INTRODUCTION TO ORGANIC
CHEMISTRY
P Nagaraja
Assistant Professor in Chemistry
RGUKT- RK Valley, Vempalli, Kadapa
Introduction to Organic Chemistry
• Organic chemistry is defined as the study of carbon compounds containing usually
hydrogen and one or more additional elements like oxygen, nitrogen, halogens and
phosphorus etc.
• What makes carbon so special ?
• The high catenation property and tetravalent nature of carbon enable it to form
structurally diverse compounds.
• Catenation: The ability to form longer chains by linking to atoms of the same element is
known as catenation.
• Tetravalency of carbon: Carbon has four unpaired electrons in its excited state and
needs four more electrons to be stable. Thus, carbon always combines with other atoms
by mutual sharing of electrons and forms four covalent bonds.
• Carbon can form multiple bonds with itself and other elements
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General characteristics of organic compounds
• Organic compounds should contain C-H and C-C bonds
• They are covalent in nature
• Mostly they are gases and liquids
• They are volatile and inflammable in nature
• They have low melting and boiling points
• They are usually insoluble in water
• They have characteristic and sharp odor
• They exhibits isomerism
• The chemical reactions of organic compounds are slower
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Bonding in organic compounds
• Carbon in its excited state contain 4 unpaired electrons hence it can share its 4 electrons
and form four covalent bonds
• Therefore, organic compounds are essentially covalent in nature
• Hybridisation greatly affects the bond length, bond enthalpy and electronegativity of a
carbon compound.
• Three types of hybridisation − sp, sp2 and sp3, are seen in carbon atoms depending upon
how many atoms are linked to the carbon.
• An sp hybrid orbital has 50% s-character and 50% p-character;
• an sp2 hybrid orbital has 33.33% s-character and 66.66% p-character;
• an sp3 hybrid orbital has 25% s-character and 75% p-character.
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Bonding in organic compounds
Effect of Hybridisation on Single, Double and Triple Bond Lengths of Carbon
Since the sp hybrid orbital contains more s-character (50%), it is closer to its nucleus; therefore, it
forms shorter bonds. Because of the same reason sp2 hybrid orbital forms shorter bonds than sp3
hybrid orbitals.
The single, double & triple bond lengths in carbon follow the order: -C−C > -C=C- > -C≡CEffect of Hybridisation on Bond Strength (Bond Enthalpy)
The strength of the bond increases as the length of the bond decreases. As a result, bond enthalpy
decreases from sp to sp3 i.e., : sp > sp2 > sp3.
In terms of C−C bond, bond enthalpy follows the order : C≡C (strongest) > C=C > C-C
Effect of hybridisation on electronegativity
The greater the s-character of the hybrid orbitals, the greater is the electronegativity because an sorbital holds electrons more tightly to the nucleus.
In terms of Electronegativity: sp > sp2 > sp3.
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Structural Representations of Organic Compounds
The structures of organic compounds are represented in several ways.
Complete structural formulae
Complete structural formulas show all the atoms in a molecule, the types of bonds connecting them,
and how they are connected with each other. For example, consider ethane, ethanol and acetone are
given below
Condensed structural formulae
Complete structural formulae can be further abbreviated by omitting some or all the dashes
representing covalent bonds. For example, the formulae of butane are given below
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Structural Representations of Organic Compounds
Bond-line structural representation
In Bond-line structural representation, carbon and hydrogen atoms are not shown and the lines
representing carbon-carbon bonds are drawn in a zig-zag fashion. Only heteroatoms are written in
bond line representation.
Cyclic compounds are usually represented by bond line formulae
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Classifications of Organic Compounds
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Classifications of Organic Compounds
Organic compounds are broadly divided into two categories
1.Acyclic compounds (open chained)
2.Cyclic compounds (closed chained)
Acyclic compounds
 Acyclic compounds contain open chains of carbon atoms in their molecules.
 The carbon chains may be either straight chains or branched chains.
 Open chain compounds are also called aliphatic compounds
CH3-CH2-CH2-CH3 → n-butane
CH3-CH=CH-CH3 → But-2-ene
Branched alkane
Isopentane
Cyclic Compounds
 Cyclic compounds contain one or more closed chains or rings of atoms in their molecules.
 Based on the constitution of the rings, cyclic compounds are further divided into
1.Homocyclic or carbocyclic compounds.
2.Heterocyclic compounds.
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Classifications of Organic Compounds
Homocyclic Compounds
 Homocyclic compounds contain rings which are made up of only carbon atoms. They are also
known as carbocyclic compounds.
 Homocyclic compounds are further divided into following categories.
1.Alicyclic homocyclic compounds.
2.Aromatic homocyclic compounds
Alicyclic Homocyclic Compounds
Homocyclic compounds which resemble
acyclic compounds in most of their properties
are called alicyclic homocyclic compounds.
Aromatic Homocyclic Compounds
Organic compounds containing one or more
benzene rings and their functionalized
derivatives are called aromatic compounds.
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Classifications of Organic Compounds
Heterocyclic Compounds
Cyclic compounds containing one or more heteroatoms in their rings are called heterocyclic
compounds.
Heterocyclic compounds are also divided into two categories
1. Alicyclic heterocyclic compounds.
2. Aromatic heterocyclic compounds.
Alicyclic Heterocyclic Compounds
Alicyclic compounds, containing one or
more heteroatoms in their rings are called
alicyclic heterocyclic compounds.
Aromatic Heterocyclic Compounds
Aromatic cyclic compounds containing one
or more heteroatoms in their molecules are
called aromatic heterocyclic compounds.
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Functional Groups
 Hydrocarbons are the parent of all organic compounds. Hydrocarbons consist of only carbon and
hydrogen atoms.
 All other organic compounds are derived from hydrocarbons by replacing one or more of their
hydrogen atoms. The groups that replace hydrogen from hydrocarbons are known as Functional
Groups.
 Functional groups determine the chemical properties of organic compounds. For example CH3−OH
and CH3CH2CH2−OH have similar chemical properties due to the presence of the same functional
group (−OH) despite being attached to the chains containing different number of carbon atoms.
Examples of functional groups: CH3−OH, CH3−CHO, CH3−COOH etc.
 A functional group may be defined as an atom or a group of atoms present in a molecule
which largely determines its chemical properties.
All molecules other than hydrocarbons consist of two parts:
Carbon-hydrogen framework & Functional Groups
 Carbon-hydrogen frameworks (usually denoted by R) mainly affect the physical properties of the
compound such as melting point, boiling point, density, solubility, refractive index etc.
 Functional groups determines the chemical properties.
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Functional Groups
Based on type of bonds present in the molecule, functional groups may be classified as
Compounds contains C-H
Hydrocarbons
Compounds contains C-Z
Z= X, OH, OR, -NH2
Compounds contains C=O
Carbonyl compounds
Alkanes
Alkyl halides
Aldehydes & Ketones
Alkenes
Alcohols
Carboxylic acids
Alkynes
Ethers
Esters
Aromatics
Amines
Acid chlorides
Amides
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Homologous Series
A homologous series is defined as a group or series of organic compounds all the members of which contain
same functional group and any two members of which differ by a -CH2 unit.
For example, consider the series of alkane molecules,
CH4 (methane) - C2H6 (Ethane) − C3H8 (Propane) - C4H10 (Butane) - C5H12 (Pentane) = CH2 unit.
 Clearly, each successive member of alkane family is differ by a CH2 unit.
 Such type of groups or series of organic compounds where adjacent members are differ by a CH2 unit, form
a homologous series and the members of the series are called homologues.
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Characteristics of homologous series
1.
2.
3.
4.
All the members of a series can be represented by the same molecular formula
Each member of the series differs from the members before or after it by a –CH2 group
All members of the series shows similar chemical properties
All members of the series shows a regular gradation in their physical properties as their molecular
mass increases
5. Generally, as molecular mass increases the melting point, boiling point, density and viscosity
increases
Melting point, Boiling point, Density, Viscosity increases
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Nomenclature of Organic compounds
The system of naming organic compounds is termed as nomenclature of organic compounds. The
following systems are used for naming organic compounds.
1. Common system or trivial system
2. IUPAC (International Union of Pure and Applied Chemistry) system
Trivial system is based on the origin or properties of the compound. Mostly they are Greek or Latin in
their origin. For example, CH3COOH is named as acetic acid as it is derived from vinegar (acetum),
CH4 is known as Marsh gas as it is found in marshes.
IUPAC system is a systematic and scientific method of naming the compounds based on its structure
In this system, the name of every organic molecule has three parts
1. The parent chain indicates the number of carbon atoms present in the longest continuous chain
2. The suffix indicates the nature of C-C bond and functional group present
3. The prefix indicates the nature, number and location of substituents present on parent chain
Prefix
Nature, number & location of substituents
+
Root word
+
Suffix
Nature of chain and functional group present
Number of carbon atoms in parent chain
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Nomenclature of Organic compounds
Word root: Word root denotes the
number of carbon atoms present in the
parent chain
Suffix
Suffix contain two parts
Primary suffix
It denotes the nature of carbon chain
Secondary suffix
It denotes the nature of functional group
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Nomenclature of Organic compounds
Prefix
Prefix contain two parts
Primary Prefix
It denotes the cyclic nature of compound
Prefix “cyclo” is added before word root
3 Carbon atoms
4 Carbon atoms
Prop+ane
But+ane
Secondary prefix
It denotes the nature, number and
location of substituents
Add “cyclo” before root word
Cyclopropane
Cyclobutane
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3 Carbon atoms
2-chloro+prop+ane
4 Carbon atoms
2-methyl+but+ane
2-chloropropane
2-methylbutane
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Naming Substituents




Carbon substituents are called alkyl groups.
An alkyl group is formed by removing 1 H from an alkane.
To name an alkyl group, change the “-ane” ending of the parent alkane to “-yl.”
Each alkyl group has a bond that can then be attached to something else
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Nomenclature of Saturated Hydrocarbons
•Step 1: Find the longest continuous carbon chain, and name it with an “-ane” ending.
Step 2: Number the atoms in the carbon chain such that substituent gets the lower
number.
CORRECT
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INCORRECT
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Nomenclature of Saturated Hydrocarbons
 If two or more same substituents are present on parent chain use prefixes di, tri,
tetra etc.
2,3-dimethylhexane
 If different substituents are present their names are written alphabetically
 If different substituents are located at different positions follow lowest sum rule
Parent chain: 8 C’s --- Word root –OctSuffix --- ane
Prefix’s: Two –CH3 at 3,4 positions, an ethyl at 4-position
4-ethyl-3,4-dimethyloctane
Prefix + word root + suffix (-ane)
*IUPAC name should be continuous, numbers are separated by comma, number-letter are separated by hyphen
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Nomenclature of unsaturated hydrocarbons
 Alkenes contain a carbon-carbon double bond. The primary suffix of alkenes is ene.
 Alkenes contain a carbon-carbon triple bond. The primary suffix of alkynes is yne.
Step 1: Select the longest continuous chain as parent chain (2013 recommendations). Earlier, the
chain containing the multiple bond used to be selected as the parent chain regardless of the
length of the chain. Locants (position of multiple bonds) are always placed before the suffix.
Step 2: Number the parent chain such that multiple bond gets the lower number
Step 3: If two or more multiple bonds are present use suffix –diene, triene etc.
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*IUPAC name should be continuous, numbers are separated by comma & number-letter are separated by hyphen
Nomenclature of unsaturated hydrocarbons
 If both double and triple bonds are present in the molecule they are named as Alkenynes.
If both double and triple bonds are present, the numbering of the parent chain start from the side
that give lowest possible number to the multiple bond
Hept-2-en-4-yne
However, if there is a choice in numbering, the double bond is always given preference over the
triple bond.
*IUPAC name should be continuous, numbers are separated by comma & number-letter are separated by hyphen
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Nomenclature of functional group containing molecules
•The following additional rules are applied while naming organic compounds containing one
functional group.
•1) Parent chain : The parent chain must contain the functional group irrespective of chain length
•2) Numbering of the parent chain should always be done from that end which is nearer to the
functional group.
•The suffix of the functional group is added to the end of the word root with its positional number.
3) When a carbon containing functional group such as -CHO, -COOH, -COCl is present at the
terminal, the carbon of the functional group is always assigned number 1.
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Nomenclature of polyfunctional compounds
•More than one occurrence of the same functional group
•When the same functional group appears more than once in the chain, suitable prefixes such as
di (for two), tri (for three), tetra (for four) etc., are added along with their positional numbers.
Polyfunctional Compounds: Organic compounds that contain two or more functional groups are
called polyfunctional compounds.
 In a polyfunctional compound, one of the functional groups is selected as the principal functional
group while all other functional groups are treated as substituents.
 Functional groups according to their priorities are listed in the priority table in decreasing order
i.e., Carboxylic acid with the highest priority is placed at the top while alkyne being the least in
priority is placed at the bottom.
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Nomenclature of polyfunctional compounds
 Remember, some groups like Cl, F, NO2 are always considered as substituents even when no other
functional group is present.
 If two groups of the same priority occupy identical positions from either end of the parent chain, the
lowest number must be assigned to the group whose prefix comes first in the alphabetical order.
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Nomenclature of Alicyclic Compounds
The following rules are generally used to name alicyclic compounds.
Cyclo : Prefix 'cyclo' is added to the word root of the alicyclic compounds.
Lowest sum rule : When two or more substituents are present in the alicyclic ring, the numbering is
done in such a way that the sum of the positional numbers of the substituents is the lowest.
Number alphabetically : If two or more substituents are present, then the numbering is done from
the substituent which comes first in the alphabetical order provided it satisfies the lowest sum rule.
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Nomenclature of Alicyclic Compounds
If more than two substituents are present in the alicyclic ring, numbering should follow lowest sum
rule and groups are listed alphabetically in name.
If functional group is present in the ring, numbering is given 1 and need not be mention in name
Priority : According to IUPAC 2013 recommendation, if both alicyclic ring and side chain are
present in the compound, the compound is named as a derivative of ring regardless of the length.
Prior to 2013 rules, priority was given to the part having greater number of carbon atoms, but not
anymore.
Butylcyclopropane (according to iupac 2013 rules)
Cyclopropylbutane (according to earlier rules)
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Isomerism in organic compounds
Two or more compounds having the same molecular formula but different chemical and physical
properties are called isomers and the phenomenon is known as isomerism.
There are two types of isomerism: 1. Structural isomerism & 2. Stereoisomerism.
Isomerism
Structural isomerism
Stereoisomerism
Chain isomerism
Positional isomerism
Functional group
isomerism
Geometrical
isomerism
Optical
isomerism
Metamerism
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Isomerism in organic compounds
 Structural isomerism
Compounds having the same molecular formula but different structures are known as structural
isomers. Structural isomerism is further divided into four subcategories.
1. Chain isomerism
Compounds having same molecular formula but different carbon skeletons are known as chain
isomers and the phenomenon is known as Chain isomerism.
For example, chain isomerism in butane and pentane are shown below
C4H10
C5H12
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Isomerism in organic compounds
2. Position isomerism
Compounds having same molecular formula but differ in the position of the multiple bond (double or
triple bond) or functional group are known as position isomers and the phenomenon is known as
position isomerism.
C3H7Cl
C4H8
1-chloropropane
2-chloropropane
3. Functional isomerism
Compounds having same molecular formula but different functional groups are called functional
isomers and the phenomenon is called functional isomerism.
C4H8O2
C2H6O
Butanoic acid
Methyl propanoate
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Isomerism in organic compounds
4. Metamerism
Compounds having same formula but different alkyl groups on either side of the functional group are
known as metamers and the phenomenon is known as metamerism.
Ethers, amines & ketones exhibit metamerism
CH3-CH2-NH-CH2-CH3
CH3-CH2-O-CH2-CH3
C4H10O
Diethyl ether
CH3-CH2-CH2-O-CH3
Methyl propyl ether
C4H11N
Diethyl amine
CH3-CH2-CH2-NH-CH3
Methyl propyl amine
5. Tautomerism
Compounds having same formula but differ in the position of H-atom are called tautomers and the
phenomenon is known as tautomerism. It arises due to 1,3-migration of a hydrogen atom within
the same molecule.
It is commonly exhibited by aldehydes and ketones & it is generally called keto-enol tautomerism
C3H6O
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Isomerism in organic compounds
Compounds having same formula, same connectivity but different spatial arrangement are known as
Stereoisomers and the phenomenon is known as stereoisomerism.
Different spatial arrangement
Of groups around double bond
Different spatial arrangement
Of groups around single bond
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Organic reactions and mechanism
Generally organic compounds are covalent in nature and hence all organic reactions involves
breaking and making of covalent bonds. Therefore, organic reactions consists of 3 types
1. Breaking of covalent bonds
2. Reaction intermediates
3. Types of organic reactions
A covalent bond breaks in two ways. Homolytic fission (homolysis) & Heterolytic fission (heterolysis)
1. Homolytic fission: If the bond breaks in such a fashion that each atom gets one electron of the
shared pair, it is called homolytic fission. The homolysis is shown by half headed arrow.
2. Heterolytic fission: When a covalent bond breaks in such a way that both the electrons of shared
pair shifts to one of the atom, then the cleavage is termed as heterolytic fission.
Homolysis produces freeradicals and heterolysis produces charged ions
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Reaction intermediates
 Cleavage of covalent bonds can produce reaction intermediates.
 Short lived & highly reactive species produced during the course of reaction are known as reaction
intermediates. They are Free radicals, Carbocations & Carbanions
Free radicals
Carbocations
Carbanions
Charge/species
Neutral
+ve charge
-ve charge
No. of valence e-s
7
6
8
Formed by
Homolysis
Heterolysis
Heterolysis
Solvent
Non-polar
Polar
Polar
Structure
Planar
Trigonal planar
Pyramidal
Hybridization of C
sp2
sp2
sp3
Types
Pri., sec. & tert.
Pri., sec. & tert.
Pri., sec. & tert.
Stability order
3o > 2o > 1o > Me-
3o > 2o > 1o > Me-
3o < 2o < 1o < Me-
Nature
Electrophilic
Electrophilic
Nucleophilic
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Reagents in organic chemistry
A reagent is a substance that brings a chemical change in the reactant(s)
In organic chemistry, reagents are broadly classified into two types
1. Electrophiles
2. Nucleophiles
Reagents
Electrophiles
Nucleophiles
 They are electron deficient species
 They can act as Lewis acids
 They reacts with electron rich centers
such as multiple bonds/lonepairs/-ve charges
 They may be charged or neutral
Examples: H+, Cl+ CH3+, CH3CO+, NO2+
Neutral: AlCl3, BF3, SO3, ZnCl2, SnCl2 etc.
 They are electron rich species
 They can act as Lewis bases
 They reacts with electron deficient centers
such as Vacant orbital/+ve charges
 They may be charged or neutral
Examples: H-, Cl- CH3-, CNNeutral: NH3, H2O, ROH etc.
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Types of organic reactions
Organic reactions are broadly classified into 4 classes
Addition
reactions
Substitution
reactions
Elimination
reactions
Rearrangement
reactions
 Reactions that involve the combination of two or molecules to form a new molecule are known as
addition reactions
 Additions reactions are characteristic reactions of unsaturated organic compounds
 In addition, an unsaturated compound converts to saturated compound
 Example: Alkenes and alkynes readily undergo addition reactions
 Addition reactions may be further classified into 3 types based on nature on attacking reagent
They are electrophilic, nucleophilic and free radical addition reactions
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Types of organic reactions
Organic reactions are broadly classified into 4 classes
Addition
reactions
Substitution
reactions
Elimination
reactions
Rearrangement
reactions
 Reactions that involve the replacement of atom or group by another atom or group are known as
substitution reactions
 Substitution reactions are characteristic reactions of saturated organic molecules
 Example: Alkyl halides, alcohols, carboxylic acids readily undergo substitution reactions
 Substitution reactions may be further classified into 3 types based on nature on attacking reagent
They are electrophilic, nucleophilic and free radical substitution reactions
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Types of organic reactions
Organic reactions are broadly classified into 4 classes
Addition
reactions
Substitution
reactions
Elimination
reactions
Rearrangement
reactions
 Reactions that involve the removal of two or more atoms to form a new molecule are known as
elimination reactions
 These reactions are reverse to addition reactions
 Organic compounds having good leaving groups readily undergo elimination
 Example: Alkyl halides and alcohols undergo elimination on treating with base or acid respectively.
 In elimination, a saturated compound converts into an unsaturated compound
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Types of organic reactions
Organic reactions are broadly classified into 4 classes
Addition
reactions
Substitution
reactions
Elimination
reactions
Rearrangement
reactions
 Reactions that involve the reorganization of atoms within the molecule to form a new structure are
known as rearrangement reactions
 These type of reactions are less common in organic chemistry
 These reactions are usually initiated in the presence of Lewis acids such as AlCl3, BF3, H+ etc.
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Oxidation and reductions reactions
 In organic chemistry, oxidation process involves the removal of hydrogens or addition of oxygen
atoms.
 Reduction process involves the removal of oxygen or addition of hydrogen atoms.
 Oxidation results in an increase in number of C-X or C-O bonds and decrease in number of C-H
bonds. Commonly used oxidants are H2CrO4, KMnO4, CrO3 etc.
 Reduction results in an increase in number of C-H bonds and decrease in number of C-X or C-O
bonds. Commonly used reductants are LiAlH4, NaBH4, H2 etc.
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Electronic displacements in covalent bonds
 The shared pair of electrons in a covalent bond will not be equally distributed instead they undergo
displacement towards one of the bonded atom and causes two types of polarizations that influence
the reactivity of a molecule.
 Permanent polarization: It occurs due to the presence of a polar atom or substituent in the carbon
chain. For example, inductive effect, Mesomeric effect and hyperconjugation.
 Temporary polarization: it occurs in the presence of attacking reagent only. For example,
electromeric effect.
 Inductive effect: The polarization of σ-bond due to the presence of a polar (EN) group is known as
inductive effect
 Inductive effect may be of two types with reference to hydrogen atom
+I effect
-I effect
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Electronic displacements in covalent bonds
 Positive inductive (+I) effect: If electrons
are displaced towards the carbon chain it
is known as +I effect. It occurs when atom
or group is having less electron attracting
capacity than H-atom
 Negative inductive (-I) effect: If electrons are
displaced away from the carbon chain it is known
as -I effect. It occurs when atom or group is
having more electron attracting capacity than Hatom
 Positive inductive (+I) groups: -NO2 > -CN > -COOH > -F > -Cl > -Br > -OR > COR > -C6H5 > -H
 Negative inductive (-I) groups: -(CH3)3C- > -(CH3)2CH- > CH3CH2- > CH3 > - H







Characteristics of inductive effect
It is a permanent effect
It occurs through σ-bonds only
It produces a partial dipole in the molecule and it is denoted by δ.
It can be observed through out the chain and its effect decreases with chain length
Applications: Inductive effect may be used to explain the stability of carbocations & carbanions
The acidity and basicity of organic compounds can be explained
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Electronic displacements in covalent bonds
 Electromeric effect: The shifting of π-electrons in a multiple bond in the presence of an attacking
reagent is known as electromeric effect
 It is a temporary effect and can be observed only in presence of attacking reagent
 Electromeric effect is of two types.
 1. Positive electromeric (+E) effect: If the π-electrons of a multiple bond are shifted to that atom
to which reagent gets attached is called +E effect
 2. Negative electromeric (-E) effect: If the π-electrons of a multiple bond are shifted away from
that atom to which reagent gets attached is called -E effect
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Electronic displacements in covalent bonds
 Resonance or Mesomeric effect: The polarity produced in the molecule due to resonance is
known as electromeric effect
 It is a permanent effect and can be observed in conjugated systems
 Mesomeric effect is more effective than inductive effect
 Mesomeric effect also two types.
 1. Positive mesomeric (+M) effect: If electrons are shifted towards the conjugated system it is
called +E effect
 2. Negative mesoomeric (-M) effect: If electrons are shifted towards the substituent it is called -E
effect
+ R effect in aniline
Atoms/group having lone pair show +R effect
Ex: -Cl, -Br, -OR, -OH, -NH2, -NHR, -NHCOR
-R effect in nitrobenzene
Atoms/group having +ve charge or multiple bond
show –R effect. Ex: -COOH, -CHO, -CN, -NO2, -NH3+
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Electronic displacements in covalent bonds
 Hyperconjugation
 The delocalization of sp3 C-H σ-electrons when it is bonded to an sp2 carbon atom is called
hyperconjugation. It is also known as σ-bond resonance.
 During hyperconjugation, no bond will be observed between C and H, thus it is also called no bond
resonance
 Hyperconjugation involves the overlap between filled σ-orbital and empty pz orbital of sp2 C
 It occurs only when an sp3 carbon having at least one C-H bond is bonded to an sp2 carbon
The concept of hyperconjugation was propsed by Baker
an Nathan in order to explain the stability of free
radicals, carbocations and alkyl substituted alkenes
Stability α number of resonance structures = (n-1)
Where n= number of α-hydrogens
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Electronic displacements in covalent bonds




The stability of free radicals and carbocations are as follows
Tertiart > Secondary > Primary > Methyl
This can be explaned using hyperconjugation as follows
As number of methyl groups increases around the free radical or carbocation, the number of alpha
H’s and number of hyperconjugated structures increases thus its stability increases
No. of α-H’s
0
2
6
9
No. of resonance
structures
0
3
7
10
Stability
LEAST
Hyperconjugation in ethyl carbocation
MOST
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P. Nagaraja
Assistant Professor in Chemistry
IIIT RK Valley, RGUKT
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