chemistry facts

Topics: Chemical bond, Atom, Benzene Pages: 9 (1242 words) Published: April 5, 2014
CONCEPTS IN ORGANIC CHEMISTRY
• Inductive Effect : Inductive effect is defined as
permanent displacement of shared electron pair
in a carbon chain towards more electronegative
atom or group.

Types of Inductive effect :
1.Negative Inductive Effect : (—I effect,
Electron withdrawing effect)
when an electronegative atom or group
(more electro negative than hydrogen)is
attached to the terminal of the carbon
chain
in a compound, the electrons
are displaced in the direction of the
attached atom or group.
-NO2 > -CN > -COOH > F > Cl > Br > I > OH > C6H5
>H

2. Positive Inductive effect : (+I effect, Electron
releasing effect)
When an electro positive atom or group
(more electro positive than hydrogen)is
attached to the terminal of the carbon
chain in a compound, the electrons are
displaced away from the attached atom
or group.
(CH3)3C- > (CH3)2CH- > -C2H5 > - CH3.

Applications of Inductive effect:
Inductive effect is useful in explaining the strength of
some organic acids and bases.
a) Effect of substituent on the acid strength of aliphatic
acids.
HCOOH > CH3COOH > (CH3)2CHCOOH
Reason : Acidic strength decreases as +I effect of the alkyl group increases.

b) O2NCH2COOH > FCH2COOH >CICH2COOH >
BrCH2COOH> ICH2COOH > CH3COOH
Reason : Acidic strength decreases as -I effect of the
group or halogen decreases.

Applications of Inductive effect:
c) Cl3CCOOH > Cl2CHCOOH> ClCH2COOH >
CH3COOH
Reason : Acidic strength decreases as the number of
halogen atoms decreases.
d) CH3CHClCOOH > CH2ClCH2COOH
Reason : Acidic strength decreases as the distance of
the halogen from carboxylic group increases.
e)
i.e., Benzoic acid is stronger than acetic acid.
Reason : due to –I effect of phenyl group.

Relative basic strength of amines
1. All aliphatic amines are more basic than ammonia.
e.g. Methyl amine is more basic than ammonia.
Reason : Due to +I effect of methyl group.
2. Aniline is weaker base than Ammonia.
Reason : Due to +R effect and –I Effect of phenyl
group.

Electromeric Effect

Electromeric effect is defined as the complete
transfer of electrons of a multiple bond towards
one of the bonded atoms at the demand of an
attacking reagent.
Note : a) It is shown by those compounds
containing multiple bond
b) It is a purely temporary effect & is
brought into play only at the
requirement of attacking agent.

Types of Electromeric Effect

+E effect : When displacement of electrons is
away from the atom or group.
e.g : addition of H+ to alkene.
-E effect : When displacement of electrons is
towards the atom or group.
e.g : addition of cyanide ion(CN-) to the carbonyl
group.

Mesomeric/ Resonance Effect
The flow of electrons from one part of a
conjugated system to the other caused by
phenomenon of resonance is called resonance
effect or mesomeric effect.
-M or -R effect : When the electron displacement
is towards the group.
e.g :-NO2 , -CHO,

+M or +R effect : When the electron
displacement is away from the group.
e.g :-OH , -OR,-Cl

SYNTHETIC ORGANIC CHEMISTRY

SYNTHETIC ORGANIC CHEMISTRY

SYNTHETIC ORGANIC CHEMISTRY

ISOMERISM-2
Stereo isomerism : Compounds which have
the same molecular formulae and same
structural formulae but differ in spatial
arrangement of the atoms or groups are
known as stereoisomers and phenomenon is
stereoisomerism.
1. Geometrical Isomerism
2. Optical Isomerism

1. Geometrical Isomerism : is due to
restricted or hindered rotation around the
double bond.

Conditions :
1. Molecule must have carbon-carbon double bond .
2. There must be two different atoms or groups
attached to each carbon atom of the double bond.

2. Optical Isomerism : Compounds have same
molecular & structural formulae but differ in
action towards plane polarised light.
e.g., Lactic acid(2-hydroxypropionic acid)
Optical activity : is the ability of chiral substance
to rotate the plane of plane polarized light....
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