Hydrocarbon: chemistry

Unsaturated Hydrocarbons: Alkenes

Hydrocarbons with multiple bond between carbon – carbon atoms are called Unsaturated Hydrocarbons.

Unsaturated hydrocarbons means hydrogen atoms are not saturated in such compounds and more hydrogen atom can be added to them.

On the basis of number of bonds present, Unsaturated Hydrocarbons can be further divided into two groups:

(a) Alkenes and (b) Alkynes

(a) Alkenes

Hydrocarbon with double bond between carbon–carbon atoms are called Alkenes. Alkenes has lack of two hydrogen atoms to saturate the compound.

Alkane – ane + ene = Alkene

General Formula of Alkene

The general formula of Alkene = C _n H_{2 n}

Where n is the number of carbon atoms.

(1) When n = 1

Therefore, C _n H_{2 n}

= C ₁ H_{2 × 1}

= C ₁ H ₂

This molecule does not exist, because there are minimum two carbon atoms necessary to form an Unsaturated Hydrocarbon.

Thus, (2) When n = 2

Therefore, C _n H_{2 n}

= C ₁ H_{2 × 2}

= C ₂ H ₄

Since, Alkane having two carbon atoms is called Ethane

Thus, Ethane – ane + ene = Ethene

Thus, name of alkene having two carbon atom is Ethene.

General name of Ethene is Ethylene.

Structure Formula of Ethylene or Ethene (C₂H₄) is

(3) When n = 3

Therefore, C _n H_{2 n}

= C ₃ H_{2 × 3}

= C ₃ H ₆

Since, the name of hydrocarbon having three carbon is Propane.

Therefore, Propane – ane + ene = Propene

And, hence name of Alkene having three carbon atom is Propene

The structural formula or Propene is

(4) When, n = 4

Therefore, C _n H_{2 n}

= C ₄ H_{2 × 4}

= C ₄ H ₈

Since, the name of Alkane having four hydrocarbon is Butane

Thus, Butane – ane + ene = Butene

Thus, the name of Alkene having four hydrocarbon is Butene

The general name of Butene is Butylene. And the structural formula of Butene (C₄H₈) is

(5) When, n = 5

Therefore, C _n H_{2 n}

= C ₅ H_{2 × 5}

= C ₅ H ₁₀

Since, the name of alkane having five carbon atom is Pentane

Thus, Pentane – ane + ene = Pentene

Thus, the name of alkene having five carbon atom is Pentene

The structural formula of Pentene is

(6) When n = 6, therefore,

C _n H_{2 n}

= C ₆ H_{2 × 6}

= C ₆ H ₁₂

The name of this alkene having six carbon atoms is

Hexane – ane + ene = Hexene

Structure formula of Hexene is

(7) When n = 7, therefore,

C _n H_{2 n}

= C ₇ H_{2 × 7}

= C ₇ H ₁₄

The name of this alkene having seven carbon atoms is

Heptane – ane + ene = Heptene

The common name for Alkene having seven carbon atoms is Heptylene

Structure formula of Heptene or heptylene is

(8) When n = 8, therefore,

C _n H_{2 n}

= C ₈ H_{2 × 8}

= C ₈ H ₁₆

The name of this alkene having eight carbon atoms is

Octane – ane + ene = Octene

The common name for Alkene having eight carbon atoms is Octylene

Structure formula of Octene or Octylene is

(9) When n = 9, therefore,

C _n H_{2 n}

= C ₉ H_{2 × 9}

= C ₉ H ₁₈

The name of this alkene having nine carbon atoms is

Nonane – ane + ene = Nonene

The common name for Alkene having nine carbon atoms is Nonylene

Structure formula of Nonene or Nonylene is

(10) When n = 10, therefore,

C _n H_{2 n}

= C ₁₀ H_{2 × 10}

= C ₁₀ H ₂₀

The name of this alkene having ten (10) carbon atoms is

Decane – ane + ene = Decene

The common name for Alkene having ten (10) carbon atoms is Decylene

Structure formula of Decene or Decylene is

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