LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 4

SECOND SEMESTER – APRIL 2006

                                                     CH 2500 – ORGANIC CHEMISTRY – I

(Also equivalent to CHE 502)

 

 

Date & Time : 24-04-2006/1.00-4.00 P.M.   Dept. No.                                                       Max. : 100 Marks

PART – A

                                                Answer all questions                         (10 ×2 = 20 marks)

1. Draw the sawhorse and Newman projection structures of propane.
2. Arrange the following in the increasing order of stability.
   1, 3-butadiene, 1, 2-butadiene, 1, 4-butadiene.
3. Draw the structure of
   (a) (Z)-3-isopropyl-2-heptene (b) (E)-1-bromo-2-chloropropene.
4. Define the following (a) racemic mixture (b) resolution.
5. Arrange the following in the increasing order of reactivity towards Diel’s-Alder reaction.
6. What are the factors that affect the free radical halogenation of alkanes?
7. What is Baeyer’s test?
8. What happens when calcium carbide is treated with water?
9. What is Wurtz reaction?
10. Draw the structure of the following compounds
11. a) 2,6-dimethyl-4-ethyl-2,4-heptadiene
12. b) 3,5-diethyl-1,7-octadiyne.

PART – B

                                                Answer any eight questions             (8 × 5 = 40 marks)

11. What are conformers? How are they different from configuraitonal isomers? Give an example.
12. Predict the product with mechanism for the reaction of 2, 4-hexadiene with HCl.
13. The specific rotation of R-(+)-glyceraldehyde is + 8.7°. If the observed rotation of a mixture of R-glyceraldehyde and s-glyceraldehyde is +1.4°, what percent of glyceraldehydes is present as the R enantiomer?
14. Draw the various stereoisomers of 3-chloro-2-butne and indicate which of them are entantiomers and diastereomers.
15. Predict the product with mechanism
16. Define the following
    a) asymmetric synthesis b) chemoselectivity c) regioselectivity.
17. Compare the free radical chlorination and bromination of methane for reactivity and quantum yield.
18. Why the alternative mechanism of chlorination of methane is not possible? Explain with proof.
19. What is Kolbe’s synthesis? How is butane synthesized by above method?
20. How is ozonolysis used to differentiate 1-butene and isobutene. Write the mechanism of the above reaction.
21. What are the products formed when 1-butyne is subjected to hydroboration and oxidation. Explain the mechanism of the reaction.
22. Give the mechanism of addition of bromine to ethylene.

PART – C

                                                Answer any four questions   (4 × 10 = 40 marks)

23. Indicate whether the following pairs of compounds are identical or enantiomers or constitutional isomers.
24. Perform a conformational analysis of rotation of C2-C3 bonds in n-butane and explain using a potential energy diagram.
25. a) Dienes undergo free radical reactions faster than alkenes. Why?
    b) What are atropisomers? Give suitable example.
    c) Which of the following conjugated dienes would not react with a dienophile in
    Diel’s-Alder reaction? Why?
26. Explain in detail the chlorination reaction of methane. How many products are formed? Discuss the rate of the reaction and the reaction mechanism of the reaction.
27. a) A hydrocarbon reacts with conc. H₂SO₄ to form an alkyl hydrogen sulphates which on hydrolysis yields tert-butyl alcohol. What is the structural formula of the hydrocarbon? Write the equations.
28. b) Write the structure of the alkene, which on ozonolysis gives 2-butananone and 2-mehtylpropanaldehyde. Write the mechanism of the reactions.
29. a) compound A, C₄H₆ gave the following tests
30. i) A + Br₂ / CCl₄ ® B (C₄H₆Br₄)
31. ii) A + H₂ / Pt® C (C₄H₁₀)

Identify A, B and C

1. b) What are the uses of the following compounds?
2. i) ethylene ii) acetylene iii) propene

 

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