CHAPTER 01
Carbon and It's
Compounds
In this Chapter...
!
Hydrocarbons
!
Covalent Bonding in Carbon
Compounds
!
Isomerism
!
Allotropes of Carbon
!
Functional Groups
! Organic Compounds
! Homologous Series
Carbon is the third most important element after oxygen and
● It could lose 4 electrons and form C4+ cation. But a large
hydrogen, for the existence of life on the Earth. The Earth
amount of energy is required to remove 4 electrons
crust has only 0.02% carbon which is present in the form of
leaving behind a carbon cation with 6 protons in its
minerals (like carbonates, hydrogen-carbonates, coal,
nucleus holding on just two electrons together, which is
petroleum, etc.) and the atmosphere has 0.03% of carbon
not possible.
dioxide.
In order to overcome this problem, carbon shares its
Fuels (like wood, kerosene, coal, LPG, CNG, petrol, etc.)
valence electrons with other atoms of carbon or with atoms of
clothing material (like cotton, nylon, polyester, etc.), paper,
other elements.
rubber, plastics, leather, drugs and dyes are all made up of
These shared electrons belong to the outermost shells of
carbon.
both atoms and in this way, both atoms attain the nearest
noble gas configuration. This type of bonding is called
Covalent Bonding in Carbon Compounds
covalent bonding.
The bonds which are formed by the sharing of an electron pair
Compounds having covalent bonds are called covalent
between the atoms (either same or different atoms) are known
compounds, these are generally poor conductor of
as covalent bonds.
electricity.
Atomic number of carbon (C) is 6.
K
L
Examples of Covalent Bonding
So, its electronic configuration =
,
2
4
Some example depicting of covalent bonding are as follows
Thus, there are 4 electrons in its outermost shell and its octet
can be completed by the following two ways
1. Formation of Methane (CH )
4
● It could gain 4 electrons and form C4− anion. But for a
In the formation of a methane molecule, one carbon atom
nucleus having 6 protons, it would be difficult to hold on 10
shares its 4 electrons with four hydrogen atoms (one electron
electrons, i.e. 4 extra electrons.
of each hydrogen atom). It shows carbon is tetravalent
because it possesses 4 valence electrons and hydrogen is
● Fullerenes are recently discovered allotropic forms of
monovalent because it has only 1 valence electron.
carbon which were prepared for the first time by HW
Before
After
Kroto, Smalley and Robert Curt by the action of laser beam
Shared
combination
combination
on the vapours of graphite.
Electrons
H
H
H
Versatile Nature of Carbon
H
C
H
H
C
H
or H—C—H
Main factors that are responsible for the formation of large
number of carbon compounds are
H
H
H
(i) Catenation The property of self linking of elements mainly
Methane (CH )
4
molecule
C-atoms through covalent bonds to form long, straight or
branched chains and rings of different sizes is called
2. Formation of Water Molecule (H O)
2
catenation. Carbon shows maximum catenation in the
Atomic number of O = 8
periodic table due to its small size and strong C ⎯ C bond.
K L
Electronic configuration =
(ii) Tetravalency of carbon The valency of carbon is four, i.e.
2,
6
it is capable of bonding or pairing with four other carbon
Atomic number of H = 1
atoms or with the atoms of some other monovalent
K
Electronic configuration =
elements like hydrogen, halogen (chlorine, bromine), etc.
1
To attain the stable electronic configuration of the nearest
(iii) Tendency to form multiple bonds Carbon has a strong
noble gas, hydrogen needs 1 electron and oxygen needs
tendency to form multiple bonds due to it’s small size. It
2 electrons. So, two hydrogen atoms share an electron pair
shares more than one electron pair with its own atoms or
with the atoms of elements like oxygen, nitrogen,
with the oxygen atom such that hydrogen acquires a duplet
sulphur, etc.
configuration and oxygen an octet, resulting in the
formation of two single covalent bonds.
Organic Compounds
Before
After
combination
combination Shared electrons
The compounds of carbon except its oxides, carbonates and
hydrogen carbonate salts, are known as organic compounds.
H
O
H
H
O
H or H — O —H
In 1828, German chemist Friedrich Wohler accidently
prepared urea from ammonium cyanate when he was trying to
Water (H O)
2
molecule
prepare ammonium cyanate by heating ammonium sulphate
and potassium cyanate. Thus, synthesis of urea discarded the
Properties of Covalent Compounds
vital force theory.
The compounds containing covalent bonds are called
Hydrocarbons
covalent compounds. They have following properties i.e.
Organic compounds made up of carbon and hydrogen are
● Covalent compounds have low melting and boiling points
called hydrocarbons. These are of two types, i.e.
due to small intermolecular forces of attraction between the
atoms.
1. Aliphatic Saturated Hydrocarbons
● Covalent compounds are generally poor conductors of
Saturated aliphatic hydrocarbons are called alkane or paraffin.
electricity. This is because the electrons are shared
All the carbon atoms in these are bonded through single bonds.
between atoms and no charged particles are formed in these
compounds.
The general formula of these compounds is C H
n 2n+ 2 andsuffix
“-ane” is used in their nomenclature.
● Covalent compounds are generally volatile in nature.
e.g. CH4 (methane), C H
2
6
(ethane), etc.
Allotropes of Carbon
2. Aliphatic Unsaturated Hydrocarbons
Allotropy is the property by virtue of which an element exists
Those compounds in which at least one double or triple bond
in more than one form and each form has different physical
is present between two carbon atoms are called unsaturated
properties but identical chemical properties. These different
hdyrocarbons.
forms are called allotropes. Carbon exists in different
Aliphatic unsaturated hydrocarbons are of two types
allotropic forms; some of them are diamond, graphite and
fullerene.
(i) Alkene Those hydrocarbons which have at least one
● Diamond is a colourless transparent substance and very
carbon-carbon double bond are called alkenes or olefins.
The general formula of these compounds is C H
hard whereas graphite is an opaque substance which have
n 2n,
e.g. C H
(ethene).
smooth surface and slippery to touch.
2
4
(ii) Alkyne Those hydrocarbons which must have at least
To satisfy it, a double bond is used between the two carbon
one carbon-carbon triple bond are called alkynes. The
atoms.
H
H
general common formula of these compounds is
C H
e.g. C H
(ethyne).
C==C
[Step III]
n 2n− 2 ,
2
2
H
H
Structure of Saturated and Unsaturated
Now, all the four valencies of carbon are satisfied.
Compounds
Electron dot structure of ethene
Steps to draw the structure of carbon compound are
H
H
Step I. First connect all the carbon atoms together with a
single bond.
C
C
Step II. After that use the hydrogen atoms to satisfy the
H
H
remaining valencies of carbon (as carbon forms 4
bonds due to its 4 valency).
3. Structure of Ethyne (C H )
Step III. If number of available H-atoms are less than what is
2
2
required, satisfy the remaining valency by using
Link the two carbon atoms by single bond.
double or triple bond.
C—C
[Step I]
1. Structure of Propane (C H )
Link the two hydrogen atoms with unsatisfied valencies of
3
8
carbon.
Same rules are followed here as in case of ethane. Here, the
three carbon atoms are linked together with a single bond.
H ⎯C ⎯ C ⎯H
[Step II]
C—C—C
[Step I]
But in this case even after linking the available hydrogen
atoms with carbon atoms, still two valencies of each carbon is
To satisfy the remaining valencies of carbon atoms, hydrogen
unsatisfy. To satisfy it, a triple bond is used between the two
atoms are linked with them.
carbon atoms.
H
H
H
⏐
⏐
⏐
H ⎯C ≡≡C ⎯ H
[Step III]
H—C—C—C—H
[Step II]
In ethyne, the two carbon atoms share three pairs of
⏐
⏐
⏐
electrons among themselves to form a carbon-carbon triple
H
H
H
bond.
2 carbon atoms are bonded to 3 hydrogen atoms and 1 carbon
Each carbon atom shares one electron with each hydrogen
atom is bonded to 2 hydrogen atoms.
atom to form two carbon-hydrogen single bonds.
Electron dot structure of propane
Electron dot structure of ethyne
H
H
H
H
C
C
H
H
C
C
C
H
Structure of Cyclic Compounds
H H H
In some compounds, carbon atoms are arranged in the form
2. Structure of Ethene (C H )
2
4
of ring. e.g. cyclohexane (C H
)and benzene (C H )
6
12
6
6 .
Link the two carbon atoms by single bond.
H
C—C
[Step I]
H
H
C
Link the four hydrogen atoms with carbon atom to satisfy the
C
H
H
H—C
C—H
unsatisfied valencies of carbon.
C
C
H
H
H
H
H
H
H—C
C—H
C
C
!
H
H
"C—C
[Step II]
C
! "
C
H
H
H H
H
But in this case, even after linking the available hydrogen
C6H6
C6H12
atoms with carbon atoms, still one valency of each carbon
(Cyclohexane)
(Benzene)
remains unsatisfy.
Names and Formulae of Functional Group
Isomerism
Name of functional group
Formula of functional group
Organic compounds with same molecular formula but
different chemical and physical properties are called
Alcohol
— OH
isomers. This phenomenon is called isomerism.
Aldehyde
O
The difference in properties of these compounds is due to
⏐⏐
the difference in their structures. These compounds have
— CHO or ⎯C
⎯
H
identical molecular formula but different structures. Hence,
Ketone
O
they are called structural isomers and phenomenon is
⏐⏐
called structural isomerism.
⎯C ⎯
Carboxylic acid
O
e.g. Two structural isomers are possible for butane (C H
)
4
10 .
⏐⏐
H
⎯C⎯O ⎯H
H
H
H
H
H
H
C
H
Thus, — OH in methyl alcohol (CH OH)and —COOH
H
C C C
C H
H
C C
3
(carboxylic acid) in formic acid (H⋅COOH) are present as
C
H
H
H
H
H
H H
functional groups.
H H
Straight chain structure
Branched chain structure
Homologous Series
A series of similarly constituted compounds in which the
Functional Groups
members present have the same functional group and similar
chemical properties and any two successive members in a
Groups which combine with a carbon chain and decide its
particular series differ in their molecular formula by a
chemical properties are called functional groups.
⎯CH2— unit, is called a homologous series.
e.g.
— OH in R—OH will decide the chemical properties
e.g. CH , C H ,
4
2
6
C H ,C H
3
8
4
10 arethemembersofalkane
of this compound, thus it is a functional group.
family.
