10th Chemistry Carbon and its Compounds Notes - Part 01

Carbon and its Compounds Notes

1. The first fullerene was identified to contain 60 carbon atoms in the shape of a football. (C-60). 

Since this looks like the geodesic dome designed by the US architect Buck Minster Fuller, it is named as Buck Minster Fullerene  of molecules through self linking property. This property is called catenation 

2. Carbon combines with oxygen, hydrogen, nitrogen, sulphur, chlorineand many other elements to form various stable compounds. 

3. The stability of carbon compounds is due to the small size of carbon which enables the nucleus to hold on to the shared pair of electrons strongly.

4. Carbon compounds show isomerism : 

The phenomenon by which two or more compounds to have same molecular formula but different structural formula with difference in properties. i.e the formula C2H6O represents two different compounds namely ethyl alcohol (C2H5OH) and di methyl ether (CH3OCH3).

6. The reactions shown by carbon compounds involve breaking of old bonds in the reacting molecules and the formation of new bonds in the product molecules.

7. Carbon compounds are easily combustible.

The electronic configuration of carbon is K=2, L=4. It has four electrons in the valence shell and belongs to group IV A (group 14) of the periodic table.

Carbon is a non metal. In nature, it occurs in its pure form as diamond and graphite. When fuels burn, the carbon in them reacts with oxygen to form carbon dioxide.

Carbon circulates through air, plants, animals and soil by means of complex reactions. This is called carbon cycle.

In the beginning of 19th century scientists classified the compounds of carbon into twotypes, based on their source of occurrence:

i) Inorganic compounds (obtained from non living matter)

ii) Organic compounds (obtained from living matter, such as plant and animal sources) however the basis of classification was subjected to alteration after wohler synthesis

FRIEDRICH WOHLER : A creator of revolution in ORGANIC CHEMISTRY

The term organic chemistry was used by the Swedish chemist Berzelius. This refers to the chemistry of living things. However, the German chemist Wohler succeeded in creating an organic compound (urea) from an inorganic compound (ammonium cyanate) in his laboratory. This has dealt a severe blow to the vital force theory (a theory of life process).

MODERN DEFINITION OF ORGANIC CHEMISTRY

Organic chemistry is defined as the branch of chemistry that deals  with organic compounds which are made up of the hydrocarbons and their derivatives. It gives a thorough insight into the nature of bonding, synthesis, characteristics and their usefulness in various fields

BONDING IN CARBON AND ITS COMPOUNDS

The atomic number of carbon is 6 and its ground state electronic configuration is 1s² 2s² 2p².  
Since it has four electrons in its outermost shell, its valency is four. To achieve noble gas configuration, carbon atom has to lose or gain four electrons to form C ⁴⁺ and C ^4- ions.

1. It could gain four electrons forming C ^4- anion, but it would be difficult for the nucleus with six protons to hold on to ten electrons i.e.four extra electrons.

2. It could lose four electrons to form C ⁴⁺ cations, but it would require a large amount of energy to remove four electrons leaving behind the carbon cations with six protons in its nucleus holding on to just two electrons.

Carbon overcomes this problem by sharing its valence electrons with other atoms of carbon or with atoms of other elements.

This characteristic of carbon atom by virtue of which it forms four covalent bonds is generally referred as tetra valency of carbon.

A molecule of methane (CH₄) is formed when four electrons of carbon are shared with four hydrogen atoms

Fullerenes :   Physical nature of carbon and its compounds

1. Carbon has the ability to form covalent bonds with other atoms of carbon giving rise to large number

5. Carbon compounds have low melting and boiling points because of their covalent nature.

CHEMICAL PROPERTIES

1. Carbon and its compounds burn in oxygen to give carbon dioxide along with heat and light. e.g.,

C + O2 → CO2 + heat + light
CH4 + 2O2 → CO2 + 2H2O + heat + light
C2H5OH + 2O2 → 2CO2 + 3H2O + heat + light

2. Carbon compounds can be easily oxidized using suitable oxidizing agent ( Alkaline potassium ermanganate) to form carboxylic acids.

3. Unsaturated carbon compounds undergo addition reactions with hydrogen in the presence of palladium or nickel catalyst. e.g.,

                            Addition of hydrogen  

CH₂ = CH₂  ------------------------------------>     CH₃ - CH₃  

Ethene                               Ni-catalyst                         Ethane

4. Carbon compounds undergo substitution reactions in the presence of either sunlight or any other reagents. E.g methane undergoes substitution reaction to form different types of products.

5. Carbon compounds such as alcohols react with sodium to liberate hydrogen gas. 
e.g:  2CH₃CH₂OH + 2Na→2CH₃CH₂ONa + H₂

HOMOLOGOUS SERIES

A homologous series is a group or a class of organic compounds having similar structure and similar chemical properties in which the successive compounds differ by a CH2 group.

Characteristics of homologous series

1. Each member of the series differs from the preceding or succeeding member by a common difference of CH2 and by a molecular mass of 14 amu (amu = atomic mass unit).

2. All members of homologous series contain same elements and the same functional groups.

3. All members of homologous series have same general molecular formula.
e.g Alkane =  C_nH _{2n + 2}

     Alkene =  C_nH_2n

    Alkyne =  C_nH_{2n - 2}

4. The members in homologous series show a regular gradation in their physical properties with respect to increase in molecular mass.

5. The chemical properties of the members of the homologous series are similar.

6. All members of homologous series can be prepared by using same general method.

Importance of homologous series

1. It helps to predict the properties of the members of the series that are yet to be prepared.

2. Knowledge of homologous series gives a systematic study of the members.

3. The nature of any member of the family can be ascertained if the properties of the first member are known

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