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Hydrocarbon and Its Compounds

Unit: 18

Book Icon Class 10: Science

Hydrocarbon, Types of Hydrocarbons, Homologous Series, Alkyl Radical, Nomenclature of Hydrocarbon, Some Hydrocarbons, Methane, Ethane, Propane, Butane, Alcohol, Alcoholic Compounds, Methyl Alcohol, Ethyl Alcohol, Glycol, Glycerol

Hydrocarbon

The chemical compounds which are made by carbon and hydrogen only are called hydrocarbons. In this organic compound, carbon is tetracovalent, and hydrogen is unicovalent. Methane, Ethane etc. are the examples of hydrocarbons.

 

Types of hydrocarbons

There are two types of hydrocarbons viz. Saturated hydrocarbons and unsaturated hydrocarbons.

1. Saturated hydrocarbons

The hydrocarbons which have a single covalent bond between carbons are called saturated hydrocarbons. It is also called alkanes. The general formula for alkane is CnH2n+2.

Examples:

NameMolecular FormulaCondensed FormulaStructural Formula
MethaneCH4CH4  \[
\begin{array}{c}
\ce{H} \\
| \\
\ce{H-C-H} \\
| \\
\ce{H}
\end{array}
\]
EthaneC2H6H3CCH3  \[
\begin{array}{c}
\ce{H} \quad \ce{H}  \\
| \quad | \\
\ce{H-C-C-H} \\
| \quad | \\
\ce{H} \quad \ce{H}
\end{array}
\]
PropaneC3H8H3CCH2CH3  \[
\begin{array}{c}
\ce{H} \quad \ce{H} \quad \ce{H} \\
| \quad | \quad | \\
\ce{H-C-C-C-H} \\
| \quad | \quad | \\
\ce{H} \quad \ce{H} \quad \ce{H}
\end{array}
\]

2. Unsaturated Hydrocarbons

The hydrocarbons which have two or three covalent bonds between carbons are called unsaturated hydrocarbons. There are two types of unsaturated hydrocarbons viz. Alkene and Alkyne.

a. Alkene

The unsaturated hydrocarbons that have two covalent bonds between carbons are called alkene. The general formula for alkene is CnH2n.

Examples:

NameMolecular FormulaCondensed FormulaStructural Formula
EtheneC2H4  \[
\begin{array}{c}
\ce{H_2-C=C-H_2} \\
\end{array}
\]		  \[
\begin{array}{c}
\ce{H} \quad \ce{H}  \\
| \quad | \\
\ce{H-C-C-H} \\
| \quad | \\
\ce{H} \quad \ce{H}
\end{array}
\]
PropeneC2H6\[
  \begin{array}{c}
   CH_2 = CH_2 \\
   \end{array}
 \]		  \[
 \begin{array}{c}
\ce{H} \quad \ce{H} \\
| \quad | \\
\ce{H-C=C-H} \\
\end{array}
 \]
ButeneC4H8\[
   \begin{array}{c}
   CH_2 = CHCH_2CH_3 \\
   \end{array}
   \]		    \[
   \begin{array}{c}
   \ \text{H} \ \text{H} \quad \text{H} \ \text{H} \\
   | \quad | \quad | \quad | \\
   \ce{H-C=C-C-C-H}\\
   \quad \quad \quad | \quad | \\
   \quad \quad \quad \ce{H} \quad \ce{H} \\
   \end{array}
 \]

b. Alkyne

The unsaturated hydrocarbons which have three covalent bonds between carbons are called alkene. The general formula for alkene is CnH2n-2.

NameMolecular FormulaCondensed FormulaStructural Formula
EthyneC2H2  \[
\begin{array}{c}
\ce{CH#CH} \\
\end{array}
\]		  \[
\begin{array}{c}
\ce{H-C#C-H} \\
\end{array}
\]
PropyneC3H4  \[
\begin{array}{c}
\ce{CH#CHCH_2} \\
\end{array}
\]		    \[
\begin{array}{c}
\quad \quad \quad \ce{H} \\
\quad \quad \quad \ | \\
\ce{H-C#C-C-H} \\
\quad \quad \quad \ | \\
\quad \quad \quad \ce{H} \\
\end{array}
\]
ButyneC4H6  \[
\begin{array}{c}
\ce{CH#CCH_2CH_3} \\
\end{array}
\]		    \[
\begin{array}{c}
\quad \quad \quad \ce{H} \quad \ce{H} \\
\quad \quad \quad | \quad | \\
\ce{H-C#C-C-C-H} \\
\quad \quad \quad | \quad | \\
\quad \quad \quad \ce{H} \quad \ce{H}
\end{array}
\]

 

Homologous Series

A homologous series is a series of hydrocarbons formed under the same general formula. Example: Ether, Alcohol, etc.

 

Alkyl Radical

The group of organic compounds which is formed by removing one hydrogen atom from alkane is called alkyl radical. Examples:

\( \begin{align} CH_4 \xrightarrow{-H} CH_3^+ \text{(Methyl Radical)} \\ C_2H_6 \xrightarrow{-H} C_2H_5^+ \text{(Ethyl Radical)} \\ \end{align} \)

 

Functional Group

An atom or group of atoms that determine the chemical properties of a hydrocarbon is called a functional group. Alkyl radicals combine with functional groups and form different types of organic compounds.

Functional GroupStructureCompounds Formed
Hydroxyl-OHAlcohol
Ether-O-Ether

 

Nomenclature of Hydrocarbon

While naming the hydrocarbons we must follow the following steps:

a. Find Word Root: In the first step, the number of carbons in the hydrocarbons is counted and the word root is defined.

No. of Carbon

Word Root

No. of Carbon

Word Root

1

Meth

6

Hex

2

Eth

7

Hept

3

Prop

8

Oct

4

But

9

Non

5

Pent

10

Dec

 

b. Add Appropriate Suffix: In the second step, the suffix ane (for the single bond), ene (for the double bond), and yne (for the triple bond) are added on the word root.

Conclusion: Word Root + ane/ene/yne

Some Examples:

Q1. What is the IUPAC name of the hydrocarbon C4H10?

- IUPAC stands for International Union for Pure and Applied Chemistry. 

  1. The compound has four Carbons so the word root is “But”.
  2. The Compound matches with the alkane so, the Suffix is “ane”.
  3. Hence, the IUPAC Name of the given hydrocarbon is "Butane". (Word Root + Suffix).

 

Alcohol

The hydrocarbon containing the hydroxyl group(-OH) is called alcohol. The alcohol is formed when the hydroxyl group(-OH) is attached to the alkyl radical. The general formula for alcohol is CnH2n+1OH. Hence, the functional group of alcohol is the hydroxyl group(OH).

\( \begin{align} & \therefore \text{Alkyl Radical} + OH \rightarrow \text{Alcohol} \\ & \text{Eg.} CH_3^+ + OH \rightarrow CH_3OH \text{(Methyl Alcohol)} \end{align} \)

Based on the number of hydroxyls group(OH) the alcohol is classified as: 

a. Monohydric Alcohol: If the alcohol contains a hydroxyl group(OH), then it’s called Monohydric Alcohol. Example: Methyl Alcohol (Methanol)

b. Dihydric Alcohol: If the alcohol contains two hydroxyl groups(OH), then it’s called Dihydric Alcohol. Example: Glycol

c. Trihydric Alcohol: If the alcohol contains three hydroxyl groups(OH), then it’s called Trihydric Alcohol. Example: Glycerol

 

Alcoholic Compounds

1. Methyl Alcohol

\( \begin{array}{c} \ce{H} \\ | \\ \ce{H-C-OH} \\ | \\ \ce{H} \end{array} \)

2. Ethyl Alcohol

\( \begin{array}{c} \ce{H} \quad \ce{H} \\ | \quad | \\ \ce{H-C-C-OH} \\ | \quad | \\ \ce{H} \quad \ce{H} \end{array} \)

3. Glycol

\( \begin{array}{c} \ce{H} \quad \ce{H} \\ | \quad | \\ \ce{H-C-C-H} \\ | \quad | \\ \ce{OH} \quad \ce{OH} \end{array} \)

4. Glycerol

\( \begin{array}{c} \ce{H} \quad \ce{H} \quad \ce{H} \\ | \quad | \quad | \\ \ce{H-C-C-C-H} \\ | \quad | \quad | \\ \ce{OH} \quad \ce{OH} \quad \ce{OH} \end{array} \)

 

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