Carbon & Its Compounds By- A.P.S. Bhadouriya, M.Sc. B.Ed., CSIR-NET

Carbon: Introduction Atomic Number: 6 Electronic configuration: 2, 4 Valence electrons: 4 , Property: Non-metal

Abundance: Carbon is the 4th most abundant substance in universe and 15th most abundant substance in

the earth’s crust.

Compounds having carbon atoms among the components are known as carbon compounds. Previously,

carbon compounds could only be obtained from a living source; hence they are also known as organic

compounds.

Bonding In Carbon: Covalent Bond Bond formed by sharing of electrons is called covalent bond. Two of more atoms share electrons to make

their configuration stable. In this type of bond, all the atoms have similar rights over shared electrons.

Compounds which are formed because of covalent bond are called COVALNET COMPOUNDS.

Covalent bonds are of three types: Single, double and triple covalent bond.

Single Covalent Bond: Single covalent bond is formed because of sharing of two electrons, one from

each of the two atoms.

Formation of hydrogen molecule (H2) Atomic Number of H = 1 Electronic configuration of H = 1

Valence electron of H = 1

Hydrogen forms a duet, to obtain stable configuration.

This configuration is similar to helium (a noble gas).

Since, hydrogen has one electron in its valence shell,

so it requires one more electron to form a duet.

So, in the formation of hydrogen molecule;

one electron from each of the hydrogen atoms is shared.

Formation of hydrogen chloride (HCl): Valence electron of hydrogen = 1

Atomic number of chlorine = 17

Electronic configuration of chlorine: 2, 8, 7

Electrons in outermost orbit = 7Valence electron = 7

Formation of chlorine molecule (Cl2): Valence electron of chlorine = 7

Formation of water (H2O)

Valence electron of hydrogen = 1

Atomic number of oxygen = 8

Electronic configuration of oxygen = 2, 6

Valence electron = 6

Oxygen in water molecule completes stable configuration by

the sharing one electron from each of the two hydrogen atoms.

Formation of Methane (CH4)Formation of Ethane (C2H6):

Valence electron of carbon = 4

Valence electron of hydrogen = 1

Double covalent bond: Double bond is formed by sharing of four electrons, two from each of the

two atoms.

Formation of oxygen molecule (O2):

Valence electron of oxygen = 2

In the formation of oxygen molecule,

two electrons are shared by each of the two oxygen atoms to complete their stable configuration.In

oxygen, the total number of shared electrons is four, two from each of the oxygen atoms. So a double

covalent bond is formed.

Formation of Carbon dioxide (CO2):

Valence electron of carbon = 4

Valence electron of oxygen = 6

In carbon dioxide two double covalent bonds are formed.

Formation of Ethylene (C2H4):

Valence electron of carbon = 4

Valence electron of hydrogen = 1

Triple Covalent Bond: Triple covalent bond is formed because of the sharing of six electrons, three

from each of the two atoms.

Formation of Nitrogen (N2):

Atomic number of nitrogen = 7

Electronic configuration of nitrogen = 2, 5

Valence electron = 5

In the formation of nitrogen, three electrons are shared by each of the

nitrogen atoms. Thus one triple bond is formed because of the sharing of

total six electrons.

Formation of Acetylene (C2H2):

Properties of Covalent Bond:

Intermolecular force is smaller.

Covalent bonds are weaker than ionic bond. As a result, covalent compounds have low melting

and boiling points.

Covalent compounds are poor conductor of electricity as no charged particles are formed in

covalent bond.

Since, carbon compounds are formed by the formation of covalent bond, so carbon compounds

generally have low melting and boiling points and are poor conductor of electricity.

Organic Compounds

Initially, compounds of carbon could only be obtained from living sources and there was no way of

synthesizing them. Hence, carbon compounds are also known as organic compounds.

Versatile Nature Of Carbon- Carbon forms a large number of compounds. So far, formulae of

about 3 million carbon compounds are known.

Cause of formation of such a large number of compounds by carbon:

a. CATENATION- Carbon can form bonds with other carbon atoms. This property of carbon

is known as catenation. Because of catenation, carbon can form a long chain; while

making bond with other carbon atoms. Carbon can make single, double and triple bonds by

catenation.

Carbon can form branched chain; along with straight chain; while combining with carbon

atoms, i.e. because of the property of catenation.

Example:

b). TETRAVALENCY OF CARBON - having a valency of 4 carbon can also form bonds with other

types of monovalent atoms; apart from carbon. Carbon can make long chain combining with other atoms

also. For example; carbon can form bonds with oxygen, hydrogen, nitrogen, etc.e.g. CH3-Cl , CH3-

OH , CCl4 , CH3-COOH etc.

Carbon-carbon bonds are very stable, which makes the compounds of carbon stable.

Hydrocarbons- (Hydrogen + Carbon = Hydrocarbon) Compounds formed by the combination of hydrogen and carbon are

known as hydrocarbons. There are two types of hydrocarbon, viz. saturated hydrocarbon and unsaturated

hydrocarbon.

Saturated hydrocarbons: Hydrocarbons having single bonds are known as SATURATED

HYDROCARBONS. Saturated hydrocarbons are known as ALKANE. These are also known as paraffin.

Example: Methane, Ethane, Propane, etc.

Unsaturated hydrocarbon: Hydrocarbons having C=C bonds and C≡C bonds are known as

UNSATURATED HYDROCARBONS.

Hydrocarbons having at least one double bond are known as ALKENE. Example: CH2=CH2 Ethylene,

CH3CH=CH2 Propylene etc.

Hydrocarbons having at least one triple bond are known as ALKYNE. Example: CH≡CH Ethyne,

CH3C≡CH Propyne, CH3CH2C≡CH Butyne, etc.

Alkane : Hydrocarbons having only single bonds are known as alkane. These are saturated hydrocarbons.

Alkane are also known as paraffin. The general formula of alkane is CnH2n+2 here ‘n’ is the No. of Carbon

atoms. If C = 1 then CnH2n+2 = C1H2x1+2 = CH4

:

Alkene: Hydrocarbons having at least one double bond

between two carbon atoms are known as ALKENE. General

formula of alkene is CnH2n. .Minimum two carbon atoms are

required to form alkene.If C = 2 then CnH2n = C2H2x2 = C2H4.

.Alkyne: Hydrocarbons having at least one triple bond between two carbon atoms are known as alkyne

General formula of alkyne is CnH2n − 2. Minimum two carbon atoms are required to form alkyne. If C = 2,

then; CnH2n − 2 = C2H2x2 − 2 = C2H2 (H-C≡C-H )The name of this compound is ethyne.

Cyclic Hydrocarbon:

Carbon can form cyclic structure combining with carbon atoms. Such hydrocarbons are known as cyclic

hydrocarbon. Structural formulae of some of the cyclic hydrocarbons are as follows:

Functional Group: Single atom (other than carbon and H)or group of atoms, which is responsible for specific chemical

properties of the compound, regardless of the length and nature of the carbon chain are called functional

groups. The functional group is attached to the carbon chain through this valency by replacing one hydrogen

atom or atoms. Some functional groups are as follows-

Halogen group: Halogen group is also known as halo group. −Cl (Chloro),−Br(Bromo),−I(Iodo) are

halogen or halo group.

Alcohol: −OH is known as alcohol group.

Aldehyde: −CHO is known as aldehyde group. Its structural formula is as

follows:

Ketone Group: −CO− is known as ketone group. This is also known as

carbonic group. Its structural formula is as follows:

Carboxylic Acid Group: −COOH is known as carboxylic acid group; or

simply as acid group. Its structural formula is as follows:

Homologous Series: Series of compounds with same general formula and functional group is known as homologous series.

Compounds belonging to the same homologous series show similar properties. Compounds of homologous

series differ by CH2 from their consecutive members. Each subsequent compound in a homologous series

differs by 14 u in mass.

Example: Alkanes; such as, Methane, Ethane, Propane, Butane, etc. belong to same homologous series. Properties of Compounds of Same Homologous Series

a. Compounds of same homologous series have same general formula.

b. Compounds of same homologous series differ from their consecutive members by one carbon atom

and two hydrogen atoms, homologous series differ from their consecutive members by one carbon

atom and two hydrogen atoms, i.e. by CH2

c. Compounds of same homologous series have same chemical properties.

d. Compounds of same homologous series differ by physical properties with increase or decrease in

molecular mass.

Nomenclature of Carbon compounds : International Union of Pure and Applied Chemistry (IUPAC) decided some rules to name the carbon compounds. This was done to maintain the uniformity throughout the world. Names which are given on this basis are popularly known as IUPAC name. The rules for nomenclature are as follows:

1.Identify the number of carbon atoms in carbon compound. Name the carbon compounds according

to the number of carbon atoms.

2. If the structure has branched chain, identify the longest chain and then identify the number of

carbon atoms.

3. Identify the longest chain. Then number the carbon

atoms in such a fashion that the functional group;

if any; would come at the lowest number.

4.In case of a functional group present, write the prefix or suffix of the functional group according to

the table given here. Then write the name of the parent compound.

prefix

Word root

Primary suffix

Secondary suffix Used for side chain and substituent groups

Indicates No. of carbon atoms in carbon parent chain

Indicates carbon parent chain saturation/ unsaturation that is nature of C-C bonds

Indicates principle functional group

Fuctional group Sec. suffix

R- alkyl C1 - meth All C-C bonds are single

bond or only one carbon

atom in molecule

ane

Carboxylic acid

R-COOH

oic acid CH3- methyl C2 - eth

CH3CH2- Or -C2H5

-Ethyl

C3 - prop Ester

R-COOR

oate CH3CH2CH2- propyl C4 - but One C=C present

ene

Aldehyde

R-CHO

al Cl - chloro C5 - pent

Br - Bromo C6 - hex Ketone

R-CO-R

one I- iodo C7 -hept Two C=C present

adiene F- fluoro C8 -oct Alcohol

R-OH

ol NO2- nitro C9 - non One C≡C present

yne -OR - alkoxy C10 - dec Amines

R-NH2

amine Cn - alk

Note- if name of secondary suffix starts with a vowel the terminal e from ane / ene / yne is removed off.

Some important compounds with their IUPAC Name and common name(within brackets)

(CH3-CH2-CH2-CH3)

{CH3-CH(CH3)-CH3}

(CH3-CH2-CH2-Cl

(CH3-OH)

(CH3-CH2-OH)

Butane 2-methyl propane

(isobutane)

1-chloro propane

(n-propyl chloride)

Methanol

(methyl alcohol)

Ethanol

(ethyl alcohol)

(HCHO)

(CH3-CHO )

( HCOOH)

(CH3-CO-CH3 )

(CH3-COOH )

Methanal

(formaldehyde)

Ethanal

(acetaldehyde)

Methanoic acid

(formic acid)

Propanone

(acetone)

Ethanoic acid

(acetic acid)

(CH3-CH(OH)-CH3 )

( C5H10 )

2,3-dimethyl

pentane Propan-2-ol

(iso-propyl alcohol)

cyclopentane Benzene Methyl benzene

(toluene)

ISOMERISM:

The phenomenon of existence of two or more compounds possessing the same molecular formula but

different properties is known as isomerism. Such compounds are called as isomers.

Structural Isomerism

Compounds having the same molecular formula but different structures (manners in which atoms are linked)

are called as structural isomers. For example

C5H12 represents three compounds

C3H8O represents three compounds

CH3-CH2-O-CH3

Ethyl methyl ether

(Methoxy methane )

CHEMICAL PROPERTIES OF CARBON COMPOUNDS

(a).Combustion: Carbon, in all its allotropic forms, burns in oxygen

to give carbon dioxide along with the release of heat

and light.

Saturated hydrocarbons will generally give

a clean flame while unsaturated carbon compounds

will give a yellow flame with lots of black smoke

Why do substances burn with or without a flame? A flame is only produced when gaseous substances burn. When wood or charcoal is ignited, the volatile

substances present vapourise and burn with a flame in the beginning. A luminous flame is seen when the

atoms of the gaseous substance are heated and start to glow. The colour produced by each element is a

characteristic property of that element.

(b).Oxidation: Carbon compounds can be easily oxidised

on combustion. e.g.

CH4 + 2O2 CO2 + 2H2O + heat energy

In addition to this complete oxidation, we

have reactions in which alcohols are converted to carboxylic acids –

(c).Addition Reactions: Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give

saturated hydrocarbons. This reaction is called hydrogenation.This reaction is commonly used in the hydrogenation of vegetable oils (to prepare vegetable ghee) using a nickel catalyst.e.g.

CH2=CH2 + H2 + (Nickel catalyst) ⇨ CH3−CH3

Catalysts Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction itself being affected. For example- Pt, Pd, Ni, Fe, Cu are most commonly used catalyst.

(d).Substitution Reactions: In a substitution reaction one type of atom or a group of atoms takes the place of another. Saturated

hydrocarbons generally undergo substitution reactions. e.g. Chlorine can replace the hydrogen atoms one by

one in the presence of sunlight.

CH4 + Cl2 → CH3Cl + HCl (in the presence of sunlight)

SOME IMPORTANT CARBON COMPOUNDS:

ETHANOL Production:

1.Ethanol can be produced by the fermentation of sugars

and starches from many different sources

2. It can be synthesized by hydration of alkene (ethene) in the presence of suitable catalyst (conc. H2SO4

/P2O5/Al2O3).

Properties of Ethanol : 1.Ethanol is a liquid at room temperature .

2.Ethanol is commonly called alcohol and is the active ingredient of all alcoholic drinks.

3.Ethanol is also soluble in water in all proportions.

4. In addition, because it is a good solvent, it is also used in medicines such as tincture iodine,

cough syrups, and many tonics.

Reactions of Ethanol:

(i) Reaction with sodium –

When ethanol reacts with sodium, it gives sodium ethoxide and hydrogen gas.

2CH3CH2OH + 2Na ⇨ 2CH3CH2ONa + H2

This reaction shows the acidic nature of ethanol

(ii) Reaction to give unsaturated hydrocarbon: Dehydration

Ethanol gives ethene and water when it is heated with concentrated sulphuric acid.

CH3CH2OH

CH2=CH2 + H2O

The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water

from ethanol.

(iii) Oxidation of ethanol: Ethanol gives ethanoic acid on oxidation.

CH3CH2OH + (Alkaline KMnO4/Acidified K2Cr2O7) ⇨ CH3COOH

How do alcohols affect living beings?

Ethanol: When large quantities of ethanol are consumed, it tends to slow metabolic processes and to

depress the central nervous system. This results in lack of coordination, mental confusion, drowsiness,

lowering of the normal inhibitions, and finally stupour.

The individual may feel relaxed but does not realise that his sense of judgement sense of timing, and

muscular coordination have been seriously impaired.

Methanol: Intake of methanol in very small quantities can cause death. Methanol is oxidised to methanal in the liver.

Methanal reacts rapidly with the components of cells. It causes the protoplasm to get coagulated, in much

the same way an egg is coagulated by cooking. Methanol also affects the optic nerve, causing blindness.

Denatured alcohol:

To prevent the misuse of ethanol produced for industrial use, it is made unfit for drinking by adding

poisonous substances like methanol to it. This is called denatured alcohol. Dyes are also added to colour the

alcohol blue so that it can be identified easily.

ETHANOIC ACID( CH3COOH):

Ethanoic acid is commonly called acetic acid andbelongs to a group of

acids called carboxylic acids.

Ethanoic acid freezes in winter and hence it is also known as glacial acetic acid.

Ethanoic acid is a colorless liquid.5% to 8% solution of acetic acid in water is known as

vinegar.Vinegar is used as preservative in pickles.

Carboxylic acids are weak acid compared to mineral acids.

Reactions of ethanoic acid:

1. Reaction with a base -It react with a base to give salt and water

NaOH + CH3COOH → CH3COONa + H2O

2.Reaction with carbonates and hydrogen carbonates: Ethanoic acid reacts with carbonates and hydrogen carbonates to give rise to a salt, carbon dioxide

and water.

CH3COOH + NaHCO3 → CH3COONa + H2O + CO2

2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

2. Esterification reaction: Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester,it is

called as esterification reaction.

CH3COOH + C2H5OH ⇨ CH3COOC2H5 + H2O

Ethyl acetate (Ethyl ethanoate)

Esters are sweet-smelling substances. These are used in making perfumes and as flavouring

agents.

3.Saponification:

Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid or its salt.

This reaction is known as saponification because it is used in the preparation of soap.

CH3COOC2H5 + NaOH → CH3COONa + C2H5OH

SOAPS AND DETERGENTS

Soap: Sodium or potasium salt of higher

fatty acids (long-chain carboxylic

acids) are called soap.

Natural soaps are prepared by boiling

lard or other animal fat with NaOH, in a

reaction called saponification (Latin,

sapo, soap). The sodium salt so formed

has cleansing property.

Cleansing action of soap:

Soap molecule has two ends. One end is hydrophilic and another end is hydrophobic. In other words,

one end is lipophobic (hydrophilic) and another end is lipophilic (hydrophobic). When soap is dissolved

in water and clothes are put in the soapy solution, soap molecules converge in a typical fashion to make a

structure; called micelle. The hydrophobic ends of different molecules surround a particle of grease and

make the micelle; which is a spherical structure. In this, the hydrophilic end is outside the sphere and

hydrophobic end is towards the centre of the sphere. That is how, soap molecules wash away dirt and

grease by making micelles around them.

Micelle: A spherical arrangement of organic molecules in water clustered so that their hydrophobic parts are

buried inside the sphere and their hydrophilic parts are on the surface of the sphere and in contact with water

Soap and Hard Water: Hard water often contains salts of calcium and magnesium. Soap molecules react

with the salts of calcium and magnesium and form a precipitate. This precipitate begins floating as an off-

white layer over water. This layer is called scum. Soaps lose their cleansing property in hard water because

of formation of scum.

Detergent: Soap cannot form lather in hard water. To

overcome this problem, detergents were introduced. Detergent

is also known as soapless soap. Detergent is sodium salt of

benzene sulphonic acid or sodium salt of long chain alkyl

hydrogen sulphate. The charged ends of these compounds do

not form precipitate with calcium or magnesium salts in hard

water. Hence, detergents retain their cleansing property in hard water.

Sodium soaps

1,2,3-Propanetriol(Glycerol; Glycerin)

A triglyceride(a triester of glycerol)

+

saponification+CH

CH2 OCR

CH2 OCR

CHOH

CH2 OH

CH2 OH

RCO 3 NaOH

3 RCO- Na

+

O

O

O

O