LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 20

SIXTH SEMESTER – APRIL 2007

CH 6603 – SYNTHETICS ORG.CHEM. & ORG. SPECTROSCOPY

 

 

Date & Time: 23/04/2007 / 9:00 – 12:00   Dept. No.                                           Max. : 100 Marks

 

 

PART-A

Answer ALL questions.                                                                       (10 ´ 2 = 20 marks)

 

1. How H-bonding can affect the vibrational frequency of O-H group? Explain with suitable examples.
2. What is noise decoupling? What is its importance?
3. What types of magnetic nuclei are suitable to record NMR spectrum? Why?
4. Define bathochromic and hyperchromic shift.
5. What are the different types of mass spectrometric techniques?
6. Define functional group interconversion (FGI) with example.
7. Explain why 1,3-butadiyne (HCºC-CºCH) will not undergo Diels-Alder reaction with maleic anhydride?
8. How many moles of BH₃ are needed for the reduction of 9 moles of 1-butene?
9. Predict the product for the following reaction

 

10. What are synthons? Explain with examples.

 

 

PART-B

Answer any EIGHT questions.                                                           (8 ´ 5 = 40 marks)

 

11. List the types of vibrations occurring in the following compounds and mention the regions.
12. a) CH₃COCH₂CONH₂ b) CH₃CH₂COOH
13. What is the effect of solvents on the n ® p* and p ® p* transitions? Why does it occur?
14. Comment on the following.
15. a) vicinal coupling b) long range coupling         c) hetero atom coupling
16. Draw the schematic representation of 180° magnetic deflection mass spectrometer.
17. Calculate the number of splitting for the following compounds. Mention the chemical shift positions of each type of protons.
18. a) Ethyl methyl ketone b) ethylbutanoate

 

 

 

16. Predict the absorption maxima for the following compounds

 

17. Give the mechanism of chromate oxidation reaction of 1°, 2°, and 3° alcohols.
18. Predict suitable alkyne and catalyst for the synthesis of the following alkenes.
19. a) cis-2-pentene b) trans-2-butene
20. Explain the use of protecting groups in an organic synthesis with example.
21. Explain Swern oxidation with mechanism.
22. Explain Birch reduction with suitable example.
23. What is Diels-Alder reaction and explain the reactivity of diene and dienophile substituted with electron withdrawing and donating groups?

 

PART-C

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

 

23     a) What are the factors that affect fundamental vibrational frequencies? Explain.

1. b) Predict the proton nmr spectrum for the following compounds

 

24     a) What are lanthanide shift reagents? Give examples.

1. b) Calculate the molecular formula from the following mass spectral data.

m/e         15        29        42        43        45        60        61        62

Relative  21        16        12        100      94        58        1.4       0.26

25. a) Calculate the absorption maximum for the following compound. Predict its IR spectral pattern also.
26. b) From the following spectral data identify the compound and give reasons (molecular formula is C₆H₁₀O₂). (See Annexure)
27. Discuss the retrosynthetic analysis of the following compound and suggest suitable starting materials.
28. a) b)

 

 

 

27. How will you synthesize the following compounds starting from ethyl acetoacetate?
28. a) CH₃CH=CHCOOH b) CH₃COCH₂COCH₃               c) 4-methyl uracil
29. Predict the product and identify the name of the following reactions.

 

 

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