organic pg

1. APRIL 2016 55701/MCR1A
Time : Three hours Maximum : 75 marks
PART A — (10  1 = 10 marks)
Answer any TEN questions, each in 50 words.
1. Define prochrality.
2. Designate E/Z notation for the following
compound.
3. What are atropisomers?
4. Draw the structure of most stable conformation of
1,2 – dichloroethane.
5. Cis-decalin is a non resolvable recemate – why?
6. How – NO2 behaves as an ambident nucleophile?

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7. What is the reagent in Von-Brawn reaction?
8. Write Taft equation.
9. Explain primary isotopic effect with an example.
10. Nitrobenzene is less reactive than benzene
towards electrophilic substitution. Account.
11. What are the reagents used in Gattermann
reaction?
12. Which among the following is m-directing group?
3
3
3
2 OCH
,
)
(CH
N
Cl,
OH,
,
NH 




.
PART B — (5 × 5 = 25 marks)
Answer any FIVE questions, each in 200 words.
13. Draw the geometrical isomers of 1, 4 – dimethyl
cyclobutane and discuss their optical activity.
14. Illustrate enantiotopic and diastereotopic
hydrogens with suitable examples.
15. Discuss the stabilities of cis-and trans-9-methyl
decalin.
16. Write an account of nucleophilic substitution at
carbonyl carbon.

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17. How the following conversions are carried out?
(a)
(b)
18. Discuss the electrophilic substitution in
Pyridine-N-Oxide.
19. Discuss the mechanism of Reimer-Tiemen
reaction.
PART C — (4 × 10 = 40 marks)
Answer any FOUR questions, each in 500 words.
20. Discuss stereospecific and stereoselective reactions
with suitable examples.
21. Write an account of the following
(a) Cram’s rule.
(b) Optical isomerism in allenes.
22. (a) Discuss the stability and optical activity of
cis-and trans –1, 3 –dimethyl cyclohexane.
(b) Discuss the effect of conformation on the
oxidation of cyclohexanol.

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23. (a) Illustrate stereochemistry involved in SN1
and SN2 mechanisms with suitable reactions.
(b) Give the mechanism and synthetic utility of
Dickmann condensation.
24. Discuss any two non-kinetic methods of
determination of reaction mechanism with
suitable examples.
25. Write an account of the following :
(a) Mechanism of nitration in aniline.
(b) Gattermann reaction.
(c) Mechanism of nitration in pyrrole.
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