1. Chemistry

2. Purification And Characterisation of Organic Compounds - 1
Session
Purification And Characterisation of Organic Compounds - 1

3. Session Opener

4. Session Objectives

5. Session objectives Introduction — necessity of purification.
Methods of purification of organic compound.
Crystallisation
Fractional crystallisation
Sublimation
Distillation
Fractional distillation
Steam distillation
Vacuum distillation
Differential extraction
Chromatography

6. Session objectives 3. Detection of elements (Qualitative analysis)
(a) Detection of carbon
(b) Detection of hydrogen
(c) Detection of nitrogen
(d) Detection of sulphur
(e) Detection of halogen
(f) Detection of oxygen

7. Purification Filtration Crystallization Sublimation Distillation
Differential extraction
Chromatography

8. Filtration Only one of the compounds is soluble in the given solvent
Urea and Naphthalene
Benzoic acid and anthracene

9. Crystallization
Most common method for purification of solid organic compounds.
Impurities and organic compound have different solubilities in the given solvent.

10. Crystallization
v The organic compound should be insoluble or sparingly soluble in the solvent at room temperature but readily soluble in hot conditions.
v The impurities should be insoluble in the solvent even in hot conditions.
v The organic compound should not react with the solvent.

11. Crystallization
The mixture of benzoic acid (water soluble) and naphthalene (water insoluble) purified by.

12. Crystallization
How will you separate mixture of benzoic acid and napthalene ?
benzoic acid (water soluble ) and
napthalene (water insoluble)

13. Fractional crystallization
Difference in solubilities of organic compounds and impurities are very less.
eg. urea and copper sulphate.

14. Sublimation
Used to separate volatile organic compounds from non volatile impurities e.g. Naphthalene, benzoic acid, anthracene, camphor.

15. Questions

16. Illustrative problem A mixture of benzene and aniline
can be separated by
alcohol
NaOH
HCl
Hot water

17. Solution
Amines are basic in nature. Therefore, aniline reacts with HCl to form a salt which dissolves in water.
Hence, aniline can be separated from benzene by using HCl.
Hence, answer is (c).

18. Distillation
Simple distillation- difference in boiling points of compounds is more than 40ºC. e.g.– chloroform (b. p. 334K) and aniline (b. p. 457K).

19. Distillation
(ii) Fractional distillation- difference in boiling points of compounds is less than 40ºC. e.g. – acetone (b. p. 329K) and methyl alcohol (b. p. 338K).

20. Distillation
(iii) Vacuum distillation- used for organic compounds which decompose at or below their boiling points. e.g. Glycerol.

21. Distillation (iv) Steam distillation- used for
organic compounds which are immiscible with water and are steam volatile e.g. Aniline.

22. Questions

23. Illustrative problem The most suitable method for the
separation of mixture of ortho and
para nitrophenol in the ratio of 1:1 is
distillation
crystallisation
vapourisation
colour spectrum

24. Solution
The boiling point of o-nitrophenol is 210oC and that of p-nitrophenol is 245oC.
Therefore, vapours of o-nitrophenol will be formed first (lower boiling point) and collected seperately and vapours of p-nitrophenol will be formed latter.
Hence, answer is (a).

25. Differential extraction
Used to extract pure organic compounds from their aqueous solution by shaking with organic solvent in which they are highly soluble.
Eg. Benzoic acid from its aqueous solution using benzene.

26. Chromatography Used to purify small samples.
Based on selective adsorption or partition between stationary and mobile phase.
Column Chromatography- based on adsorption, used for bulk quantities.
Thin layer Chromatography- based on adsorption, used for quantitative analysis.

27. Chromatography
Paper Chromatography- based on partition and used for quantitative and qualitative analysis.
Gas Chromatography- used to separate and analyse volatile organic liquids.
High performance liquids Chromatography (HPLC)- used for qualitative and quantitative analysis of organic compounds.

28. Criteria of purity of organic compounds
Boiling point.
Melting point.
Mixed melting point.

29. Qualitative analysis
Detection of C, H, N, halogens P, S, and oxygen.

30. Detection of carbon and hydrogen

31. Detection of carbon and hydrogen

32. Detection of nitrogen

33. Lassaigne’s extract Lassaigne’s extract is prepared to
convert covalency of organic compound into electrovalency by fusing with Na.

34. Organic compound Fe(CN)6 Na4 F e ( C N ) Organic compound3
Organic compound
Lassaignes’s extract
Fused with sodium
(Na)
(has NaCN)
sodium cyanide
Few drops of NaOH
and freshly prepared FeSO
Sodium ferrocyanide
Ferric ferrocyanide
prusslain blue
colouration confirms
presence of nitrogen
in organic compounds
Excess of HCl
and FeCl
(ferric chloride)

35. Detection of halogen

36. Lassaigne’s test for halogens

37. Detection of phosphorus

38. Detection of sulphur

39. Questions

40. Illustrative problem When acetic acid and lead acetate
solutions are added to sodium
extract, black percipitate is formed.
It shows that organic compound has
_____ element.
chlorine
oxygen
phosphorus
sulphur

41. Solution Sodium extract + CH3COOH + (CH3COO)2Pb Black ppt (PbS)
It shows the presence of sulphur in organic compound.
Hence, answer is (d).

42. Lassaigne’s test for Sulphur

43. Detection of oxygen
Presence of oxygen in organic compound is detected by testing for functional group containing oxygen eg- alcohol (–OH), aldehyde (–CHO), ketone (RCOR), carboxylic acid (–COOH), ester (–COOR) and nitro (–NO2).

44. Presented by A K Chabiri KVBalasore Thank you
Presented by A Chabiri
K V Balasore Thank you
Presented by A K Chabiri KVBalasore Thank you