LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 18

THIRD SEMESTER – NOV 2006

                              CH 3800 – ORGANIC CHEMISTRY – III

 

 

Date & Time : 25-10-2006/9.00-12.00      Dept. No.                                                    Max. : 100 Marks

 

 

 

Part A

Answer ALL questions.                                                                       (10 ´ 2 = 20 marks)

1. Write a short note on [4+2]-cycloaddition in dipolar compounds.
2. What is a cheletropic reaction? Give an example.
3. What is Alder’s endo rule. Explain with an example.
4. Define the following. a) Photo quenching b) II law of photochemistry
5. Write a short note on the fate of the excited state molecules in a photochemical reaction.
6. Explain retro synthetic approach with an example.
7. What are annelation reactions? Give an example.
8. How would you plan the synthesis of 3-methyl-6-hepten-2-one by span technique?
9. Give a synthesis based on umpolung concept of seebach.
10. What are the importance of three component system in Clemmensen reduction?

 

 

Part B

Answer any EIGHT questions.                                                           (8 ´ 5 = 40 marks)

11. Draw a correlation diagram for the cycloaddition reaction of 1,3-butadiene and ethylene. State whether the reaction is thermally or photochemically feasible.
12. Predict the products in the following pericyclic reactions and explain the mechanism with proper stereochemistry.

 

 

13. Predict the mechanism of the following reaction.

 

14. Derive Stern Volmer expression for photochemical quenching.
15. Explain the photochemical rearrangement of 4,4-diphenylcyclohexenone.
16. What is Barton reaction? Explain its reaction mechanism in a steroidal compound.

 

 

 

17.    Explain the mechanism of Birch reduction. Identify the products obtained when the following are subjected to this reduction: (a) Benzoic acid and (b) Anisole.  Justify your answer.

18.    Explain the importance of electroorganic synthesis over the conventional synthesis in synthesizing bridged compounds with suitable examples.

19.    Explain the synthesis of reserpine.

20.    Explain the mechanism of Reformatsky reaction.  How is this reaction useful in organic synthesis?

21.    Oxymercuration-demercuration reactions follow Markownikov’s addition while Hydroboration-oxidation follows Anti-Markownikov’s addition. Why?  Explain with two suitable examples.

22.    What are stereospecific control elements?  How are they useful in organic  synthesis?

Part C

         Answer any FOUR questions.                                                   (4 ´ 10 = 40 marks)

23. Predict the reaction mechanism of the following reactions.

a)

 

b)

 

 

24. a) Predict the products of following reactions.

 

 

1. b) “Cycloaddition reactions are regioselective.” Explain with any two examples.

 

 

 

 

 

 

 

25. a) Photo reduction of benzophenone with diphenylmethanol involves a quantum     yield of 1 compared to that of 2-propanol with 2. Explain.
26. b) Explain the photochemical rearrangement of 4,4-diphenylcyclohexen-2,5-    dienone.
27. a) How would you synthesise Norethisterone?
28. b) What are the advantages of selenium dioxide oxidation? Explain the mechanism      with suitable examples.
29. a) Explain the steps involved in the synthesis of longifoline.
30. b) Identify the product in the following. Explain with mechanism.
    Me₂C=CH-CO-CH₃      A   +   B
31. Explain the following:
32. Perkin reaction is most widely used in the synthesis of coumarin.
33. Benzaldehyde is condensed with ketonic ester in retrograde aldol condensation reaction.
34. Alkylation of active methylene group is an important step in organic synthesis in increasing carbon skeleton.

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

LM 40

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2007

CH 3800 – ORGANIC CHEMISTRY – III

 

 

 

Date & Time: 24/04/2007 / 9:00 – 12:00      Dept. No.                                       Max. : 100 Marks

 

 

PART-A

Answer ALL questions.                                                                       (10 ´ 2 = 20 marks)

1. Effect the following conversion.

 

2. State Woodward Hofmann rules for electrocyclization reactions.
3. Predict the sigmatropic reactions in 1,5-systems with examples.
4. Define Norrish type II cleavage reactions. Give an example.
5. What is photosensitization? What is its importance?
6. ‘Convergent synthesis is a better method in organic synthesis than in stepwise synthesis’. Substantiate this statement with a suitable example.
7. What are fragmentation reactions? Give an example.
8. How would you plan the synthesis of 6-methyl-3-octen-2-one by span technique?
9. What is first generation asymmetric synthesis?
10. What are the importance of three component system in Clemmensen reduction?

 

 

 

PART-B

Answer any EIGHT questions.                                                           (8 ´ 5 = 40 marks)

11. Draw the correlation diagram for the electrocyclization of 1,3,5-hexatriene. Predict whether the reaction is feasible thermally or photochemically. (5)
12. Find out the products with proper stereochemistry in the following reactions.(2´2½)

 

 

 

 

 

13. Predict the products in the following sigmatropic reactions.

 

 

14. What are the products formed when 4,4-diphenylcyclohexen-2-one undergoes photochemical rearrangement. Write the mechanism of the reaction.
15. Illustrate with any two examples, the structure of a molecule in a photochemically excited state.
16. What is photoisomerisation? Explain with an example.
17. How would you plan the synthesis of 2-methyl-2-butene by disconnection approach? Explain.
18. ‘Symmetric target molecules can be planned by disconnection approach symmetrically’.

Explain this with a suitable example.

19. Explain the role of selectivity and specificity in organic synthesis by taking two examples for each.
20. How are the following conversions effected?
21. a) 2,3-dimethylcyclohex-2-en-one ¾¾®  2,2,3,3-tetramethylcyclohexanone
22. Isopropyl alcohol ¾¾® 1-phenyl-2-methyl-2-propanol
23. Explain the synthesis of 1,2-difunctionalised compounds with two suitable examples.
24. Elucidate the structure of reserpine by synthesis.

 

 

PART-C

Answer any FOUR questions.                                                            (4 ´ 10 = 40 marks)

23     a) How cycloaddition reactions are stereoselective? Illustrate with suitable examples.

1. b) Predict the stereochemistry of electrocyclisation in 4 and 6 electron systems. Give suitable examples.

24     a) Predict the mechanism of following reactions.

 

 

1. b) Derive the equation for Stern-Volmer expression.

 

 

 

 

 

 

25     a) Explain the Paterno Buchii reactions in alkenes and alkynes with examples.

1. b) Explain the following photochemical rearrangement reaction.

 

26. a) Establish the structure of longifolene by synthesis.
27. b) What are the synthetic importance of Reformatsky reaction? Explain with two suitable examples.

 

27. a) What are the synthons and synthetic equivalents in the synthesis of phenyl hydroxyl amine and benzanilide?
28. b) Explain the synthesis of norethisterone.

 

28. Explain the use of the following in the organic synthesis, with an example each. Explain the mechanism.

 

1. a) Diels-Alder reaction
   b)            Knoevenagel reaction
   c)            Perkin reaction
   d)            Electroorganic synthesis.

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

GH 53

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2008

    CH 3800 – ORGANIC CHEMISTRY – III

 

 

 

Date : 25/04/2008            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

PART-A

Answer ALL questions.                                                                       (10 ´ 2 = 20 marks)

1. What is group transfer reaction? Give an example.
2. State Woodward Hofmann rules for electrocyclization and cycloaddition reaction.
3. Give an example for 3, 3-sigmatropic rearrangement and explain the mechanism.
4. What are hot ground state reactions? Give an example.
5. Write a short note on photoisomerisation with an example.
6. What is retrosynthetic approach in organic synthesis? Give an example.
7. What are regiospecific reactions? Give an example.
8. What happens when phthalic anhydride is heated with acetic anhydride in the presence of sodium acetate?
9. What is the function of three layer solvent system in Clemmensen reduction?
10. How would you prepare bicyclic compounds using electroorganic synthesis?

 

PART-B

Answer any EIGHT questions.                                                           (8 ´ 5 = 40 marks)

 

11. Draw the correlation diagram for the cycloaddition reaction of 1,3-butadiene and ethylene. State whether the reaction is thermally or photochemically feasible.
12. Predict the products in the following sigmatropic reactions.

 

13. Explain regioselectivity in cycloaddition reactions with examples.
14. Explain the Barton reaction in steroidal compounds.
15. Discuss di-p-methane rearrangement with an example.
16. How photoreduction of benzophenone takes place by 2-propanol? Explain the mechanism of reaction.
17. Write a note on Birch reduction. What are the products obtained when benzoic acid and anisole are subjected to this birch reduction?  Explain the mechanism.
18. How is selenium dioxide used as an oxidizing agent? Explain with two examples and mechanism.
19. Explain the steps involved in the synthesis of cubane.
20. How would you plan the synthesis of the following compounds using span technique?
    a) 1-phenyl-1-pentanone
    b) 3-methyl-6-hepten-2-one
21. Identify the stereochemistry of product obtained in the hydroboration-oxidation reaction on unsymmetrical alkenes. How does this reaction differ from oxy-mercuration-demercuration reaction?
22. Explain the steps involved in the synthesis of norethisterone.

 

 

 

 

PART-C

Answer any FOUR questions.                                                            (4 ´ 10 = 40 marks)

 

23     a) Predict the mechanism of following reactions.

 

1. b) There are two rearrangements involved in the following reaction. Identify them and write the mechanism.
2. a) The following reaction involves two steps. Explain the mechanism of the reaction.
3. b) The following compound undergoes 5, 5-sigmatropic rearrangement reaction. Predict the product and write the mechanism of the reaction.

25     a) Write a short note on the photochemistry of a,b-unsaturated ketones with an example.

1. b) Explain the Paterno Buchii reactions in alkenes and alkynes with examples.
2. a) Explain the mechanism of Wittig reaction. How is this reaction useful in organic synthesis?
3. b) Establish the structure of reserpine by synthesis.
4. a) Explain the importance of Reformatsky reaction in organic synthesis.
5. b) What are stereospecific control elements? How are they useful in organic synthesis?
6. a) Explain the steps involved in the synthesis of longifoline.
7. b) ‘Alkylation of active methylene group is an important technique in increasing carbon chain in organic synthesis’ – Justify this statement with suitable examples.

 

 

 

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