Chemistry

Topic : Some basic concepts in chemistry

What is Chemistry :-

Chemistry is defined as the study of the

composition, structure and properties of matter

and the reactions by which one form of matter

may be converted into another form.

Types of Chemistry :-

i. Physical chemistry : The branch of

chemistry that deals with the structure of

matter, the energy changes and the

theories, laws and principles that explain

the trantormation of matter from one form

to another.

ii. Inogranic chemistry : This is the branch

of chemistry that deals with chemistry of

elements other than carbon and of their

compounds.

iii. Organic chemistry : This is the branch

of chemistry that deals with the reactions

of the compounds of carbon.

iv. Analytical chemistry : This is the branch

of chemistry dealing with the separation,

identification and quantitative

determination of the compositions of

different substances.

v. Biochemistry : This is the chemistry of

the substances consisting of living

organisms.

(Pharamaceutical, environmental, nuclear

are also some more branches of

chemistry.)

Application of Chemistry :-

i) Food : Trees and plants photosynthesise

food in presence of sunlight. Green colouring

matter chlorophyll acts as photosensitizer

(catalyst). The process is a simple chemical

reacton.

CO2 + H2O food grain / fruits/flowers

/ cotton /medicine etc.

This reaction takes place in nature. Till today

we are not in position to carry out this simple

reaction in our laboratories. However, the

development of good quality fertilizers and

increased have increased the yield.

ii) Energy : The major sources of energy are

fossil fuels like coal, petroleum, natural gas

etc. These are all combustible chemicals. The

fuels are burnt to produce energy to drive trains,

trucks, buses and all automobiles. However,

burning of fuel increases constantly

environmental pollution and is responsible for

global warming.

Researches in the field of electrochemistry,

have developed several electrochemical cells

like, Daniel cell, lead storage cell, dry cell,

nickel cadminum cell, lithium ion cell fuel cell.

Now the attempt is being made to convert

solar energy into electrical energy using photo

valataic cells, the solar cells.

iii) Drugs : This includes manufacture of

droug L-dopa used for treatment of parkinsons

disease. Synthesis of human insulin used for

treatment of diabetes.

Tamiflue is the medicine developed to treat

the patients suffering from swine fule.

Hopefully, the research in the field of mechanism

of ageing will give longer, healthier and happier

life span for the entrie world population.

Nature of Matter :

A mixture is a simple combination of two or

more substance in which the constituent

substances retain their separate identities.

Mixture of ethyl alcohol and water, salt and

water or mixture of gases, air constitute a

homogeneous mixture. For a given

homogeneous mixture the concentrations of

the constituents remain uniform throughout

the mixture and ll the constituents are present

in one phase.

If two or more phases are present in a mixture

then it is called a heterogeneous mixture. For

example, phenol-water system, silver

chloride-water system, iron filling-sand

system, etc.

Mixture of all gases constitute homogeneous

system while mixture of all solids constitute

heterogeneous system.

Mixture of liquids may be homogeneous or

heterogeneous.

The phlogiston theory :

The theory stated that, a substance

undergoing combustion mainly constants a

mysterious matter called phlogiston and some

clax.

If a substance is burnt, phlogiston evolves and

goes into the atmosphere and clax is left

behind as an ash.

When candle burns in closed container, the air

in container becomes saturated with

phlogiston.

Elements and compounds : All pure

substances are classified as either elements or

compounds. An elements is defined as a

substance that cannot two or more different

substances. Some of the examples of elements

known for long time are gold, silver, coper,

carbon, sulphur and phosphorous. Till recent

times, 118 elements are indentified. Most of the

elements exist naturally and a few of the

elements are man made.

Compounds are defined as substances of

definite compositions which can be decomposed

into two or more substances by a simple

chemical process.

Chemists represent elements by symbols of

one or two letters.

The Arbitrarily decided and universally

accepted standards are called units.

Any measured property is expressed as a

number along with an appropriate unit

associated with the property.

While making calculations it is advisable to

confine to one single system of unit.

NASA’s Mars climate orbiter, the first

weather satellite for Mars was destroyed by

heat.

Law of conservation of mass : The law states

that the mass is neither created nor destroyed

during chemical combination of matter.

Consider burning of carbon.

Carbon + oxygen carbon dioxide

According to law of conservation of mass, the

sum of masses of carbon and oxygen i.e, sum of

masses of the reactants is always equal to mass

of product carbon dioxide formed during the

reaction.

Law of definite composition : The law was

stated by French chemist Joseph Proust. The

law states that any pure compound always

contain the same elements in a definite

proportion by weight irrespective of its source

or method of preparation. The law is also

called law of definite proportions.

Law of multiple proportions : The law states

that, if two elements chemically combine with

each other forming two or more compounders

with different compositions by weight then the

masses of two interacting elements in the two

compounds are in the ratios of small whole

numbers.

On analysis it was found that, 1g of carbon

reacts with 1.33 g of oxygen to form carbon

monoxide and 1 g of carbon reacts with 2.66 g of

oxygen to yield carbon dioxide. Hence the ration

of weights of oxygen to that of carbon for two

compounds are ,

For carbon dioxide,

= 2.66

For carbon monoxide,

= 1.33

Hydrogen interacts with oxygen to form two

compounds water and hydrogen peroxide. On

analysis it is found that water contains 88.89%

by weight of oxygen and 11.11% by weight of

hydrogen. Therefore the ratio of percentage

by weight of oxygen to that of hydrogen is

equal to.

Gay Lussac’s law of combining volumes of

gases : When gases react together to produce

gaseous products, the volumes of reactants and

products bear a simple whole number ratio

with each other, provided volumes are

measured at same temperature and pressure.

Dalton’s Atomic Theory : The tiny small,

indivisible particles of matter were called

atoms.

i) All matters are made up of tiny,

indestructible, indivisible unit particles

called atoms. Atoms are the smallest

particles of the elements and molecules are

the smallest particles of a compound.

ii) All atoms of the same element have same

size, shape and mass and all other

properties. Atoms of different elements

have different properties.

iii) Compounds are formed when atoms of

different elements combine. The atoms in a

compound unite in small whole number

ratio like 1: 1, 1:2, 1:3, 2:1, 2:3,etc.

iv) A Chemical reaction involves only the

separation combination or rearrangement of

interger number of atoms. During chemical

reaction atoms are neither created nor

destroyed.

With these assumptions Dalton explained

law of conservation of mass.

Law of multiple proportion was explained

by Dalton by assuming that under some

conditions atoms of two types combine in

the ratio 1 : 1 to form a molecule. Under

some different conditions it may combine in

the ratio 1 : 2 or 1 : 3 or 2 : 3, etc.

1 gram molar mass is also called 1 gram

Concepts of Elements, Atoms and Molecules :

The smallest indivisible particle of an element is

called an atom. Every atom of an element has a

definite mass of the order of 10-26

kg and has a

spherical shape of radius of the order of 10-15

m.

Atomic and Molecular Masses :

Every atom of an element consists of fixed

number of protons, neutrons and electrons, the

subatomic particles. The number of protons

varies from atom to atom. The mass of the atom

changes as the number of subatomic particles is

changed. Hence masses of different atoms of

different elements are different. The size of

single atom is of the order of 10-15

m and the

mass is of the order of 10-26

kg. Hence it is not

possible to weight a single atom. However it is

possible to determine masses of the atoms of the

elements relative to mass of some standard

element experimentally (using mass

spectrograph). The standard element chosen is

assigned appropriate value of mass of an atom.

By international agreement in 1961 fro

determining atomic masses, carbon-12 a distinct

atom of carbon was chosen as standard with its

atomic mass 12.000 atomic mass unit

abbreviated as amu. The masses of all other

atoms are determined relative to the mass of an

atom of carbon-12, the standard. Recently the

unit of atomic mass amu is replaced by u meaing

unified mass.

Average atomic mass :

Isotopes are the atoms of the same elements

having same atomic number containing same

number of protons and electrons but different

number of neutrons hence possess different

mass numbers. Many naturally occurring

elements exist in the form of two or more

isotopes. The observed atomic mass of the atom

of the elements is the average atomic mass of

the elements taking into consideration the

natural abundances of the isotopes. The natural

abundance means per-centage occurrence. The

mass spectrometer with higher precision shows

variation of exact atomic mass of the isotope of

the elements with its relative abundance.

Molecular mass (Molar mass) :

Molar mass of a substance is defined as the

ration of mass of one molecule of a substance

to 1/12th

of mass of one atom of Carbon-12.

It is also the algebraic sum of atomic masses

of constituent atoms which constitute the

molecule.

molecule or 1 gram mole or simply 1 mole.

1 mole of the elements means amount of the

element equal to its atomic mass in gram and

also called 1 gram atom of the element or 1

mole of the element.

Avogadro’s Law :

Lussac’s law and Dalton theory to propose

Avvogadro’s law.

It states that, equal volumes of all gases under

identical conditions of temperature and

pressure contain equal number of molecules.

Avogadro’s law is stated as, at constant

pressure and temperature volume of a gas is

directly proportional to number of molecules.

V number of molecules (P, T constant) .

But, number of molecules n, the number of

moles of gas

Hence, V n

Or

= constant

Where number of moles, n =

At STP, it may be possible to calculate volume

per mole

of an ideal gas. According to

general gas equation, PV = nRT Hence, at STP

R = 0.08205 L atmosphere mol

-1K

-1.

Atomicity of a gas molecule :

Atomicity of a molecule is the total number of

atoms of constituent elements combined to

form a molecule.

Mole concept and Avogadro number :

The quantity of a substance equal to its

atomic mass or molar mass in gram is referred

as 1 mole of the substance.

As present in 0.012 kg of Carbon-12.

This number of particles is determined to be

equal to 6.022 x 1023

particles.

This is the number of atoms, molecules, ions,

electrons present in 1 mole of a substance.

This number of electrons makes an electrical

charge of one Faraday.

PROBLEM :

PROBLEM :

Calculate the number of moles and molecules

present in 0.032 mg of methane (C=12, H=1)

Solution: Molecular mass of methane, CH4 = 12

+4 = 16 g mol-1

16 g of methane = 1 g mole.

Therefore,0.032 mg = 3.2x 10-5

g methane

=

= 2 x 10

-6 mole methane

Now, 1 mole of methane = 6.022 x 1023

molecules of methane

Hence 2 x 10-6

mole of methane = 12.044 x

1017

molecules of methane.

Percentage Composition and Molecular

Formula : The molecular formula indicates the

actual number of constituent atoms in a

molecule. Molecular formula is integral multiple

of empirical formula.

Chemical Reactions and Stoichiometry. :

The staring material which takes part in

chemical reaction is called as reactant, the

substance formed after the chemical reaction

is called product from the balanced chemical

reaction.

Stoichiometry is a process of making

calculation based on formulae and balanced

chemical equations. In the balance chemical

reaction.

2N2 (g) + 3H2(g) 2NH3(g)

These coefficients of reactants and products

in the balanced chemical reaction are called

as stoichiometric coefficients.

PROBLEM :

Write the balanced chemical equation for

reaction between iron and chlorine to form

ferric chloride.

Solution :

Step – I

Iron(s) + chlorine (g) ferric chloride (s)

Step – II

Fe(s) + Cl2(g) FeCl3 (s)

Step – III

2Fe(s) + 3Cl2(g) 2FeCl3(s)

This is the balanced chemical reaction.

Write the balanced chemical reaction between

aqueous solution of ferric chloride and metallic

zinc.

Solution :

Step – I

Ferric chloride + zinc zinc chloride +iron

Step – II

FeCl3(aq) + Zn(s) ZnCl2 (aq) + Fe(s)

Step – III

2FeCl3(aq) + 3Zn(s) 3ZnCl2 (aq) + 2Fe(s)

This is the balanced chemical reaction.

Mass relationship. : A balanced chemical

reaction may be used to establish the weight

relationships of reactants and products. This is

based on law of conservation of mass which

states that, total mass of reactants is always equal

to total mass of the products.

Limiting and excess : It is the reactant that

reacts cmpeletely but limits further progress of

the reaction. The excess reactant is the reactant

which is taken in excess than the limiting

reactant.

=*=*=*=*=*=*=*=*=*=

Names and symbols of some elements

Element Symbol Element Symbol Element Symbol Element Symbol

Aluminium Al Chlorine Cl Eiesteinium Es Holmium Ho

Argon Ar Calcium Ca Fluorine F Iodine I

Silver Ag Chromium Cr Francium Fr Irridium Ir

Gold Au Cobalt Co Iron Fe Krypton Kr

Actinium Ac Copper Cu Galium Ga Lithium Li

Americium Am Cadmium Cd Germanium Ge Lanthanum La

Beryllium Be Caesium Cs Gadolinium Gd Lutetium Lu

Boron B Cerium Ce Hydrogen H Laurencium Lr

Barium Ba Curium Cm Helium He Magnesium Mg

Bismuth Bi Calefornium Cf Halfnium Hf Maganese Mn

Carbon C Erbium Er Mercury Hg Molybdenum Mo

Names and symbols of some elements

Element Symbol Element Symbol Element Symbol

Mendelivium Md Lead Pb Sulphur S

Nitrogen N Palladium Pd Scandium Sc

Neon Ne Platinum Pt Selenium Se

Nickel Ni Promethium Pm Strontium Sr

Neobium Nb Protoactinium Pa Sodium Na

Neodymium Nd Plutonium Pu Technicium Tc

Neptunium Np Radium Ra Uranium U

Oxygen O Rubidium Rb Tungston W

Osmium Os Ruthenium Rn Vanadium V

Potassium K Rhodium Rh Xenon Xe

Phosphorous P Rhenium Ru Ytterbium Yb

Zirconium Zr

Introduction of organic chemistry : It is a branch of chemistry which deals with study of co-valently

bonded carbon compounds.

But there are some exceptions Carbon monoxide CO, Carbon dioxide CO2, Carbon disulphide CS2,

Cyanides KCN, Carbides CaC2 etc. These compounds are studies in inorganic chemistry, because of their

properties.

Bonds : It is attractive force which binds two or more atoms together. These are mainly three types-

1. Ionic or electrovalent bond : It is a attractive force created by transfer of electron from one atom to

another atom or attractive force present between cation and anion.

2. Covalent bond : It is attractive force created by equal sharing of electrons.

3. Coordinate or dative bond : It is a attractive force created by sharing of lone pair of electrons.

Valency : " It is combining capacity of an element in its molecule. " or ' Valency is the number of

hydrogen atoms combining with one atom of an element to form its compound and it depends on the valence

electrons."

Lone pair of electrons : It is the number of nonbounded pair of electrons (lone pair of electrons) in the

outer most orbit. e.g. nitrogen contain one lone pair. Oxygen contain two lone pair.

Tetravalency of carbon atom : Tetra valancy of carbon atom is explained on the basis of electronic

configuration.

ground state electronic configuration

excited state electronic configuration.

Carbon contain four unpaired electrons in the outermost orbit, hence it is tetravalent.

Modern concept of covalent bond : Covalent bonds are formed by overlapping of atomic orbitals i.e, s,p.

These are two tpyes of covalent bonds -

1. Sigma ( ) covalent bonds : This type of bonds are formed by end to end / axel overlapping of atomic

orbitals. The overlapping is possible between s-s, s-p and p-p atomic orbitals e.g. H2 molecule - s-s

overlapping, HCl molecule -s-p overlapping, Cl2 molecule - p-p overlapping.

2. Pi( ) covalent bonds : This type of bonds are formed by lateral or parallel or sidewise overlapping of

atomic orbitals. The overlapping is possible between p-p atomic orbital.

Formation of single, double and triple bonds : All organic compounds are covalent and in all organic

molecule carbon is tetra valent. It has tendancy to form single, double and triple covalent bond with itself

or other elements.

1. Single covalent bond : It is formed by sharing of one electron from each atoms. It is always covalent

bond.

e.g. C-C, C-H, C-O, C-X etc.

2. Double covalent bond : It is formed by sharing of two electrons from each atoms. In which one is -

bond and another is -bond.

e.g. >C = C<, >C=O etc.

3. Triple covalent bond : It is formed by sharing of three electrons from each atoms. In which one is -

bond and two bonds are .

e.g. - C C-, -C N etc.

Hybridisation : Mixing of dissimilar oribits of same energies to form a new orbitals is knwon as

hybridisation. These are,

1. sp3-hybridisation : This type of hybridisation involves mixing of one's and three 'p' orbitals to form a

four same sp3 - hybrid orbitals. It has 25% s character and 75% p character.

This type of hybridisation takes place in the formation of saturated compounds.

e.g. CH4, C2C6, CCl4, CHCl3, SiCl4, NH3, H2O, CH3X, ROH etc.

2. sp2-hybridisation : This type of hybridisation involves mixing of one 's' and two 'p' orbitals to form a

three same sp2- hybrid orbitals. it has 33.3%s character and 66.6% p character.

This type of hybridisation takes place in the formation of compounds.

i.e. aldehydes, ketones, acids, esters, alkenes, AlCl3, SO2, SO3, ,

, , > C=S etc.

Chemistry

Basic Concept in Organic Chemistry

3. sp-hybridisation : This type of hybridisation involves mixing of one 's' and one 'p' orbitals to form a two

same sp-hybrid orbitals. It has 50%s character and 50% p character.

This type of hybridisation takes place in the formation of compounds.

This type of hybridisation takes place in the formation of compounds i.e, alkynes (-C ), nitriles

(-C N), BeX2 , BeH2, CO2, N2 etc.

Note : In short, always mind that single bond, double bond and triple bond and triple bond are formed by

Hybridisation of central atom (h) = No. of -bonds+ No. of lone pair of electrons +

No. of co-ordinate bonds.

If h = 4 central atom is sp3 -hybridised.

h = 3 central atom is sp2 -hybridised.

h = 4 central atom is sp -hybridised.

Structural representation of organic compounds :

Structural formula : It shows the actual attachment of groups or atoms from one another in a

molecule or arrangement of groups or atoms in space.

Strucutral formula is represented by complete, condenced and bond line formula.

1. Complete structural formula or Lewis structure : It representing the two covalently bonded

electrons by dash. The das represent the single, double and triple bond i.e., C-C, C C C, C N etc.

The lone pair of electrons on hetero atom may or may not be shown R-C N or R-C

2. Condensed formula : The structural formula can be condenced by omitting some or all covalent bonds.

e.g. CH4, CH3CH3 or CH3 CH3

CH3 CH2 CH2 CH2 CH2 OH or CH3 (CH2)4 OH

3. Bond line formula : It is the another way to represents the structure of organic compounds.

In this structure carbon and hydrogen are not shown and the line representing C C bonds are drawn in

zig-zig fashion. The terminal denote CH3 group unless indicate the functional group.

e.g. CH3 CH2 CH2 CH2 CH2 CH3 or

CH3 CH2 CH2 CH2 CH2 CH3 COOH or COOH

CH3 CH=CH CH2 CH2 CH3 or

Polar and nonpolar bonds : The nature of the covalent bond can be predicted on the basis of

difference of electronegativities between two bonded atoms.

Electronegativity of atom is a power of an atom to attract shared pair of electrons towards itself in a

molecule.

The electronegativity of some common atom is,

C - 2.5, H -2.1, 0 -3.5, N - 3 or 3.1, F - 4, Cl - 2.9 or 3, Br - 2.8, I - 2.5 or 2.6, Si - 1.8 etc.

1. Palar covalent bond : The bond in which the electronigativity difference between two bonded atom is

more than 0.5.

The molecule is said to be polar if it contains one or more polar bonds and there are separate centre of

positive and negative charge in the molecule.

2. Non-polar covalent bond : The bond in which the electronigativity difference between two bonded

atom is less than 0.5.

The polarity and non polarity of bonds can leads to polarity and non-polarity of the molecules and can

be affected melting point, boiling point, solubility etc. of the molecule.

Note : A symmetrical molecule is non-polar even though it contains polar bond because they have some

positive and negative centre. e.g. CO2, CCl4, CHCl3, CS2, BF3, PCl5 etc. are non polar.

Oxidation state or oxidation number : It is a total charge carried out by atom in its molecule. The

charge may be perfect ionic charge or particle charge, which may be associated with the atom due to

particle shifting of electron as in covalent compounds. Oxidation state may be positive, negative, zero

and even fractional. One atom may possess different oxidation number in different compounds.

Oxidation number of an atom may be calculate by following rules-

1. Oxidation number of an element in the uncombined state is zero. e.g. Na, Cu, Ag, Si, Al, Mg etc.

2. Oxidation number of an atom in a molecule of the same elements is zero. e.g. X2, O2, P4, S8 etc.

3. The algebric sum of oxidation state of various atom in molecule is zero because the molecule as a

whole is electrically neutral.

e.g. KMnO4 1 + X + 4 (-2) X = +7 The oxidation state Mn is +7

4. The algebric sum of the oxidation state of various atom present in an ion is equal to ionic charge.

e.g.

X + 3 (-2) = -2 X - 6 = -2 X = +4 The oxidation state of S is +4

Nomenclture : General IUPAC rules : '

1. Word root : It indicates the number of carbon atomes present in parent chain.

Carbon chain Word rood

C1 meth

C2 eth (a)

C3 prop (a)

C4 but (a)

C5 pent (a)

C6 hex (a)

C7 hept (a)

C8 oct (a)

C9 non (a)

C10 dec (a)

C11 undec (a)

C12 doded (a)

2. Primary suffix : It indicates the saturation and unsaturation in carbon chain.

Nature of corbon chain Primary suffix

saturated carbon chain

unsaturated carbon chain

one C = C

two C = C

three C = C

one C C

two C C

three C C

ane

ene

diene

triene

yne

diyne

triyne

3. Secondary suffix : It indicates the functional group of organic compound. It is added to the

primary suffix by dropping its terminal 'e'

Note : The terminal 'e' is dropped when secondary suffix beginning with vowel a, e, i, o, u or y but

retained if secondary suffix is not started with vowel.

Class of organic compound Secondary suffix IUPAC name

Alcohol ol Alkanol

Aldehyde al Alkanal

Ketone one Alkanone

Casboxylic acid oic acid Alkanoic acid

Sulphonic acid (So3H) sulphonic acid ----

Amine amine Alkanamine

Ester oate Alkyl alkanoate

Cyanide nitrile Alkane nitrile

Isocyanide isonitrile Alkane isonitrile

Thio alcohol (SH) thiol Alkane thiol

Acid hadile oyl halide Alkanamide

Amide amide Alkanamide

Acid unhydride oic unhydride Alkanoic unhydride.

4. Primary Prefix : It is used to distinguish between acyclic and cyclic compounds. If cyclic

compound is present word 'cyclo' is used before the word root.

If the prefix 'cyclo' is not used it indicate that the compound is acyclic or open chain.

5. Secondary Prefix : It indicates the substituent’s or alkyl groups. These are put before the word

root while naming the compounds.

Symbol / Substituents group Secondary suffix

OH

OR

SH

SR

NH2

NHR

methyl or me

ethyl or et

n-propyl or n-pr

holo

hydroxy

alkoxy

mercapto

alkyl thio

amino

alkyl amion

Symbol / Substituents group Secondary prefix

- NR2

- CN

R-CH = CH -

- CHO

R - C

- COOH

- COOR- COX

- CONH2

- NO2

- NO

dialkyl amino

mino

cyano

alkenyl

formyl or alkanoyl

oxo or keto

alkynyl

carboxy

alkoxy carbonyl or crab alkoxy

halo carbamoyl or carboxamido

nitro

nitroso

The complete IUPAC name of organic compound is -

Secondary prefix + primary prefix + word root + primary suffix + secondary suffix

CH3 C2H5

| |

Ex : CH3 C C CH3

| |

CH3 OH

Secondary prefix + word root + primary suffix + secondary suffix

2, 2, 3, trimethyl + pent + ane (e) + 3-ol

2, 2, 3, trimethyl pentan - 3 - ol or 3 - pentanol

The IUPAC rules 1. Longest chain rule :

a) Longest chain of carbon atoms (may be saturated or unsaturated) is selected as parent hydrocarbon.

If any functional group is present select longest chain containing functional group.

b) If more than one set of longest chain are possible then select longest chain should have maximum

number of side chain or minimum number of branched side chain.

2. Lowest number rule :

a) Lowest number is given to the first side chain (alkyl group) or a substituents (Cl, Br, NO2, NH2,

OH, OCH3 etc.)

CH3 - CH2 - CH (CH3) - CH3 2-methyl butane

If side chain or alkyl group and substituents are at same position the lowest number is given to

substituents.

CH3 - CH (CH3) - CH (OH) - CH3 3-methyl 2-butanol

If functional group is equidistance from both the side, thus next lowest number is given to the alkyl

group.

CH3 - CH (CH3) - CH2 - CH (OH) - CH2 - CH2 - CH3 2-methyl 4- heptanol

b) If two different alkyl groups are equidistance from both the side, lowest number is given to that alkyl

group, which comes first in alphabetical order (methyl comes after ethyl) along with their

appropriate number.

(It may be noted that di, tri, tetra etc. are not considered for alphabetical order)

CH3 - CH2 - CH (C2H5) - CH (CH3) - CH2 - CH3 3-ethyl 4-methyl hexane

c) If more than two alkyl groups (side chain) and substituents (functional group) are present the sum of

their number should be lowest at first preference, irrespective of the number of the side chain or

substituents. 1 2 3 4 5 6 7

CH3-CH2-CH(CH3)-C(Cl)(CH3)-CH2-CH2-CH3

Set of locant - 3, 4, 4 sum 3 + 4 + 4 = 11

4-chloro 3, 4 - dimethyl heptane (right)

7 6 5 4 3 2 1

CH3-CH2-CH(CH3)-C(Cl)(CH3)-CH2-CH2-CH3

Set of locant - 4, 4, 5 sum 4 + 4 + 5 = 13

4-chloro 4, 5 - dimethyl heptane (wrong)

d) If the substituent on the parent chain is branched (complex), it is also numbered from carbon atoms

attached to parent chain as one. The name of such substituents is written in bracket, in order to avoid

any confusion with numbering the parent chain.

Branched alkyl groups IUPAC names Comman names

(CH3)2 CH - 2-propyl or 1-methyl ethyl Iso-propyl

CH3-CH-C2H5 2-butyl or 1-methyl propyl Sec. butyl

(CH3)2CHCH2 - 2-methyl 1-propyl Iso-butyl

(CH3)3C - 2-methyl 2-propyl or 1, 1-dimethyl ethyl

Example : 2 1 4 5 6 7 8 CH3-CH-CH-CH2-CH2-CH2-CH3 2,3-dimethyl 4(1-methyl ethyl) octane

CH33CH -CH3

2CH-CH3

1CH3

IUPAC nomenclature of polyfunctional compounds

In case of polyfunctional compounds (compounds containing more than one functional group) one of the

functional group treated as principal functional group and is regarded as secondary suffix and other functional

group regarded as substituents and are indicated by prefixes.

The IUPAC system laid down the priority and functional groups for determining the class of a

polyfunctional compounds.

The functional group which occurs higher up in priority is the principal functional group and is specified

the class.

Class Functional groups Class Functional groups

1) sulphonic acids

2) carboxylic acids

3) acid anhydride

4) esters (alkoxy carbonyl)

5) acid halides (Halo formyl)

6) amides (Carbamoyl)

7) nitriles / isocyanides

8) aldehydes (Formyl)

9) Ketones (Oxo / Keto)

-SO3H

-COOH

(RCO)2O

-COOR

-COX

-CONN2

-CN / -NC

-CHO

CO

10) alcohols / Phenols

11) amines

12) alkenes

13) alkynes

14) ethers (Epoxy)

15) Halo

16) Nitro

17) Alkoxy

18) Alkyl

-OH

-NH2

C=C

- C C -

-O-

-X

-NO2

-OR

-R

Note : All remaining groups i.e. halo, nitro, alkoxy etc. are always treated as substituents.

i) Principal functional group is COOH because it comes higher up in priority.

ii) Work root : OCT (8 Carbon atoms)

iii) Primary suffix : ene (Chain containing C=C bond)

iv) Secondary suffix : oic acid ( COOH group comes higher up in priority).

v) Prefixes : Nitro, hydroxy, oxo, methoxy, bromo.

Complete IUPAC name of compound is,

6 bromo, 4 hydroxy, 7 methoxy, 4 nitro, 5 oxo, oct-2-en, 1-oic acid.

Isomerism :

Isomerism : Compounds have the same molecular formula but differ from each other in physical and

chemical properties, called isomers and phenomenon is known as isomerism. The difference in properties

of isomers is due to the difference in the relative arrangement of various atoms or groups present in their

molecules.

There are two types of isomerism,

1) Structural isomerism

2) Stereoisomerism.

1. Structural isomerism : Compounds have same molecular formula, but different in structural

formula.

Structural isomerism is of five types,

i) Chain or nuclear or skeletal isomerism : It is shown by the compounds which differs in the

arrangement of carbon atoms.

e.g. CH3CH2CH2CH2X n-butyl halide

(CH3)2 CHCH2X isobutyl halide

ii) Position isomerism : It is shown by the compounds having same carbon chain, but different in

the position occupied by substituent group or atom.

e, g. CH3CH2CH2Cl 1 - chloropropane

CH3CHClCH3 2 - chloropropane

iii) Functional isomerism : It is shown by the compounds having smae molecular formula, but

different functional group.

Alcohols and ethers, acids and esters, aldehyde and ketones, glucose and fructose, 10, 2

0, 3

0

amines, cyanides and isocyanides, nitroalkanes and alkyl nitrite, are the functional isomers.

e.g. 1. Molecular formula C2H6O has two isomers.

CH3CH2OH ethyl alcohol.

CH3OCH

3 dimethl ether.

2. Molecular formula C2H4O2 has two isomers.

CH3COOH acetic acid

HCOOCH3 methyl formate

3. Molecular formula C3H6O has two isomers.

CH3CH2CHO Propanal

CH3COCH3 dimethyl ketone.

iv) Metamerism : Metamerism is present in same class of compounds. It is a isomerism due to the

unequal distribution of carbon atoms on either side of functional group. Esters, Ethers, 20

and 30 amines, ketones shown metamerism

e.g. 1. Diethyl ether and methol n = propyl ethers are matameres.

CH3CH2OCH2CH3 diethyl ether.

CH3OCH2CH2CH3 methyl n = propyl ether.

Note : If same polyvalent functional group is there in two or more organic compounds, then never

write chain and position isomerism, it will be metamerism.

Ex. :- 2-pentanone and 3-pentanone are metamers and not position isomers.

v) Tautomerism : It is a special case of functional isomerism. When two structural isomers are

mutually interconvertable by migration of proton and exist in dynamic equilibrium, knwon as

tautomers and phenomenon is known as tautomerism.

e.g. Aldehydes and ketons shows tautomerism..

2. Stereoisomerism (Space isomerism ) : The isomers having same molecular and structural

formula, but different in configuration (The term configuration refers to three dimensional

arrangement of atoms or group in space )

Stereoisoers are of two types,

i) Geometrical isomerism (cis-trans isomerism) : The isomer having same molecular formula and

structural formula but different in spatial arragment of the groups or atoms around the double bond. It is

shown by the alkenes and their derivatives. Cis trans isomers have different physical and chemical

properties.

When similar groups at the same side of the double bond is known as cis isomer.

When similar groups are at the different side of the double bond is known as trans isomer.

Remember that geometrical isomer is possible when each of the doubly bonded carbon atom have

two different groups.

Thus compound of the following type does not show geometrical isomerism.

e.g. aaC+Cxy, aaC=Cxx, axC=Caa.

e.g. : 2-butene shows cis and trans isomerism. Trans form is stable than cis form, this is because the

bulky groups are on the opposite side of the double bond. The steric repulsion of the bulky groups

present at same side makes cis isomer less stable.

ii) Optical isomerism : It is a molecular phenomenon arises from different arrangement of groups

or atoms in three dimensional space resulting in two somers which have non- super imposable mirror

image of each other. These compounds have same physical and chemical properties except action on

plane polarized light.

It may be noted that molecules having only one chiral centre are always optically active.

e.g. Lactic acid, 2-halobutane, 2-butanol, glucose, fructose, -amino acids (except glycine)are optical

active.

Types of carbon atoms :

1. Primary carbon atoms (10) : The carbon atom which is attached to another only one carbon atom or

solitary carbon atom.

2. Secondary carbon atoms (20) : The carbon atom which is attached to another two carbon atom.

3. Tertiary carbon atoms (30) : The carbon atom which is attached to another three carbon atom.

4. Quaternary carbon atoms (40) : The carbon atom which is attached to another four carbon atom.

Types of hydrogen atoms

1. Primary hydrogen atoms (10) : The hydrogen atoms which are attached to primary carbon atoms.

2. Second hydrogen atoms (20) : The hydrogen atoms which are attached to secondary carbon atoms.

3. Tertiary hydrogen atom (30) : The hydrogen atoms which are attached to tertiary carbon atoms.

Ease of abstraction of hydrogen atom during substitution reaction is,

30 H> 2

0 H> 1

0 H

10

20

401

0 1

0 2

0 1

0 1

0

Alkyl groups (R) : These are formed by removing one hydrogen atom from corresponding alkanes.

Functional groups :

The groups or atoms which decide the properties of organic compounds are known as functional groups.

Bond fission : Organic compounds are made up of covalent bonds. Organic reaction involve breaking of

covalent bond. When the two atoms joined by the covalent bond are separated, the process is termed as

fission or cleavage or breaking of bond.

It is of two types.

1. Homolytic bond fission : Homolysis (Homo= Similar, Lysis = Breaking)

The symmetrical breaking of a covalent bond in the presence of U.V. light or diffisued sunlight or non polar

solvent or peroxide or at high temperature to form free radicals is called as hemolytic fission or homolysis.

A – B A●+ B●

e.g. H – H H●+ H●

Free radicals.

2. Heterolytic bond fission : Heterolysis (Hetero = Dissimilar, Lysis = Breaking ) :

The unsymmetrical breaking of a covalent bond in the presence of polar solvent or reducing agent or

oxidizing agent or acid or base to form cation and anion is called as heterolytic fission or heterolysis.

Electrical displacement or mobility of electrons :

1. Inductive effect (I-effect)/Mobility of electrons in single covalent bond : “The permanent

polarization of transmission of electron pair of single covalent bond due to difference in

electronegativities between two bonded atoms is called inductive effect.”

It is of two types :

a) + I effect : It is the effect due to electron donating or repelling groups of atoms than hydrogen.

e.g. ( )3 C > ( )2 CH > CH3CH2 > CH3 > H

The other electron donating ions are COO , S

2-

b) I effect : It is the effect due to electron attracting or accepting groups or atoms than hydrogen.

e.g. NO2 > CN > COOH SO3H > F>Cl>Br > I > OR >OH>NH2>H

2. Electromerit effect (E – effect) / Mobility of electrons in multiple bond : “ The complete temporary

transfer of pi – bonded electron pair from one atom to another atom of a multiple bond system inpresence of

attacking suitable reagent is called electromeric effect. “

It is of two types :

a) Positive electromeric effect : (+E effect) : When transfer of electron pair takes place towards the

suitable attacking reagent (electrophilic reagent) is called positive electromerit effect.

It takes place in > C = C <, – C C – bonds.

b) Negative electromeric effect : (-E effect) : When transfer of electron pair take place away from the

suitable attacking reagent. (nucleophilic reagent) is called negative inductive effect.

It takes place in > C = O, – C N bonds.

3. Resonance of Mesomeric effect : It is the permanent effect in which electrons are transmitted from

one part of the conjugated system to other part creating positive and negative centre due to resonance is

known as resonance or mesomeric effect.

4. Steric effect of Steric strain or Steric hindrance or Vander Waals strain : It is a repulsion between two

or more groups or atoms in a molecule is known as steric effect.

The two atoms or groups in aorganic molecule at a distance less than or equal to Vander Waals redius (It is

a half of distance between the nuclei of two adjacent atoms in a solid state). Repell each other due to spatial

crowding. Molecule with steric effect are relatively less stable as compared to hose having no steric strain.

Note : Steric effect influence reactivity and structure of organic compounds e.g. Basicity of anines depends

up on steric effect.

e.g.

Reagents : “Electron deficient or electron rich or neutral species which attacks on substrate in a chemical

reaction is called reagent.”

1. Free radicals : These are neutral species having odd electrons, ex. Cl●

2. Electrophilic reagents : Electrophiles (Electro = Electrons, Philic = Loving, Attracting) : Electron

(Negative centre) Loving : These are positively charged ions, or electron deficient neutral molecule.

They have tendency to accept electrons and acts as Lewis acids.

They attacks on negative centre or electron rich centre or region of high electron density.

These are electron pair acceptor for sharing to form co-ordinate bond.

e.g. Ions : H+, R

+, NO

+, NO2

+, Br

+, Cl

+, I

+, RCO

+ ,H3O

+, NH4

+, HSO3

+, C6H5N2

+ etc.

Neutral molecules : AlX3, BX3, BeX2, ZnCl2, PCl5, HCl, HBr, HI, H2SO4, HNO3, : CR2, :CCl2,

CO2, RCOCl, (RCO)2O, SO3 RN2+, ICI, NR(nitrene)NOCl2, X2, SiF4 etc.

3. Nucleophiles (Nucleo – Nucleus, philic - = Loving, Attracting) : Nucleus (positive centre) Loving :

These are negative charged ions, electron rich neutral molecule. They have tendency to donate electrons

and acts as Lewis bases.

They attack on positive centre or electron deficient centre or region of low electron density.

These are electron pair donor for sharing to form co-ordinate bond.

e.g. Ions :

Neutral molecules : RLi, ,

Reactive Intermediates :

Most of the organic reaction occurs through a intermediate, there are generally short lived and highly

reactive.

The shoroto lived highly reactive chemical species through which all most rections occur are called reactive

intermediates. These are

a) Carbonium ion (carbocation) : These are trivalent positively charged carbon species

containing six electrons in outer most orbit.

b) Carbon : These are trivalent negatively charged carbon species containing eigthit

electrons in outer most orbit.

c) Carbon free radicals : These are trivalent charg;ess or neutral species contaioning

odd lectrons. These are more reactive than ionic species.

d) Carbene : These are divalent chargless or neutral carbon species containing six

electrons in outer most orbit.

These are formed by photolysis or thermolysis or in the presence of acid or base.

e.g. CH2 = = N : CH2 + N2

Organic reactions :

In chemical reaction, reagents attacks on substrate to ooyield the product of the reaction.

Substrate + reagent products (main product and side product)

In chemical reaction bonds of Substrate are broken to form a intermediate fragments. These fragments

are very reactive, reacts with other species to form a new bonds to give a products.

Type of reactions

These are classified into four main types,

1) Addition reactions

2) Substitution reactions

3) Elimination reactions

4) Rearragement reactions

1. Addition reactions : The reaction in which reagents are added across the multiple bond i.e.

C=C, C C, C=O, C N, C=S, to form a single product.

In this reaction at least one bond is broken and two new a bonds are formed

e.g. CH2 = CH2 + HBr CH3CH2Br

>C=O + HCN > C(CN)OH

These reactions are three types,

i) Electrophilic addition reactions(EAR) : The addition reaction in which the initial attack

of electrophile, such reactions are given by compounds containing >C=C<, C C bonds

(unsaturated compounds)

ii) Nucleophilic additon react6ions : The addition reactions in which the initial attacko of

nucleophile such reactions are given by compounds containing bonds.

iii) Free radical; addition reactions(FAR)(Non ionic addition reactions) :

The addition reac tions in which the attacko of free radical.

Free radical reactions tkes place in non-polar solvent or high temperature or in presence of

U.V. light or diffused sunlight or free radical producing substances like and organic

peroxide. (R2O2)

Addition of HBr in propylene(say asymmetrical alkene) in presence o peroxide follows the free

radical mechanism

CH3CH=CH2 + HBr CH3CH2CH2Br

2. Substitution reactions : The reactions in which groups or atoms are replaced by another groups

or atoms.

These reactions are three types,

i) Electrophilic susbstitutuin reactions (ESR) : The susbstitution reactions in which the

initial attacok of electophile.

Halogenation, Nitration, sulphonation of alkanes and aromatic compounds (benzene,

phenols) are the few examples of such reactions.

CH4 + Br2 CH3Br + HBr

ii) Neclephilic substitution reactions (NSR) : The substitution reactions in which the

initial attack of nucleophile.

Hydrolysis of alkyl halide, esters, amide formation, unhydride foromation, esterification,

alkylation of amines, a acylation of amines are few examples of such reactions

RX + KOH ROH + KOH

iii) Free radical substitution reactions (Non-inonic susbtitution reactions) :

The reactions which involves the attack of free radical.

Chlorination of alkane impresence of ultra violet light is a typical example of free

radical substitution reaction.

CH4 + Cl2 CH3Cl + HCl

3. Elimination reactions : The reaction in which smaller molecule is removed from a-a carbon atoms

or carbon atoms and produces multiple bonded compounds.

i.e. > C = C<, > C = O

This reaction is reverse of addition reaction. In this reaction atleast two bonds are broken and one

bond is formed.

i) elimination reactions : The reaction in which smaller molecule is removed from carbon

atoms and produces multiple bonded compounds.

e.g. dehydrogenation or catalytic oxidation of alcohols.

CH3CH2OH+

> CH3CHo + H2

ii) elimination reactions : The reaction in which smaller molecule is removed from carbon

atoms and produces unsaturated compounds.

Dehydrohalogenation of alkyl halides and dehydration of alcohols ate the examples of elimination

reactions. However, compound having unequal number of hydrogen atoms elimination takes place by

Saytzeff rule.

CH3CH2Br + KOH CH2=CH2 + H2O + KBr

CH3CH2OH CH2=CH2 + H2O

4. Rearrangement reactions : These are the reactions which involves the inigration of atom or group

to another position in the molecule containing double bond to form a product with new structure.

CH2=CHOH CH3CHO

vinyl alcohol acetaldehyde

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*