Secondary bonding includes dipole forces, induction forces, van der Waals forces, and hydrogen bonding. These weaker intermolecular forces influence the properties of organic compounds. Dipole forces are caused by partial charges on polar bonds and affect properties like melting point. Hydrogen bonding is the strongest secondary bond and significantly increases boiling points, as seen when comparing methanol, ethanol, and water. Hydrogen bonding also improves the mechanical properties of materials like nylon.

1. ORGANIC CHEMISTRY FOR TEXTILE
2. Bonding in organic compounds
L3: Secondary bonding

2. PRIMARY AND
SECONDARY BONDING
 A secondary bond is
that where no true
sharing or transfer of
electron does occur
while primary bond is
formed by sharing or
transfer of electron.
 Primary bonding forces
are short range strong
forces, but the
secondary bonding
forces are long range
weak forces.
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3. SECONDARY BONDING
 The following types of secondary bonding occurs in
organic compounds:
 Dipole forces
 Induction forces
 van der Waal’s forces
 Hydrogen bonding
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4. DIPOLE FORCES
 When two atoms having
difference in electronegativity
are bonded together, the
resulting bond is not neutral but
bears partial negative and
positive charges or polarity.
Such polar bonds are said to
have dipole. The greater the
difference of electronegativity
the greater the intensity of
charges and greater the dipole.
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5. EFFECT OF DIPOLE FORCES
 Since similar charges repel and
opposite charges attract each
other, the dipole forces effect
the orientation of molecules in
any material.
 The orientation of molecules
strongly effect physical
properties of materials. For
e.g. the melting and boiling
point will rise.
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6. EFFECT OF DIPOLE FORCES
 Due to highly polar
nature PVC is very
hard material while
polyethylene is soft
and flexible.
 The melting point of
polyethylene is 110 C
while that of PVC is
above 200 C.
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7. EFFECT OF DIPOLE FORCES
 This effect is very
prominent in polymers
where these forces effect
the strength of polyester
(PET).
 The dipole forces bind the
polymer chains together
and enhance the
mechanical properties in
polyvinyl chloride (PVC).
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8. INDUCTION FORCES
 When a molecule having a dipole comes near a
non polar molecule, the later experiences slight
charge separation due to interaction with polar
molecule. The forces acting due to such induced
charge are called induction forces
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9. INDUCTION FORCES
 Induction forces are weak and temporary forces
and they die as and when the permanent dipole
moves away.
 however these forces do effect the properties of
polymers to some extent.
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10. VAN DER WAAL’S FORCES
 In any material all the molecule
attract one another since the
nucleus of each molecule exert
slight attraction on electrons of
the other molecules, so that the
molecule come nearer to one
another. However, the repulsion
between the electrons of different
molecules becomes prominent if
they come too close to one other
and thus keeps them at a certain
distance. The forces acting to
keep the molecules together are
called van der Waal’s forces.
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11. EFFECT OF VAN DER WAAL’S FORCES
 Due to van der Waal’s forces the free movement of
molecules in a substance is effected. Thus
stronger the forces the more restricted the
movement.
 If there were no van der Waal’s forces all molecule
of any matter would move away from one another
and everything would exist only in gaseous state.
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12. EFFECT ON MELTING, BOILING AND
SOLUBILITY
 The melting points, boiling points and physical
state of materials is effected by Van der Waal’s
forces.
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13. CHANGE OF STATE
 When a material changes from one state to
the other state it absorbs or releases
energy, hence the kinetic energy of it’s
molecules changes.
 When changing from solid to liquid state the
kinetic energy of molecules increases and
they tend to move away from one another to
a greater distance. The van der Waal’s
forces thus oppose this change in kinetic
energy, therefore, greater the intermolecular
forces greater will be the energy required to
change the state and higher will be it’s
melting point. 13

14. HYDROGEN BONDING
 When a hydrogen bonded to a
molecule comes in vicinity of
another atom having a lone
pair, like oxygen, on another
molecule, it forms secondary
bond with it. For example the
hydrogen of a water molecule
forms secondary bond with
oxygen of the other water
molecule.
 The hydrogen bond is a not a
primary bond but near to it in
strength and strongest of all
secondary bonds.
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15. HYDROGEN BONDING
EFFECT ON PHYSICAL PROPERTIES
 Hydrogen bonding exerts
a strong effect on physical
properties of materials like
boiling and melting point.
Boiling point of methanol is
64.5 ˚C, that of ethyl
alcohol is 78 ˚C, while that
of water is 100 ˚C.
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16. HYDROGEN BONDING
 In polyamides like nylon, wool, silk, inter-chain hydrogen
bonding enhances the mechanical properties.
 The extraordinary strength of nylon is due to the heavy
inter-chain hydrogen bonding.
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