LOYOLA COLLEGE (AUTONOMOUS) CHENNAI – 600 034

B.Sc., DEGREE EXAMINATION – CHEMISTRY

SIXTH SEMESTER – APRIL 2011

CH 6609/6603 – SYTHETICS ORGANIC CHEMISTRY AND SPECTROSCOPY

DATE:11-04-2011                                                                                                                              MAX:100 MARKS

TIME:1:00 – 4.00

 

PART A

Answer ALL Questions                                                                                                                                  (10 x 2 = 20)

1. What are activating groups? Give
2. Suggest any two criteria for choosing protective groups?
3. Complete the following reactions

O

1.                                          H₂

Pd / C

 

1.   COOH

Na

Liq. NH₃

4. Mention the role of DMSO in oxidation reactions
5. What is the structure of aldol product from propanal?
6. What is the significance of active methylene group?
7. Calculate the l_max for the following

 

 

O

1. C – CH₃

 

8. The l_max of benzene is 256nm whereas aniline is 280nm – Give reason.
9. Predict the structural formula for the compound with the following molecular formula showing only one NMR signal a) C₂H₆O b) C₅H₁₂
10. Define nitrogen rule. Give an example.

 

 

 

 

PART B

Answer any EIGHT Questions                                                                                                                    (8 x 5 = 40)

11. Explain Retrosynthetic analysis.
12. What do you understand by linear and convergent synthesis? Explain.
13. Discuss synthon approach in construction reactions.
14. Discuss the mechanism of Clemmenson reduction and mention its significance.
15. Explain hydroboration reaction and mention the utility of the rection.
16. Explain Diels Alder reaction. Give any two examples.
17. Complete the following reaction

O

+ C₆H₅CHO                NaOH

 

CHO

 

 

1. NaBH₄

 

OCH₃                                    CH₃OH

                                                           

1. B₂H₆
2. CH₃ – (CH₂)₇ – CH = CH₂
3. H₂O₂
4. What are chromophores and auxochrome? Give examples.
5. Discuss the factors which affect the IR absorption frequency of a functional group.
6. Define chemical shift. Why is TMS a good reference standard in NMR spectroscopy.
7. How will you distinguish 2-pentanone and 3-pentanone using mass spectroscopy.
8. Explain shielding and deshielding mechanism.

 

PART C

Answer any FOUR Questions                                                                                                                     (4 x 10 = 40)

23. a) Explain umpolung synthesis.                                                 (5)
24. b) Using umpolung synthesis convert the following reaction.                                 (5)

O                                                                  O

nC₅H₁₁ – C – H                                               C₅H₁₁ – C – CH₂ – R

24. a) How will you distinguish the following pairs using IR spectroscopy.                                 (6)
25. CH₃ – CO – CH₃ and CH₃ – CH = CH – CH₂OH
26. O-hydroxy benzaldehyde and m- hydroxy benzaldehyde
27. b) Draw the structure of each of the following compounds which meets the given requirements in the NMR spectrum.                                 (4)
28. C₃H₃Cl₅ (one doublet and one triplet) ii. C₃H₇Cl (one doublet and one septet)
29. a) Explain spin-spin spliting with a suitable example.                                 (6)
30. b) A compound with molecular formula C₈H₈O gives the following NMR spectrum – multiplet
    d28 (5H), Doublet d 2.88 (2H), Triplet d 9.87 (1H). Determine its structure (4)
31. Using malonic ester how will you synthesis the following.
32. Succinic acid           Adipic acid
33. Cinnamaldehyde             n-Valeric acid.

• Barbituric acid.

27. a) An organic compound with molecular weight 72 absorbs at 274 nm.

In IR the bands are formed at 1715 cm^-1 (s), 2941 – 2857 cm^-1(m) and 1460 cm^-1 (m).

In NMR the signals  formed are 2.48 d quartet (2H), 2.12 d singlet (3H), 1.07 d triplet (3H). Determine the structure of the compound.

b)Define the following terms and mention its significance                                                            (4)

1. Base Peak ii. Metastable peak
2. a) Discuss the instrumentation of UV –Visible spectrophotometer with the block diagram.(6)
3. b) How are the following groups protected and deprotected during organic synthesis (4)                        – NH₂                 ii.             C = O                     iii.  – OH                iv.  –  COOH

 

 

Latest Govt Job & Exam Updates:

View Full List ...