haloalkane, boiling points and character of the bonds. 

Isomerism in Alkyl Halides

Alkyl Halides shows the following three types of isomerism. 

1. Chain Isomerism:

This type of Isomerism is due to differences in the arrangement of carbon atoms in the chain. The first three members do not exhibit this but are shown only by higher members. So, in this type of Isomerism, the halogen atom position remains unchanged. 

For Example: 

The chain isomer of  1-Chlorobutane  is 

1-Chloro-2-methylpropane 

 Position Isomerism:

In this type of Isomerism, isomers differ in the position of the halogen atom. So, the halogen atom position changes. 

For Example: 

The position isomer of  1-Chlorobutane  is 

2-Chlorobutane

 Optical Isomerism:

This type of Isomerism is exhibited by alkyl halides having a chiral structure (molecules having non-superimposable mirror images). So, in this case, the halogen atom position changes along with the hydrocarbons molecules. 

For Example,

2-chlorobutane exhibits enantiomerism, and the two enantiomers are:

Enantiomers of 2-chlorobutane

Classification of Alkyl Halides or Haloalkanes:

Haloalkanes can be divided into three classes based on halogen atom position on the chain of carbon atoms. 

1. Primary Haloalkanes:

Primary haloalkanes are the compounds in which the halogen atom is directly combined with one alkyl group. So, the halogen atom is combined with the CH₂  group that holds the halogen atom through a single bond except for CH₃Br and other methyl halides as there is no alkyl group in which halogen is attached to CH₂ group.

For Example:

 Secondary Haloalkanes:

Secondary haloalkanes are the alkyl halides in which the halogen atom is positioned to other two alkyl groups along the chain of carbon atoms to two other alkyl groups. These alkyl groups combine the same or different types of the alkyl group. 

For Example:

3. Tertiary Haloalkanes:

Tertiary haloalkanes are the alkyl halides in which the halogen atom is positioned to three alkyl groups along the chain of carbon atoms to two other alkyl groups. These alkyl groups combine the same or different types of the alkyl group. 

For Example:

Conclusion:

Here, we learned that the alkyl halides are the compounds that contain a halogen atom along the chain of the alkyl group. The study of halogen atom position and the properties of the halogen atom present in the alkyl halide is of immense importance, as it decides different Physical properties such as Melting and Boiling points (for isomeric alkyl halides boiling points decreases as the branching increases, For the same halogen, boiling points decreases as the size of the alkyl group increases), Density, Bond strength, Dipole moments, Stability and Solubility.