Types of electronic effects with examples

1. ELECTRONIC EFFECTS
HIRA AROOJ

2. CONTENTS
• POLAR AND NON POLAR BONDS
• WHAT IS ELECTRONIC EFFECT?
• TYPES OF ELECTRONIC EFFECTS
1. INDUCTIVE EFFECT
2. MESOMERIC EFFECT
3. ELECTROMERIC
4. HYPERCONJUGATION
APPLICATIONS IN PHARMACY

3. NON POLAR BONDS POLAR BONDS
CL H
CL
V
V
c
V
V
V
V CL
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
NO Electronegative
difference
no charge building at poles
dont have dipole moment
van der waals interactions
Electronegative difference
charges building at their
poles
have dipole moment
involve in H bonding
-δ
+δ

4. ELECTRONIC EFFECT
An electronic effect influences the structure, reactivity, or properties of
molecule but is neither a traditional bond nor a steric effect.

5. INDUCTIVE EFFECT
The inductive effect is
a permanent state of
polarization. The
electron density in a σ
bond between two
unlike atoms is not
uniform. The electron
density is more dense
toward the more
electronegative of the
two atoms.
• Electron withdrawing
• more electronegative atom or group, and electron
density is higher there
• nitro (−NO2),(−NO2), cyano (−CN),(−CN), carboxy
(−COOH),(−COOH), ester (−COOR),(−COOR), and
aryloxy (−OAr).(−OAr)
- I
• electron donating
• less electronegative atoms of the molecule
by electron-releasing groups
• The alkyl groups are usually considered
electron-releasing groups
+ I

6. INDUCTIVE EFFECT
The inductive effect is
a permanent state of
polarization. The
electron density in a σ
bond between two
unlike atoms is not
uniform. The electron
density is more dense
toward the more
electronegative of the
two atoms.
• Electron withdrawing
• more electronegative atom or group, and electron
density is higher there
• nitro (−NO2),(−NO2), cyano (−CN),(−CN), carboxy
(−COOH),(−COOH), ester (−COOR),(−COOR), and
aryloxy (−OAr).(−OAr)
- I
• electron donating
• less electronegative atoms of the molecule
by electron-releasing groups
• The alkyl groups are usually considered
electron-releasing groups
+ I

7. • inductive effect is distance dependent phenomena
upto 3 to 4 atoms
• The inductive effect is permanent
• These relative inductive effects are measured with
reference to hydrogen:
• NO2>COOH>F>Cl>Br>I>OR>OH>C6H5(Benzene)>H>Me3C−>Me
2CH−>MeCH2−>CH3−.NO2>COOH>F>Cl>Br>I>OR>OH>C6H5(Be
nzene)>H>Me3C−>Me2CH−>MeCH2−>CH3−.

8. Applications
Acidic strength
of aliphatic
carboxylic acids
The effect on
dipole moment
and bond
length
Stability of alkyl
carbocation,
carbanions,
and carbon-
free radicals.
The relative
strength of
organic bases
basic strength ∝+I effect
CH3 -NH2 > NH3
Greater -I effect greater dipole moment
CH3 NO2> CH3COOH> CH3F> CH3OH

9. MESOMERIC EFFECT
The polarity developed
between atoms of a
conjugated system by the
electron transfer or pi–bond
electron transfer is known as
the Mesomeric effect. In
simple terms, we can describe
mesomeric effect occurs when
π electrons move away from or
towards a substituent group in
a conjugated Orbital system.
CH2 = CH - CH2
CH2 - CH= CH2
RESONANCE
The possibility of shifting pi electron is known as resonance.
CH2 = CH - CN
MESOMERIC EFFECT
❌
✔

10. “Any functional group which donates or withdraw electrons in
a conjugated system through resonance is mesomeric effect.
”
+M effect (Positive mesomeric effect -M Effect (Negative mesomeric effect)
Significance of Mesomeric effect
It describes the distribution of the charge in the compound, helps to decide the point at which
electrophiles or nucleophiles attack.
Useful in describing physical characteristics such as dipole moment, bond length.
-NO2, -CHO, and -CN
-NH2, -OH, and -SH

11. ELECTROMERIC EFFECT
An intramolecular movement of electrons from a pi bond to another atom in
the molecule due to attack by a reagent. It is temporary and reversible
Positive Electromeric Effect
(+E effect)
Negative Electromeric Effect
(-E effect)

12. HYPERCONJUGATION
Hyperconjugation helps
explain the stability of alkyl
radicals. It involves the
delocalization of σ-electrons
belonging to the C-H bond of
the alkyl group attaching to
an atom with an unshared pp
orbital.
The more the
hyperconjugative hydrogen,
the more is the stability.
VACANT P
ORBITAL
SP3 CARBON
SP2
CARBOCATION
SP3 SIGMA
BOND B/W
C-H

13. C+
H
C
H
H
SP3 CARBON SP2 CARBOCATION
EMPTY P OTBITAL

14. C
H
C
H
H
SP3 CARBON SP2 CARBOCATION

15. C
H
C
H
H
SP3 CARBON SP2 CARBOCATION
H
H

16. APPLICATIONS OF HYPERCONJUGATION
1.Stability
of
alkenes
Stability of
alkenes increases
with the increase
in alkyl groups
containing H-atoms
on the double bond
due to increase in
number of
hyperconjugative
structures.
2.Stability
of
carbocations
Order of
stability is
tertiary>
secondary>
primary>
methyl
3.Stability
of
free
radicals
Order of
stability is
tertiary>
secondary>
primary>
methyl

17. APPLICATIONS
IN PHARMACY
Stability of
drug
Increasing
therapeutic
effect/
efficacy
Decreasing
adverse drug
reactions
Drug
repositioning
Drug
interaction
with biological
medium
Drug
designing/
Synthetic
drug
Production

18. Thankyou..!