Anna Univ Paper - III : ORGANIC CHEMISTRY M.Sc May 2006 Question Paper

Anna University Chennai
Course: M.Sc. (CHEMISTRY) (Previous) DEGREE EXAMINATION
Year of the exam paper: MAY 2006
Subject => Paper - III : ORGANIC CHEMISTRY
Time: Three hours
Maximum : 100 Marks

PART - A - (4 x 10 = 40 marks)
Answer any FOUR questions

1. Explain the concept of aromaticity, anti-aromaticity and homo aromaticity with examples.

2. Write notes on:
(a) Hyper conjugation
(b) Tautomerism

3. Write an account of classical and non-classical carbocations.

4. Write notes on:
(a) Isotope effects
(b) Nitrenes.

5. What are free radicals? Mention their stability and reactivity.

6. Write notes on:
(a) Hydroboration
(b) Hunsdiecker reaction.

7. Outline the mechanism of Benzoin and stobbe reactions.

8. What is ElcB reaction? What are the requirements for the ElcB path? Give mechanism.

PART - B - (4 x 15 = 60 marks)
Answer ALL Questions

9. (a) Explain the terms .Localised. and .Delocalised. covalent bonds with examples. (8)
(b) Draw the different conformations of cyclohexane and explain their stability with energy level diagram. (9)

Or

(c) Write notes on:
(i) Resonance and
(ii) Fullerences (7)

(d) Explain Stereo selective and Stereospecific synthesis with suitable examples. (8)

10. (a) Explain the terms kinetic control and thermodynamic control with examples. (7)
(b) What are carbenes? Explain their reactivity with examples. (8)

Or

(c) Discuss SN1 and SN2 reactions with suitable examples. (8)
(d) Discuss the nucleophilic substitution in an allylic and vinylic system. (7)

11. (a) Explain the regio and chemoselectivity and orientation aspects in addition reactions of olefins involving electrophiles. (15)

Or

(b) Write notes on:
(i) Sandmeyer reaction (5)
(ii) Allylic halogenation (5)
(iii) Gattermann-koch reaction (5)

12. (a) Give a detailed account on E1 and E2 mechanisms in elimination reactions (15)

(b) Write short notes on:
(i) Witting reaction (5)
(ii) Mannich reaction (5)
(iii) Perkin reaction (5)

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