Organic chemistry is the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds.

1. ORGANIC CHEMISTRY
Tasmina Ferdous Susmi
Jashore University of Science and Technology,

2. Topics of the presentation:
• Bond and its classification.
• Bond dissociation energy.
• Friedel-Craft reaction.
• Wurtz reaction.

3. Bond and its classification.

4. Chemical Bond
Mutual electrical attraction between the nuclei and
valence electrons of different atoms that bind the
atoms together.
Condition:
• An attraction force between atoms.
• Allows the formation of chemical substances.
• Contains two or more atoms.

5. Causes of formation of chemical bonds:
• Most atoms are instable.
• To become stable.
• Making bond with other atoms and perform the octal
rule.

6. Types of chemical bond
Chemical bond is mainly of four in number.
1. Electrovalent or Ionic bond
2. Covalent bond.
3. Co-ordinate covalent bond.
4. Metallic bond.

7. There are also some other bonds.
1. Hydrogen bond.
2. Van der waals force.
3. Sigma bond and Pi bond.
Strength of the chemical bonds are various.
1. Strong bonds.(Ionic and covalent.)
2. Weak bonds.(Hydrogen bond, dipole-dipole
interactions.)

8. Ionic Bond
A chemical bond formed between two ions with opposite
charges.
Example: NaCl, KCl.

9. Conditions of Formation of Ionic Bond
• Low ionization Energy.
• High electron affinity.
• High lattice energy.

10. Properties Of Ionic Bond
• Crystalline solid.
• High melting point.
• Soluble in water.
• Well defined crystals.
• Molten from conducts electricity.
• No odor.

11. Covalent Bond
A chemical bond is a chemical link between two atoms in
which electrons are shared between them.
Example: Water, H2, O2, CH4, NH3.

12. Properties Of Covalent Bond
• Lower melting point.
• Lower boiling point
• Liquids or gases.
• Soft- easier to crush.
• Are not conductors of electricity.

13. Co-ordinate Covalent Bond
A bond, in which a pair of electrons from one atom is
shared by two atoms. Properties are same as covalent
bond.
Example:NH4 ion.

14. Presence of Different types of bonds in a
Same Compound
Example:NH4Cl

15. Metallic Bond
A bond that results from the attraction between metal
atoms and the surrounding sea of electrons.

16. Properties of Metallic Bond
• High melting and boiling point.
• Conduct electricity and heat.
• Hard and dense.
• Can be hammered into shapes ( malleable).
• Can be drawn out into wires (ductile).

17. A bond with electrostatic between hydrogen atoms
bonded to small strongly electronegative atoms (N,O
and F) and the lone pair electrons on these
electronegative atoms.
Example:H2O.
Hydrogen Bond

18. Properties of Hydrogen Bond
• Cohesion- sticks to other water.
• Adhesion- sticks to other polar substances.
• Surface tension.
• High specific heat- does not change temperature
easily.

19. Importance of Hydrogen Bond
• Source of unique properties of water.
• Structure and function of proteins.
• Structure and function of DNA.
• Structure and function of Polysaccharides.
• Binding of substrates to enzymes.

20. Importance (continued)
• Binding of hormones to receptors.
• Matching of mRNA and tRNA.
• Presence of H bond in cotton fiber.
• Presence of H bond in bone, cartilage and skin.

21. Van der waals Force
An interaction named after Dutch scientist Johannes
Diderik van der Waals, are week interactions caused by
Momentary changes in electron density in a molecule.
Example: CH4, C6H6.

22. Properties of Van der waals Force
• Non directional.
• Weaker than Hydrogen bond.
• Having low melting point for solids.
• Available valence electrons.

23. Sigma Bond
The strongest type of covalent bond formed by head on
overlapping between atomic orbitals.
Example:H2, CH4.

24. Characteristics of Sigma Bond
• Formed by the axial overlap of atomic orbitals.
• Can be of S-S, S-P, P-P orbitals.
• Stronger for larger extent overlapping.
• Density of electrons more.
• Having fixed direction of stretches.

25. Pi Bond
A type covalent bond formed between two neighboring
atoms unbonded P orbital.

26. Characteristics of Pi Bond
• Formed by the sidewise overlap of atomic orbitals.
• Involves of overlap of P orbitals only.
• Weaker for smaller extent overlapping.
• Density of electrons less.
• Does not occur in hybridized orbital.

27. Bond Dissociation Energy

28. Bond Dissociation Energy
The amount of energy consumed or liberated when a
bond is broken or formed is known as the bond
dissociation energy.

29. Measurement of BDE
Two types:
• Homolysis: One electron to each fragment.
• Heterolysis: Both electron to one fragment.

30. Bond Energy
Defined as the amount of energy required to break a
bond in a molecule.
Bond energy is the average of all bond dissociation
energy.
For Example: In CH4 removing H,
BDE(CH3-H)= 104 Kcal/mol.
BDE(CH2-H)= 106 Kcal/mol.
BDE(CH-H)= 106 Kcal/mol.
BDE(C-H)=81 Kcal/mol.
The bond energy is 99 Kcal/mol.

31. Reaction

32. A French chemist, Charles Friedel, and his American
collaborator James M Craft discovered new methods for
the preparation of alkylbenzenes (ArR) and acylbenzenes
(ArRCOCl) in1877.

33. What is the purposes of the reaction?
• Formation of C-C bond to atomic ring.
C
C
C–C bond forms

34. Friedel-Craft Reaction
There are 2 types of friedel craft reaction.
• Alkylation.
Alkylation substitution with R, e.g.
• Acylation.
Acylation substitution with R-CO, e.g.
R
C
R
O

35. Friedel-Craft Alkylation.
Reagent and condition:
• Alkyl chloride, RCl .
• Halogen carrier catalyst, e.g. AlCl3.
• Anhydrous conditions.
R
+ RCl
AlCl3 catalyst
+ HCl

36. General mechanism of Friedel-Craft
alkylation reaction.

37. Friedel-Craft Acylation.
Reagent and condition:
• Acyl chloride, RCOCl .
• Halogen carrier catalyst, e.g. AlCl3.
• Anhydrous conditions.
C
+ RCOCl
AlCl3 catalyst
+ HCl
O
R

38. General mechanism of Friedel-Craft
acylation reaction.

39. Limitation of Friedel-Craft reaction.
• Reaction limited to alkyl halide; aryl or vinyl halide do
not react.
• Reaction does not occur on rings containing strong
electron.
• Multiple substitutions often occur.
• Carbocation rearrangements can occur, particularly
with primary alkyl halide.

40. Wurtz-Fittig Reaction.
The Wurtz reaction for the synthesis of alkanes was
extended by Fittig in 1864, to synthesis of alkyl aromatic
hydrocarbon.

41. Wurtz-Fittig Reaction.
Reagent and condition:
• Alkyl halide, R-X .
• Dry ether.
• Sodium- Na.
+ 2Na + R-X + 2NaX
R

42. General Mechanism of wurtz-Fittig Reaction: