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Chemistry. Alkane Session objectives 1.Methods of preparation 2.Kolbe’s electrolysis 3.Physical Properties and Chemical properties 4.Halogenation 5.Refining.

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Presentation on theme: "Chemistry. Alkane Session objectives 1.Methods of preparation 2.Kolbe’s electrolysis 3.Physical Properties and Chemical properties 4.Halogenation 5.Refining."— Presentation transcript:

1 Chemistry

2 Alkane

3 Session objectives 1.Methods of preparation 2.Kolbe’s electrolysis 3.Physical Properties and Chemical properties 4.Halogenation 5.Refining of petroleum 6.Octane number

4 General characteristics of alkene Paraffins General formula C n H 2n+2 sp 3 hybridisation C–C bond length A 0 Chemically unreactive

5 Methods of preparation Wurtz reaction Follow mainly free radical mechanism Useful in preparing an alkane containing even number of carbon atoms Stepping up reaction

6 Frankland reaction

7 Decarboxylation of sodium or potassium salt of fatty acid For example

8 Kolbe’s electrolysis At anode

9 Kolbe’s electrolysis For example At anode

10 From Grignard reagent (RMgX) From unsaturated hydrocarbons Sabatier-Senderens reduction

11 Methods of preparation From alkyl halides R – I > R – Br > R – Cl > R – F From aluminium carbide Corey House reaction

12 Physical Properties Boiling point:

13 Physical Properties Melting point: Zigzag arrangement of carbon atoms in alkanes

14 Physical Properties (a) Alkane having even carbon atom (a) Alkane having odd carbon atom Symmetrical –higher melting point unsymmetrical – lower melting point

15 Chemical properties Combustion Oxidation Halogenation CH 4 + Cl 2 CH 3 Cl + HCl

16 Mechanism Initiation Propagation Termination

17 Features of Halogenation F 2 > Cl 2 > Br 2 > I 2. Attack of or on an alkane is selective Order of reactivity is 3° > 2° > 1°

18 Features of Halogenation

19 Nitration

20 Features of Halogenation Sulphonation Isomerization

21 Features of Halogenation Aromatization

22 Refining of petroleum Sources of hydrocarbons Petroleum Aliphatic hydrocarbons Coal Aromatic hydrocarbons

23 Refining of petroleum FractionBoiling rangeApproximate composition uses Gaseous113 to 303 KC 1 - C 5 (2%)For producing carbon black and in preparation of ammonia, methyl alcohol and gasoline. Petroleum ether or Ligroin 303 to 363C 5 - C 7 (2%)solvent for oils, fats, rubber and in dry cleaning. Gasoline or petrol 343 to 473C 7 - C 12 (32%)Mainly as a motor fuel.

24 Refining of petroleum Kerosene448 to 548C 12 - C 15 (18%)Illuminant fuel and for preparing petrol gas. Gas oil, fuel oil and diesel oil 523 to 673C 15 - C 18 (20%)In furnace oil, fuel for diesel engines and in cracking. Lubricating oils and petroleum jelly 623 and upC 16 and upUsed mainly as lubricants. FractionBoiling range Approximate composition uses

25 Cracking

26 Synthetic petrol Fischer-Tropsch process Bergius process

27 Octane number Percentage by volume of iso-octane in the mixture of iso-octane and n- heptane which has the same anti- knocking qualities as the fuel under examination.

28 Octane number Straight chain alkanes have low octane numbers. The greater the length of the chain, lower is the octane number. Straight chain alkenes and alkynes, and also cyclic alkanes have higher octane numbers than their corresponding alkanes. Branched chain hydrocarbons have high octane numbers. Aromatic hydrocarbons have very high octane numbers.

29 Class exercise

30 Class exercise 1 Ethyl iodide + n-propyl iodide mixture of hydrocarbon. Which of the following hydrocarbons will not be formed? (a) Butene(b) n-hexane (c) n-pentane(d) n-butane

31 Solution Hence, the answer is (a).

32 Class exercise 2 Product is Hence, the answer is (a). Solution:

33 Class exercise 3 Which of the following carbides are used in preparation of methane by action of water? (a) CaC 2 (b) Al 4 C 3 (c) Si C(d) All of these Solution: Hence, the answer is (b).

34 Class exercise 4 Which of the following reactions will give maximum yield? Solution: Reaction proceeds via free radical mechanism and excess of C 2 H 6 is needed as it forms various products. Hence, the answer is (b).

35 Class exercise 5 Which of the following compounds will have the highest heat of combustion? (a)C 3 H 6 (b) C 5 H 12 (c) C 6 H 14 (d) C 10 H 22 Solution: Hence, the answer is (d). It has highest number of carbon and hydrogen atoms.

36 Class exercise 6 Which of the following reactions will give unsymmetrical alkanes in good yield? (a) Frankland reaction (b) Wurtz reaction (c) Corey House reaction (d) All of these Frankland and Wurtz reaction gives alkane having even number of carbon atoms. Solution: Hence, the answer is (c).

37 Class exercise 7 Which of the following is true for above reaction? (a) Compound X and Y are formed in equal quantities (b) Compound Y is formed in excess (c) Compound X is formed in excess (d) None of these

38 Solution Hence, the answer is (b).

39 Class exercise 8 The monochlorination of an alkane (molecular formula C 8 H 18 ) gives only one product. The IUPAC name of alkane is (a) neo octane (b) iso octane (c) 2, 2, 3-trimethylpentane (d) 2, 2, 3, 3-tetramethylbutane Solution: Hence, the answer is (d).

40 Class exercise 9 Hydrolysis of calcium carbide gives a solution with pH (a) 0(b) 7 (d) 3 Solution: Hence, the answer is (c). pH is more than 7 due to formation of Ca(OH) 2.

41 Class exercise 10 Sodium benzoate + sodia lime X. X is (a) ethane (b) benzene (c) ethene(d) propane Solution: Hence, the answer is (b).

42 Thank you


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