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CBSE NOTES ⇒ Class 10th ⇒ Science ⇒ 4. Carbon and its Compounds

4. Carbon and its Compounds

Hydrocarbons


Hydrocarbons


Hydrocarbons: All carbon compounds which contain just carbon and hydrogen are called hydrocarbons.

                  

Formulae of organic compounds:

(i) General formula: General formula represents a function for n numbers of each atom in a molecule. 

Example: for alkane: CnH2n+2

(ii) Molecular formula: Molecular formula represents actual number of atoms of a molecule. 

Example: For Ethane: C2H6

(iii) Condensed formula: Condensed formula represents group of atoms linked together to each carbon atom. 

Example: For Ethane: CH3CH3

(iv) Structural formula: It represents exact arrangement of atom of a molecule. 

Example: For Ethane: 

(v) Electronic formula: Electronic formula represents the sharing of electrons amongs atoms of a molecules. 

Example: For Ethane: 

Saturated Carbon Compounds: 

Compounds of carbon, which are linked by only single bonds between the carbon atoms are called saturated compounds.

Example: Alkanes like methane, Ethane, propane butane etc.

General formula for Alkanes: CnH2n+2

Using formula for Methane;

CnH2n+2

Putting n =1 we get

C1H2x1 + 2

CH4

Similarily; 

For Ethane:

Putting n =2 we get

C2H2x2 + 2

C2H6

Similarily we can find molecular formula for propane, butane, pentane and so on ....... 

Alkanes: The saturated hydrocarbons in which carbon atom linked together with single bond are called alkenes.

 Name of Alkanes Molecular Formula  Condensed structural Formula 
Methane  CH4 CH4
Ethane C2H6 CH3CH3
Propane C3H8 CH3CH2CH3
Butane  C4H10 CH3CH2CH2CH3
Pentane  C5H12 CH3CH2CH2CH2CH3
Hexane  C6H14 CH3CH2CH2CH2CH2CH3
Heptane C7H16 CH3CH2CH2CH2CH2CH2CH3
Octane  C8H18 CH3CH2CH2CH2CH2CH2CH2CH3
Nonane  C9H20 CH3CH2CH2CH2CH2CH2CH2CH2CH3
Decane C10H22 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Structure of Methane (single bond);

      

Single carbon atom has four unsatisfied valency Linked with Hydrogen atom like figure. 

                                               

Electrone Dot strucuture of Methane

 

Structure of Ethane (single bond);

  C - C [ carbon atoms linked together witha single bond] 

Next Linked with Hydrogen atom to carbon unsatisfied valency like given figure;  

             

                             

Electron Dot structure of Ethane 

Structure of propane (single bond);

Structure of Butane (single bond);

Structure of pentane (single bond);

Structure of hexane (single bond);

Unsaturated Carbon Compounds: 

Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated compounds.

Example: Alkenes like and Alkynes;

Structure of alkenes (Double bond);

General Formula for Alkenes: CnH2n

The simplest Alkenes is Ethene;

So Ethene has 2 carbon atoms; 

Now putting n = 2 in general formula;

C2H2x2 = C2H4

Propene has 3 carbon atoms;

Now putting n = 3 in general formula;

 C3H2x3 = C3H6

Similarily we can find the molecular formula for other Alkenes like butene, pentene and hexene etc.

Alkenes: The unsaturated hydrocarbons which contain one or
more double bonds are called alkenes.

 Name of Alkenes Molecular Formula  Condensed structural Formula 
     
Ethene C2H4 CH2=CH2
Propene C3H6 CH3CH=CH2
Butene  C4H8 CH3CH2CH=CH2
Pentene  C5H10 CH3CH2CH2CH=CH2
Hexene  C6H12 CH3CH2CH2CH2CH=CH2
Heptene C7H14 CH3CH2CH2CH2CH2CH=CH2
Octene  C8H16 CH3CH2CH2CH2CH2CH2CH=CH2
Nonene  C9H18 CH3CH2CH2CH2CH2CH2CH2CH=CH2
Decene C10H20 CH3CH2CH2CH2CH2CH2CH2CH2CH=CH2

Structural Formula of Alkene: 

 Name of Alkenes Molecular Formula  Structural Formula 
     
Ethene C2H4
Propene C3H6
Butene  C4H8
Pentene  C5H10
Hexene  C6H12
Heptene C7H14
Octene  C8H16
Nonene  C9H18
Decene C10H20

Electron Dot Sructure of Ethene: 

    

              Ethene (C2H4)

Electron Dot Sructure of Propene: 

                        Prooene (C2H4)

Similarily We can draw electron dot structure of other Akenes; 

Structure of Alkynes (Triple Bond):

General formula of Alkynes: CnH2n-2

The simplest alkynes is Ethyne;

Ethyne has two carbon atoms. Hence, Using the formula;

Putting n = 2 for Ethyne,

C2H2x2-2 = C2H2

  ∴ Ethyne = C2H2

Similarily we can find Propyne; 

Putting n=3 for Propyne; 

C3H2x3-2 = C3H4

  ∴ Propyne = C3H4

Alkynes: 

 Name of Alkenes Molecular Formula  Condensed structural Formula 
     
Ethyne C2H2 CH≡CH
Propyne C3H4 CH≡CCH3
1-Butyne  C4H6 CH≡CCH2CH3
1-Pentyne  C5H8 CH≡CCH2CH2CH3
1-Hexyne  C6H10 CH≡CCH2CH2CH2CH3
1-Heptyne C7H12 CH≡CCH2CH2CH2CH2CH3
1-Octyne  C8H14 CH≡CCH2CH2CH2CH2CH2CH3
1-Nonyne  C9H16 CH≡CCH2CH2CH2CH2CH2CH2CH3
1-Decyne C10H18 CH≡CCH2CH2CH2CH2CH2CH2CH2CH3

Long chain formula is abbreviated as bellow;

[Nonyne] CHCCH2CH2CH2CH2CH2CH2CH3 can be written as  

CHC (CH2)6CH3

similarily;

[Decyne] CH≡CCH2CH2CH2CH2CH2CH2CH2CH3 can be written as 

CH≡C (CH2)7CH3

Defferences between saturated and unsaturated carbon compound:

          Saturated Compound          Unsaturated Compound

1. It has single bond between carbon atoms.

2. There occurs substitution reaction in it.

3. Example: Alkanes.

4. They are less reactive than the unsaturated carbon compound. 

1. It has double and triple bond between carbon atoms.

2. There occurs addition reaction in it.

3. Example: Alkenes, Alkynes.

4. They are more reactive than the saturated carbon compounds.

 

 

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Study Materials List:

CBSE NOTES ⇒ Class 10th ⇒ Science
1. Chemical Reactions and Equations
2. Acids, Bases and Salts
3. Metals and Non-metals
4. Carbon and its Compounds
5. Periodic Classification of Elements
6. Life Processes
7. Control and Coordination
8. How do Organisms Reproduce
9. Heredity and Evolution
10. Light-Reflection and Refraction
11. Human Eye and Colourful World
12. Electricity
13. Magnetic Effects of Electric Current
14. Sources of Energy
15. Our Environment
16. Management of Natural Resources

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