LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SECOND SEMESTER – APRIL 2011

CH 2504/CH 2502/CH 2500 – HYDROCARBONS AND STEREOCHEMISTRY

 

 

 

Date : 08-04-2011              Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

PART – A

Answer ALL the questions.                                                                                        (10 x 2 = 20 marks)

 

1. Prove that naphthalene is aromatic using Huckel’s rule.
2. Draw the structure corresponding to the following IUPAC name.

     Hex-3-ene-5-yne.

3. What happens when ethyl chloride is treated with sodium metal?
4. How does cyclopropane react with HI.

     Write the product formed.

5. What is saytzeff’s rule?
6. Write the products obtained when propyne reacts with NaNH₂.
7. Complete the following reactions.

       

 

8. Explain why phenol is nitrated more readily than benzene.
9. Assign E or Z configuration to each of the following compounds.
10.           ii.

                            

 

10. What is meant by 1,3 diaxial interaction in methyl cyclohexane?

 

PART – B

Answer any EIGHT questions                                                                                       (8 x 5 = 40 marks)

 

11. Explain why benzyl carbonium ion is more stable than ethyl carbonium ion.
12. What is Hybridization?Explain why four covalent bonds in methane are equivalent.
13. Explain the free radical mechanism of chlorination of methane.
14. What is meant by Anti Markonikov addition. Give its mechanism.
15. What is hydroboration?Explain with an example.
16. How will you synthesize 1,3 butadiene from 1-butene.
17. Discuss the molecular orbital structure of benzene.
18. Although chlorine atom is an electron withdrawing group,it is ortho-para directing

     group.  Explain.

 

 

 

19. Explain Haworth’s synthesis of Naphthalene.
20. Define geometrical isomerism.Describe any one method of distinguishing between cis and

      trans isomers.

21. Discuss the relative stabilities of chair and boat conformations of cyclohexane.
22. Explain Baeyer’s strain theory?Why is it not applicable to cyclohexane.

 

PART – C

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

 

23. a) Explain resonance with suitable examples.  (4)
24. b) Describe homolytic and heterolytic fission of a covalent bond.How carbonium ions,

          carbanions and free radicals are obtained.                                                                                 (6)

 

24. a) How will you synthesize cyclopentane using Dieckmann’s synthesis.       (4)
25. b) What is refining of petroleum?What different fractions are obtained on refining. (6)
26. Predict the products of the following reactions.   (10)                                                              

                 

             

 

26. a) Write a note on “stability of conjugated dienes”. (5)
27. b) Explain the mechanism of Nitration of benzene.       (5)
28. a) Explain Diel’s Alder reaction using suitable examples.       (4)
29. b) Predict the products of the following reactions.                                                                       (6)

 

       

 

28. Explain the various conformations of n-butane and discuss their stabilities based on the

      energy diagram.                                                                                                                                (10)

 

 

 

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