Organic Chemistry

1. Organic Chemistry Dr Manal F. AbouTaleb

2. Introduction to Organic Chemistry 1What is Organic Chemistry? 2The Unique Nature of Carbon 3Classification of Organic Compounds

3. What is Organic Chemistry Organic Chemistry:The chemistry of the compounds ofcarbon • Carbon compounds: DNA, proteins in our body, carbohydrates, wool, cotton, petrol, medicines, pesticides, etc. • Organic chemicals • make our life easy • but also cause serious environmental problems • (e.g. organic compounds used as aerosol propellent damage the ozone layer, insecticide is harmful to human

4. What is Organic Chemistry Inorganic Compounds Organic Compounds obtained from living organisms obtained from non-living sources Development of Organic Chemistry as a Science In the past …, Chemistry

5. What is Organic Chemistry In 1828, Wohler (a German chemist) (Inorganic compound) (Organic compound) Redefining …... Organic chemistry is the study of carbon compounds except carbon monoxide, carbon dioxide, carbonates, hydrogencarbonates, carbides and cyanide.

6. What is Organic Chemistry Fractional distillation / destructive distillation Natural Sources of Organic Compounds Alkanes / Alkenes / Alkynes / Aromatic hydrocarbons Crude oil / coal Carbohydrates / Proteins / Fats / Vitamins / Antibiotics Living things

7. The Unique Nature of Carbon Ability to Catenate Carbon atoms can link themselves together to form chains of varying length, branched chains and rings of different sizes Catenation: The ability of atoms in forming stable bonds with itself and joining up in chains or rings. e.g.

8. 24.2 The Unique Nature of Carbon Carbon (ground state) Carbon (excited state) Ability to Form Multiple Bonds • Electronic configuration of carbon (ground state) : 1s22s22p2 • Each carbon atom has four unpaired electrons when excited • tend to form 4 covalent bonds

9. The Unique Nature of Carbon

10. The Unique Nature of Carbon Example 1 Would you expect silicon, which is just below carbon in the Periodic Table, to catenate to form diverse molecular structures? Explain your answer. Answer Solution: Silicon, unlike carbon, does not catenate to form diverse molecular structures. Carbon is able to catenate because carbon atoms have a relatively small atomic size. This enables a carbon atom to formstrong covalent bonds with other carbon atoms. However, due to the greater atomic size of silicon, its ability to catenate is much lower than that of carbon.

11. The Unique Nature of Carbon The electronic configuration of sulphur is 1s22s22p63s23p4. It has only two unpaired electrons. Its atomic size is largerthan that of carbon. So it has a much lower tendency to catenate than carbon. Check Point 1 Would you expect sulphur, which has an electronegativity value very close to carbon, to catenate? Why? Answer

12. Classification of Organic Compounds Functional Groups The compounds in a particular family are characterized by the presence of a certain arrangement of atoms called a functional group A functional group is defined as an atom or a group of atoms that carry out chemical reactions in many organic compounds and effectively determines the chemical properties of an organic compound.

13. and Classification of Organic Compounds e.g. have similar chemical properties because they contain the same functional group –OH. They are classified into the same homologous series — Alcohols.

15. Classification of Organic Compounds R = CnH2n+1 –

16. Classification of Organic Compounds R = CnH2n+1 –

17. Classification of Organic Compounds R = CnH2n+1 –, X = F, Cl, Br or I

18. Classification of Organic Compounds R = CnH2n+1 –

19. Classification of Organic Compounds Number of carbon atom(s) IUPAC name Molecular formula Condensed structural formula Structural formula 1 Methane CH4 CH4 2 Ethane C2H6 CH3CH3 3 Propane C3H8 CH3CH2CH3 4 Butane C4H10 CH3CH2CH2CH3 A homologous series is a series of compounds that have the same functional group, and each member differs from the next member by a – CH2 – unit in their formulae.

20. Classification of Organic Compounds

21. Classification of Organic Compounds Chemical properties Members in the same series can be represented by a general formula. e.g. General formula of alkanes: CnH2n+2 General formula of alcohols: CnH2n+1OH Functional group of an organic compound Members of a homologous series have similar chemical properties

22. Classification of Organic Compounds Homologous Series The physical properties change gradually along the homologous seriese.g. the longer the carbon chain in molecule ( or the greater the molecular mass) the greater the attractive force between molecules  the higher the melting point and boiling point

23. Classification of Organic Compounds Some physical properties of the first 20 members of straight-chain alkanes

24. Classification of Organic Compounds Some physical properties of the first 20 members of straight-chain alkanes

25. Classification of Organic Compounds • Solution: • Carbon-carbon double bond ( ) and chloro ( ) group Example 2 Identify the functional group(s) in the following compound: (a) Answer

26. Classification of Organic Compounds Solution: (b) Carbonyl group ( ) Example 3 Identify the functional group(s) in the following compound: (b) Answer

27. Classification of Organic Compounds Solution: (c) Amino group ( ) and carboxyl group ( ) Example 4 Identify the functional group(s) in the following compound: (c) Answer

28. Classification of Organic Compounds Example 5 To which homologous series does each of the following compounds belong? (a) Answer Solution: (a) Ester

29. Classification of Organic Compounds Example 6 State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answers. (b) Answer Solution: (b) Yes, both of them are alcohols.

30. Classification of Organic Compounds Example 7 State whether each of the following pairs of compounds belongs to the same homologous series. Explain your answers. (c) Answer Solution: (c) No, the first one is an amide and the second one is an amine.

31. Classification of Organic Compounds (b) – OH (hydroxyl) and – O – (oxy) groups Check Point 2 (b) Identify and name the functional groups in glucose which has the structure: Answer

32. Chemical Bonding Problems and questions — How is a molecule or polyatomic ion held together? Why are chemical bonds important?

33. Important concepts in chemical bonding • The attractive force which holds together the constituent particles (atoms, ions or molecules) in chemical species is known as chemical bond. • Each bond is made up of two electroms • Tendency of atoms of various elements to attain stable configuration of eight electrons in their valence shell is the cause of chemical combination. • The principle of attaining a maximum of eight electrons in the valence shell or outermost shell of atoms is known as octet rule. • The tendency of an atom to take part in chemical combination is determined by the number of valence electrons (electrons in the outermost shell of an atom). • The atoms acquire the stable noble gas configuration of having eight electrons in the outermost shell (called octect rule) by mutual sharing (covalent bond which is usually between two non metals) or by transfer of one or more electrons (ionic bonds which is usually between a metal and a nonmetal). N.B.: there are other minor types of chemical bonding that will not be discussed here. • The valency of an element is (number of electrons an atom loses, gains or mutually shares to attain noble gas configuration).

34. The structural theory • 1. The atoms can form a fixed number of bonds (valence)

35. Review of Valence Electrons Number of valence electrons of a main (A) group atom = Group number

36. Two Main Types of Chemical Bonding Covalent Bonds; single or multiple polar or non polar Ionic Bonds

37. Covalent Bond

38. Characteristics of Covalent Compounds Covalent compounds results when two atoms share valence electrons between them. • The covalent compounds do not exist as ions but they exist as neutral molecules: This is due to there is no transfer of electrons from one atom to another and therefore no charges are created on the atom. 2. Most of the covalent molecules are non polar and are soluble in nonpolar solvents like benzene, ether etc and insoluble in polar solvents like water. Carbon tetrachloride (CCl4) is a covalent nonpolar molecule and is soluble in benzene. • Some of them are polar due to sometimes in a covalent bond the electrons are not shared equally between the two atoms thus, one of the atoms partially "pulls" the bonding electrons toward itself, creating an unequal sharing of those bonding electrons. This is called a POLAR COVALENT BOND.

39. Ionic Bonds • Ionic compounds are formed when one atom gains a valence electron from a different atom, forming a negative ion(anion) and a positive ion (cation) respectively. These oppositely charged ions are attracted to each other, forming an ionic bond. Therefore ionic bonds are usually between metalsand nonmetals ; opposite ends of the periodic table.

40. Sodium chloride Sodium Chloride (NaCl) is a bonding of the Na+ ion and the Cl- ion. Sodium lets Chlorine use its valance electron