Hydrogen bonding occurs when a hydrogen atom bonded to a highly electronegative atom such as nitrogen, oxygen or fluorine interacts with another electronegative atom. This leads to compounds having higher boiling points than expected due to the need to overcome hydrogen bonding interactions. Hydrogen bonding plays important roles in determining the structure of materials like DNA and proteins and was also utilized in the hydrogen bomb to dramatically increase its explosive yield.

1. 02
02
HYDROGEN BONDING
&APPLICATIONS
By-Nikhil Sharma
Md Azharuddin
Yash
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2. HYDROGEN BONDING
• Hydrogen bonding is a special case of dipole-dipole interactions.
• When hydrogen is bonded to a highly electronegative atom (such as
nitrogen, oxygen, fluorine), the bonding electron pair is drawn
towards the electronegative atom.
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3. Hydrogen bonding
F H F H.....
δ- δ+ δ- δ+
Hydrogen has no inner shell electron and is very small in size, the
positive charge density developed is high
The nucleus of hydrogen atom is exposed to attraction by nearby
electron cloud, a lone pair electrons on the electronegative atom
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4. H
F
.
..
.
.
.
H
F
.
..
. .
.
H
F
.
..
.
.
.
H
F
.
..
.
.
.
Hydrogen Bonding in Hydrogen
Fluoride
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5. Hydrogen bonding
• More Examples
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6. CONDITION FOR H-BONDING
– A hydrogen atom must be directly bonded to a highly
electronegative atom (e.g. F, O and N)
– An unbonded pair of electrons (lone pair electrons) is
presented on the electronegative atom
 The size of the electronegative atom should be small. The
smaller the size ,the greater is the electrostastics attraction.
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7. NOTES
• Intermolecular hydrogen bond:
 Hydrogen bond formed between two molecules
 Intramolecular hydrogen bond:
 Hydrogen bond formed between
two different atoms in the
same molecule
 Intermolecular hydrogen bond is stronger than van der
Waals’ forces
N
O
O
O
H
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8. Strength of hydrogen bond
• Hydrogen bonding is very weak bond.The strength of
hydrogen bond is intermediate between the weak van
der waal’s forces and the strong covalent bonds.Thus
whereas the bond dissociation energy of a covalent bond
is 209-418 Kj/mol.That for H-bond is only 12.6-41.8
kj/mol.
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9. Diff. between H-bond &Covalent
bond
H-bond
 It involves dipole-dipole
attractive interactions.
 It is formed between a
hydrogen and a highly
electronegative atom such as
F,O,N.
 The strength of this bond is
very small.
Covalent bond
 It involves sharing of electrons.
 It is formed between two
electronegative atoms which
may be out of the same
element or of different
elements .
 The bond strength of this bond
is sufficiently high.
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10. Consequences of H-bond
High melting & boiling points:
The compound having H-bond show abnormally high melting and
boiling point.
Due to the containing hydrogen
bond to the fact that some extra
energy is needed to break these
bonds.
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11. Q1: Why do NH3, H2O and HF have
abnormally high boiling point?
• Explanation:
– N, O and F are highly electronegative atoms
• Formation of intermolecular hydrogen bonds in their hydrides.
– Intermolecular hydrogen bonds are much stronger than van der
Waals’ forces
– More energy is needed to break the hydrogen bonds in NH3, H2O
and HF
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12. Q2: Explain why the order of boiling point is
H2O > HF > NH3
 Explanation
 H2O can form 2 hydrogen bond per molecule
 NH3 and HF can form only 1 hydrogen bond per molecule
 The boiling point of H2O is higher than NH3 and HF
No. of H
atoms
available for
hydrogen
bond
formation
No. of lone
pair
electrons
available
No. of
hydrogen
bonds can
form per
molecule
NH3 3 1 1
H2O 2 2 2
HF 1 3 1
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13. Q2: Explain why the order of boiling point is
H2O > HF > NH3
– Comparing N and F, F is more electronegative
– The intermolecular hydrogen bond formed between HF
molecules is stronger than NH3
– HF has a higher boiling point than NH3
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14. Explanation of lower density of ice than
water
• In case of solid ice,the hydrogen bonding gives rise to
a cage like structure of water molecules as shown.As
a matter of fact ,each water molecule is linked
tetrahedrally to four water molecules tetrahedrally.
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15. This section of
water is frozen
This section of
water is liquid
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16. APPLICATIONS
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17. Importance of Hydrogen Bonding in Physical
Phenomena
• Boiling Point and Solubility of Alcohols
– The boiling points of alcohols
are higher than the thiols
because there are
intermolecular hydrogen bonds
between alcohol molecules,
but only dipole-dipole
interactions between
molecules of thiols
Alcohols:
Thiols:
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18. • Alcohols of low molecular masses are soluble in water
because they can form intermolecular hydrogen
bonds with water molecules
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19. Importance of Hydrogen Bonding in Biochemistry
• Secondary structure Of Protein
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20. Hydrogen Bonding in DNA
DNA stands for
Deoxyribose Nucleic Acid
DNA contains genetic
information
Consists of 2
macromolecular strands
spiralling around each
other in the form of a
double helix
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21. H-BOMB
• The hydrogen bomb is a nuclear weapon that used
a mixture of fission and fusion (Hydrogen fuel) to
produce a massive explosion
• It produces 700-times the energy released by the
bombs exploded in Hiroshima and Nagasaki.
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22. Nagasaki MushroomNagasaki Mushroom
cloud.cloud.
13 km high!13 km high!
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23. • It is made up of essentially, 3 things:-
1.Implosion Type Fission Bomb:- It contains a core of
U-235 and a tamper of U-238
2.Fusion Bomb:- A cylinder containing a core rod of
Plutonium-239 surrounded by lithium-duterate fuel
with a tamper of U-238.
3.Polystyrene foam:- The empty spaces are filled by it.
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