LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 22

THIRD SEMESTER – NOV 2006

         CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

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

 

 

 

 

Part A

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

 

1. What is benzoin reaction?
2. Draw the Frontier Molecular Orbital interaction of 1,3-butadiene and ethylene under photochemical conditions.
3. How will you effect the following isomerisation? Write the mechanism.

 

4. Write the Woodward Hoffmann rules for electrocyclization reaction.
5. Explain the change in the geometry of excited state molecule in a photochemical process and the variation in its physical property.
6. What is Norrish type I and II cleavage reactions? Give suitable examples.
7. What are the important guidelines to be followed while choosing alternate synthetic route?
8. Explain the umpolung concept of synthesis with suitable example.
9. Explain the mechanism of the following reaction.

 

10. What are the products formed when benzene is subjected to Birch reduction?

 

Part B

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

 

11. Explain Michel addition reaction with an example.
12. Draw correlation diagram for the electrocyclization of 1,3,5-hexatriene for the dis-rotatory approach. State whether the reaction is feasible by thermal or photochemical means.
13. Predict the products in the following pericyclic reactions and explain the mechanism with proper stereochemistry.

 

 

 

 

 

 

 

 

14. Predict the mechanism of the following reaction.

 

15. Explain the mechanism of Paterno Buchii reaction. How does this take place in case of an alkyne?
16. Explain the mechanism of photochemical rearrangement of 4,4-diphenylcyclo- hexenone.
17. Describe a general scheme of synthesizing various mono functionalized compounds starting from alcohols.
18. Describe a suitable method to prepare the following compounds.

 

 

 

19. What is chemoselectivity? How well are chemoselective reactions performed? Explain with any two examples.
20. Explain the mechanism of electroorganic synthesis with an example.
21. How is cubane synthesized? Explain the mechanism.
22. Explain the mechanism of oxidation using
23. a) mercuric acetate and b) SeO₂.

 

Part C

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

 

23. a) Explain the mechanism of following reactions.
24. i) Hydroboration of carbonyls ii) Darzens reaction.
25. b) Predict the reaction mechanism of the following reaction.

 

 

 

24. a) Predict the product in the following sigmatropic rearrangement reactions.

 

 

 

1. b) Explain the effect of substituents on the cycloaddition reactions.

 

 

 

 

 

 

 

 

 

25. a) Predict the product and explain the mechanism of following reactions.

 

 

 

1. b) Derive Stern Volmer expression for photochemical quenching.
2. Explain the complete retrosynthetic analysis and subsequent synthesis of longifolene.
3. Explain the mechanism of following reactions.
4. a) Wolf Kishner reduction
5. b) Claisen-Schmidt reaction
6. c) Stobbe reaction with aromatic ketones
7. Explain the retrosynthetic analysis of the following compounds

 

 

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GH 38

LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2008

CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

 

Date : 26-04-08                  Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

Part – A

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

1. How hydroxyl groups are added on to carbon-carbon multiple bonds?
2. Draw the Frontier Molecular Orbital picture for the cycloaddition of 1,3-butadiene and ethylene.
3. Predict the product.
4. Give an example for 3,3-sigmatropic rearrangement and explain the mechanism.
5. State Stark Einstein and Grothus Draper laws of photochemistry.
6. What is Norrish type II reaction? Give an example.
7. How protective groups are important in the synthesis of an organic compound?
8. What are synthons? Identify suitable synthetic equivalents for the following synthons.

C₆H₅CH₂⁺, (CH₃)₂CH^¯

9. Write the mechanism of SeO₂ oxidation.
10. Why convergent synthesis is a better technique than stepwise synthesis?

 

Part – B

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

11. Explain the mechanism of NaBH₄ reductions with an example.
12. How regioselectivity is explained in cycloaddition reactions? Give suitable examples.
13. The following compound undergoes sigmatropic rearrangement reaction. Write the mechanism of the reaction and predict the product/s.

 

14. Predict the stereochemistry of the product and write the mechanism of the reaction.

 

15. Explain the Barton reaction in steroidal compounds.
16. How photoisomerisation takes place in alkene compounds? Explain with any two examples.
17. Write the retrosynthesis of the following compounds.
18. How are monofunctionalised compounds prepared from alkylhalides? Write a scheme to explain this.
19. What is electroorganic synthesis? Elaborate on electrooxidation reactions with suitable examples.
20. Discuss on C-C disconnections in 1,3- and 1,4-difunctionalised compounds with examples.
21. Write a short note on aldol and crossed aldol condensation reactions.
22. Bring out the differences between Clemmensen and Wolff Kishner reductions with suitable example.

Part – C

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

23. Write the mechanism of the following reactions and explain.
24. a) Knoevenagel reaction
25. b) Claisen-Schmidt reaction
26. c) Darzen’s reaction
27. How are the following compounds synthesized by retrosynthetic approach?

 

25. a) Write the photochemical rearrangement of 4,4-diphenylcyclohex-2-en-1-one with complete mechanism.
26. b) Explain various photochemical processes taking place in the excited state.
27. a) Explain the mechanism of Paterno Buchii reaction in alkenes.
28. b) Find out the products with proper stereochemistry in the following reactions.
29. Explain the mechanism of the following reactions.

 

 

28. a) Write the complete mechanism of synthesis of cubane.
29. b) Explain the chemoselectivity of the oxidizing agents with suitable examples.

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

DB 25

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – November 2008

    CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

 

Date : 03-11-08                   Dept. No.                                          Max. : 100 Marks

Time : 9:00 – 12:00

Part-A

Answer ALL questions.                                                                                                                                   (10 ´ 2 = 20)

1. What is Stobbe reaction?
2. Calculate the percentage yield of aspirin formed?

 

25 g                                                        22 g                                         20 g

3. Define umpolung concept. What are its advantages?
4. What is the thermal reaction between allylic anion and acrolein?
5. Draw the FMO picture for photochemical electrocyclization of 1,3,5-hexatriene.
6. What are cheletropic reactions? Give examples.
7. What is the stereochemistry of (1,5) sigmatropic rearranged product? Represent it with an FMO diagram.
8. Write the equation involving oxidation of organic compound using neutral KMnO₄ solution.
9. Define photoquenching. How does it take place?
10. What are hot ground state reactions?

 

Part-B

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

11. Identify the product and explain the mechanism of reaction.
12. Using alcohol, how are various monofunctionalised compounds synthesized?
13. Explain any five guidelines with example for the C-C disconnections.
14. How FGI plays an important role in the retro synthesis of an organic compound?
15. Explain the mechanism of LiAlH₄ reduction? What are the functional groups reduced by this reagent? Give an example.

 

16. Predict the product and explain the mechanism of following reactions.
17. Using electroorganic synthesis, how are the following compounds prepared?

 

 

 

18. Explain the mechanism of following reaction.
19. Write a short note on the effect of substituents on the cycloaddition reactions.
20. With atleast 5 degenerate structures being drawn, explain the degenerate sigmatropic rearrangement in the following compound.
21. Explain the photoreduction of benzophenone using
22. a) diphenylcarbinol b) 2-propanol
23. Predict the products in the following photochemical reactions with mechanism.

 

Part-C

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

23. Explain the mechanism of following reactions. (3 + 4 + 3)
24. a) Mannich reaction
25. b) Perkin reaction
26. c) Benzoin condensation.
27. Predict a suitable mechanism for the following reactions. (5 + 5)
28. a) Draw the correlation diagram for the cycloaddition reaction of 1,3-butadiene and ethylene. State whether the reaction is thermally or photochemically feasible. (6)
29. b) How chemoselective are the oxidizing agents? Explain this with suitable examples. (4)
30. a) Explain the synthesis of longifolene. (7)
31. b) How catalytic hydrogenation can control stereochemistry in alkynes? (3)
32. a) How regioselective reactions are converted into regiospecific with the help of controlling elements. Discuss with suitable examples.                                                                                                              (5)
33. b) Bring out a suitable retrosynthesis for the following target molecules. (5)
34. a) How does 4,4-diphenylcyclohexan-2,5-dienone undergo photochemical rearrangement. Give a detailed account of it.                                                                                                                         (7)
35. b) Explain the mechanism of Paterno Buchii reaction in alkynes. (3)

 

 

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   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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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – NOVEMBER 2010

    CH 3808  – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

 

Date : 29-10-10                 Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

Part-A

Answer ALL questions.                                                                                                                (10 ´ 2 = 20)

01     What are the merits of FGI? Give suitable examples.

02     How is mercuric acetate oxidation done?

03     How is Birch reduction regioselective? Give suitable examples.

04     What are cheletropic reactions? Give examples.

05     Write a short note on degenerate sigmatropic rearrangement reactions.

6. What are the advantages of using phosphoryl esters instead of phosphanes in Wittig reactions?
7. 30 g of toluene after various conversions forms 25 g of benzamide. What is the percentage yield of the reaction?

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

9. Represent various photophysical reactions using Jablonskii diagram.
10. What are hot ground state reactions? Give an example.

 

 

Part-B

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

11. How are primary and secondary amines prepared by Mannich reaction?
12. How regioselective compounds can be converted to regiospecific? Explain with suitable examples.
13. What are the various methods of C-C disconnections made during retrosynthetic analysis? Discuss any five in detail.
14. Perform retrosynthesis and subsequently report the synthesis of the given compound.
15. How is cubane synthesized?.
16. Explain the mechanism of catalytic reduction using metals?
17. Explain the mechanism of hydroboration and oxidation reaction
18. How are 5 and 7 membered heterocyclic compounds prepared by cycloaddition reactions?

 

 

19. Predict the products formed by the following reactions.
20. Draw correlation diagram for the electrocyclization reaction of 1,3-butadiene by dis-rotation. Predict whether the reaction is thermally or photochemically allowed.
21. What is Barton reaction? Predict the product from the following compound undergoing above reaction.
22. Predict the products in the following reactions.

 

 

 

Part-C

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

23. Explain the mechanism of following reactions.
24. a) Benzoin condensation
25. b) Stobbe reaction
26. c) Perkin reaction
27. a) What are Boc and Bn protecting groups? How are they involved in the protection of various functional groups?

 

 

1. b) Explain the retrosynthesis of the following compound.
2. a) How are unnatural synthons useful in the synthesis of difunctional compounds? Explain with examples.
3. b) How is longifolene synthesized?

26     a) Compare Wolf Kishner and LiAlH₄ reductions with examples.

1. b) How are active methylene compounds play significant role in organic synthesis? Explain the mechanism of Knoevenagal reaction.
2. a) Predict the stereochemistry of the products of the following reactions.
3. b) How cycloaddition is regioselective? Explain with any two examples.
4. a) Derive Stern-Volmer expression.
5. b) How does 4,4-diphenylcyclohex-2-en-1-one undergo photochemical rearrangement reactions? Write the complete reaction.

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – APRIL 2012

CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

Date : 21-04-2012             Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

Part-A

Answer ALL questions.                                                                                                          (10 ´ 2 = 20)

1. Write the mechanism of Mannich reaction.
2. Calculate the percentage yield of aspirin formed?

 

25 g                   20 g                 20 g                   20 g

3. Write a short note on the following terms.

Synthons, FGI and FGA

05     What are the advantages of electro organic synthesis?

4. How is Birch reduction done in toluene?
5. Draw the FMO orbital diagram of 1,3,5-hexatriene for thermal electrocyclization.
6. Why group transfer reactions are neither cycloaddition nor sigmatropic rearrangement reactions?

08     How will you effect the following conversion?

9. State the laws of photochemistry.
10. Write short notes on intermolecular energy transfer processes.

 

Part-B

Answer any EIGHT questions.                                                                                                  8 ´ 5 = 40)

11. Explain the benzoin condensation reaction and its mechanism. What is the order of the reaction with respect to the substrate? Why?
12. Explain any five types of C-C disconnections with examples.
13. What are protecting groups? How are carbonyl and carboxylic acid groups protected and deprotected?
14. Explain chemoselectivity and stereoselectivity. How can these be converted into “specificity” reactions?
15. Compare the nature of reduction reactions of LiAlH₄ with that of NaBH₄? (2 x 2½)
16. How catalytic hydrogenation can control stereochemistry in alkynes? Explain with any two examples.
17. Compare the KMnO₄ oxidations in acidic, basic and neutral conditions.
18. Draw the correlation diagram for the electrocyclization of 1,3-butadiene for disrotation.

19     a) State Woodward Hofmann rules for electrocyclization and cycloaddition reaction.

1. b) Identify the possible products in the following reaction.
2. Predict the products in the following reactions and explain the mechanism.
3. Write a short note on various photochemical processes taking place in the excited state.
4. Write the mechanism of photochemical rearrangement of 4,4-diphenyl-2-cyclohexenone.

 

Part-C

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

23. Write a short note on the following. (4 + 3 + 3)
24. a) Stobbe reaction
25. b) Wittig reaction
26. c) Darzen’s reaction
27. Perform retrosynthesis and subsequently synthesize the given compounds. (5 + 5)

 

25. a) Define Natural reactivity and Umpolung concept with examples. What is the importance of these concepts?    (4)
26. b) Explain the mechanism of Knoevenagal and Reformatsky reactions. (6)

 

26. a) Write the mechanism of following reaction (4).
27. b) Write the correlation diagram for the cycloaddition reaction of two ethylene molecules. State whether the reaction is thermally or photochemically feasible. (6)
28. a) How is norethisterone synthesized? (6)
29. b) Explain regioselectivity in cycloaddition reactions with examples. (4)
30. a) Explain the photoreduction of benzophenone using (6)
31. i) diphenylmethanol and ii) 2-propanol.
32. b) Write a short note on the photochemistry of a,b-unsaturated ketones. Give an example. (4)

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – NOVEMBER 2012

CH 3808 – PHOTOCHEMISTRY AND ORGANIC SYNTHESIS

 

 

Date : 01/11/2012            Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

Part-A

Answer ALL questions:                                                                                                         (10 ´ 2 = 20)

1. How is diborane specific in its reactivity towards substituted alkenes?
2. Draw the FMO picture of the excited state HOMO of 1,3,5-hexatriene.
3. What are regioselective reactions? Give an example.
4. What are the products formed when ethyl bromide is reduced electrochemically on platinum electrode?
5. Predict the stereochemistry of the product.
6. What is Fries photochemical rearrangement? Write the mechanism of the reaction.
7. What are the synthons prepared from the following synthetic equivalents?
8. a) 2-bromobutane b) acetyl chloride
9. What is the geometry of excited state ethylene molecule? Give reasons.
10. What are group transfer reactions? Give examples.
11. What is oxy-Cope rearrangement reaction? Give an example.

 

Part-B

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

11. Why Wittig Horner reaction is preferred to Wittig reaction? Mention the advantages of the Wittig Horner reaction with an example.
12. Explain the synthesis of following difunctionalised compounds.
13. a) 1,3-propanediamine b) ethyl acetoacetate
14. How are protection, activation and attachment of bridging group done repeatedly in the synthesis of a polypeptide?
15. Explain the mechanism of following reactions.
16. a) oxidation of an 2-butene by KMnO₄ in basic medium.
17. b) Wolff Kishner reduction of acetophenone
18. Write the complete mechanism of electroreduction of nitrobenzene.
19. Perform retrosynthetic analysis and suggest a suitable synthetic method of the following. (3 + 2)

 

17. Draw correlation diagram for the electrocyclization of 1,3-butadiene by con rotation. Predict whether the reaction is thermally or photochemically allowed.
18. If hydrazobenzene in acid medium undergoes (3,3)- and (3,5)-sigmatropic rearrangements, what are the products formed? Explain the mechanism of the reaction.

 

19. Explain the mechanism of the following reaction and predict the stereochemistry of the mentioned H atoms in the product.
20. What is Barton reaction? How does it take place in steroids? Explain with an example.
21. How does 4,4-diphenylcyclohex-2-en-1-one undergo Zimmerman rearrangement to form various photochemical products?
22. Explain the Norrish type-I and type-II reactions with an example each.

 

Part-C

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

23. a) Write the stereochemical importance of Stobbe reaction. (2)
24. b) Explain 1,2- and 1,4-Michael addition reactions. (5)
25. c) How unnatural synthons are used to prepare 1,2-difunctionalised compounds? Explain with an example. (3)
26. a) How are C-C disconnections done? Explain any four guidelines. (6)
27. b) Perform retrosynthetic analysis and suggest a suitable synthetic route to the following compound (4)
28. a) Explain protection and deprotection of an amine. (4)
29. b) Explain the mechanism of the following reactions with examples. (3+3)
30. i) NaBH₄ reduction of an imine ii) Peracid oxidation
31. a) Explain the synthesis of cubane. .           (5)
32. b) How mercuric acetate acts as a dehydrogenating agent? Explain with any two examples.                                                                                                    (5)
33. a) Predict a suitable mechanism for the following thermal reaction.            (4)
34. b) Discuss the FMO interactions in the 1,3-, and 1,5-sigmatropic rearrangement reactions. How is the stereochemistry altered in the product? (6)
35. a) Explain photoisomerisation reaction of stilbene. How is the process controlled by photosensitizers?                                                                            (6)
36. b) Explain the di-p-methane rearrangement reaction with an example. (4)

 

 

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