Hydrocarbons and its Types- Class 12 Chemistry Hydrocarbons Notes

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What are hydrocarbons?

Those organic compounds which are made up of carbon and hydrogen elements only are known as hydrocarbons.

Classification of Hydrocarbons:

Classification of hydrocarbons

Hydrocarbons are classified as:

  1. Open chain Hydrocarbons or Acyclic Hydrocarbons

2. Closed chain Hydrocarbons or Cyclic Hydrocarbons

Explanation:

What are open-chain Hydrocarbons?

The hydrocarbons in which carbon atoms are attached to form open chains are called open-chain hydrocarbons.

Open chain Hydrocarbons may be straight-chain or branched-chain hydrocarbons.

Example of straight-chain hydrocarbon:

CH3-CH2-CH2-CH3

Example of branched-chain hydrocarbon:

Types of Open chain Hydrocarbons:

Open chain Hydrocarbons are of two types:

1. Saturated hydrocarbons ( alkanes or paraffins)

2. Unsaturated hydrocarbons

saturated and unsaturated hydrocarbons

Explanation:

What are saturated hydrocarbons?

Definition:

Hydrocarbons in which all the carbon atoms have a single covalent bond in their molecules are called saturated hydrocarbons.

These are called saturated because their valencies are fully satisfied. Here each carbon is bonded to four other atoms.

Each carbon atom present in saturated hydrocarbons is sp3 hybridized .e.g. alkanes.

They have the general formula CnH2n+2 ( alkanes)

They may be straight-chain or branched-chain hydrocarbons.

Why saturated hydrocarbons are called paraffins?

Saturated hydrocarbons are called paraffins as the word “para” means little and “affin” means affinity or reactivity.

Alkanes are unreactive due to the inertness of a sigma bond and non-polar carbon-carbon or carbon-hydrogen bonds.

For example methane (CH4) .ethane (C2H6) etc.

What are unsaturated hydrocarbons?

Hydrocarbons that contain at least one carbon to carbon double bond or triple bond per molecule are called unsaturated hydrocarbons.

Types of Unsaturated hydrocarbons

  1. Alkene (olefins)
  2. Alkyne (acetylenes)

Alkene:

These are unsaturated hydrocarbons in which at least one carbon to carbon double bond per molecule is present.

They have the general formula CnH2n (alkenes)

They may be straight-chain or branched-chain.

Carbon to carbon double bond is sp2 hybridized in alkenes.

Why alkenes are called olefins?

Alkenes are unsaturated hydrocarbons in which at least one carbon to carbon double bond per molecule is present. These are called olefins because “oleum“ means oil and “facere” means to make (oil-making substances).

Lower members of alkenes e.g. ethane form oily liquids on reaction with Cl2 gas.

Alkyne:

These are unsaturated hydrocarbons in which at least one carbon to carbon triple bond per molecule is present.

They have the general formula CnH2n -2(alkynes)

They may be straight-chain or branched-chain.

Carbon to carbon triple bond is sp hybridized in alkynes.

Closed Chain Hydrocarbons (Cyclic Hydrocarbons):

These are the hydrocarbons in which carbon atoms are attached in the form of a ring or cycle.

That’s why closed chain hydrocarbons are also known as cyclic hydrocarbons.

Types of Closed Chain Hydrocarbons:

These are of two types:

1. Alicyclic hydrocarbons

2. Aromatic hydrocarbons

Explanation:

Alicyclic hydrocarbons:

Alicyclic hydrocarbons

Alicyclic hydrocarbons have 2 hydrogen atoms less than their corresponding open-chain hydrocarbons.

Their general formula is CnH2n.

Why alicyclic hydrocarbons are called non-benzenoid cyclic hydrocarbons?

Alicyclic hydrocarbons are called non-benzenoid cyclic hydrocarbons because they do not have a benzene ring in their structure.

Aromatic hydrocarbons:

Aromatic hydrocarbons

Aromatic hydrocarbons are compounds in which all carbon atoms present in the ring are sp2 hybridized.

The term Aroma was introduced by Kekule. Aroma means smell/fragrance.

Kekule wanted to classify benzene and its derivatives. It was observed that many of the derivatives of benzene had aroma (smell), that’s why they are called aromatic compounds.

Example of Aromatic hydrocarbon:

Benzene is the simplest aromatic hydrocarbon. Benzene has a regular hexagonal structure with alternate single bond and double bonds in their structure.


Types of Hydrocarbons Chemistry Class 12 ( Urdu / Hindi )

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1 thought on “Hydrocarbons and its Types- Class 12 Chemistry Hydrocarbons Notes”

  1. Thanks for another excellent post. Where else may just anyone get that type of info in such a perfect means of writing? I’ve a presentation next week, and I am at the look for such info.

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