LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 39

THIRD SEMESTER – April 2009

CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

 

Date & Time: 16/04/2009 / 1:00 – 4:00         Dept. No.                                                       Max. : 100 Marks

 

 

PART-A

Answer ALL questions.                                                                                 (10 ´ 2 = 20)

1. What are the advantages of using phosphoryl esters instead of phosphanes in Wittig reactions?
2. 25 g of benzaldehyde after various reactions forms 20 g of benzamide. What is the percentage yield of reaction?

03     What is FGI? Give an example.

04     Differentiate homogeneous and heterogeneous catalytic reductions.

05     What are the advantages of electro organic synthesis?

06     Write the Woodward Hoffmann rules for cycloaddition reactions.

07     How will you effect the following conversion?

08     What is Alder’s endo rule? What is its effect on the stability of the products?

9. Represent various photophysical processes using Jablonskii diagram.
10. What is Norrish type II reaction? Give an example.

 

 

PART-B

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

11. Write the mechanism of Simmon-Smith reaction.
12. Carbonyl compounds have a key position in organic synthesis. Justify this statement.
13. How the following compounds can be disconnected to get suitable synthons?
14. a) b)

 

 

14. Perform retrosynthesis and subsequently synthesize the given compound.
15. Explain the effect of substituents on Birch reduction.
16. Compare in detail the Clemmensen and Birch reductions with examples.
17. How is electro organic oxidation performed? Explain with any two examples.
18. Explain the mechanism of following reactions.
19. a) Reformatsky reaction
20. b) Hydroboration reaction

 

 

 

19. How is degenerate sigmatropic rearrangement explained in the following compound?
20. Draw correlation diagram for the electrocyclization of 1,3-butadiene by con rotation. Predict whether the reaction is thermally or photochemically allowed.
21. What is Barton reaction? Predict the product in the following compound.
22. Explain the photochemistry of a,b-unsaturated compounds with atleast two examples.

 

PART-C

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

23. a) How Wittig Horner method is used to synthesize unsaturated compounds? Give suitable examples.
24. b) How protecting groups help suitably during FGI? Explain with an example.
25. a) How 1,2- and 1,3-difunctionalised compounds synthesized? Give one example for each.
26. b) Explain the retrosynthesis of the following compound.
27. a) How is cubane synthesized?
28. b) Explain the mechanism of mercuric acetate oxidation.
29. a) How NaBH₄ reduction is performed? Write the mechanism of reaction.
30. b) How active methylene compounds play significant role in organic synthesis? Explain the mechanism of Knoevenagal reaction.
31. a) Discuss the FMO interaction of following pericyclic reactions.
32. i) 1,5-sigmatropic rearrangement reaction
33. ii) thermal-6 electron-electrocyclization reaction
34. b) How cycloaddition is regioselective? Explain with any two examples.
35. a) What is photoisomerisation? How does it vary with respect to various photosensitizers used?
36. b) Derive Stern-Volmer expression.

 

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