Anna University Chennai 2006 M.Sc Chemistry ORGANIC - Question Paper

M.Sc. (CHEMISTRY) (Previous) DEGREE exam :: MAY 2006
Paper - III : ORGANIC CHEMISTRY

Time: 3 hours Maximum : 100 Marks

PART - A - (4 X 10 = 40 marks)
ans any 4 ques.

1. discuss 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. elaborate 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? elaborate the requirements for the ElcB path? provide mechanism.

PART - B - (4 X 15 = 60 marks)
ans ALL ques.

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

Or

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

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

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

Or

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

11. (a) discuss 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) provide 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)

Earning:   Approval pending.