LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

WD 22

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SIXTH SEMESTER – April 2009

       CH 6609 / 6603- SYNTHETICS ORGANIC CHEMISTRY AND SPECTROSCOPY

 

 

 

Date & Time: 25/04/2009 / 9:00 – 12:00     Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

Answer ALL questions:                                                                               (10 x 2 = 20)

1. What is retrosynthetic analysis in Organic chemistry.
2. What is disconnection approach.
3. Write the mechanism of C-alkylation of acetoacetic ester.
4. Write the product of aldol condensation of Acetaldehyde.
5. Predict the product of Diel’s – Alder reaction.

(i)                                                                            (ii)

 

 

6. Write the structure of the product

(i)                                                            (ii)

 

 

7. Calculate the max value for the following compounds using Woodward Fieser rule?

(i)                                                            (ii)

 

 

8. Concentrated solution of ethanol and 1, 2- glycol in CCl₄ exhibit broad O-H stretch near 3350 cm^-1 in their IR spectra. On dilution with CCl₄ the spectrum of 1, 2 – glycol does not change but that of ethanol exhibits a sharp band at 3600 cm^-1 in addition to the broad band at 3350 cm^-1. Explain the observation.
9. C¹³ is NMR active while C¹² is not explain.
10. How will you account for the appearance of prominent peaks at m/z 31, 42 and 70 in the mass spectrum of n- pentanol.

PART – B

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

11. Explain Umpolung synthesis.
12. What is the difference between conversion and synthesis.
13. Predict the product of Birch reduction of

• Benzoic acid (ii) Anisole.

14. Explain the product and mechanism of hydroboration of propene.
15. Write the mechanism and stereochemistry of Diel’s Alder reaction of

 

16. Discuss the method of protecting aldehyde and keto group?
17. Explain the importance of molecular in peak in mass spectra.
18. Write note on i) bathochromic shift      ii) coupling constants
19. How many different set of equivalent protons do each of the following compounds have? How many signals would each compound give in its ^lH NMR spectram
20. CH₃-CH₃ ii) CH₃-O-CH₃      iii) CH₃-CH₂–      -CH₂-CH₃                                iv) CH₃ –     -O CH₃
21. Give a brief account on Refrence standards used in ‘H NMR spectral technique.
22. The IR spectrum of methyl salicylate shows the following peaks at 3300 cm^-1 1700 cm^-1 3050 cm^-1, 1540 cm^-1, 1590 cm^-1 and 2950 cm^-1. Attribute these peaks to the following features of the molecule.
23. What is meant by shielding and Deshielding of protons in NMR spectoscopy.

PART – C

Answer any FOUR questions:                                                                     (4 x 10 = 40)

23. What are the application of Electrophilic Synthon and Synthetic equivalent in Retro Synthetic analysis.
24. i) How does IR spectroscopy useful to distinguish between  a) O-nitro phenol and p-

nitrophenol.

7. A compound having the molecular formula C₁₀H₁₄ exhibits following H^lNMR signals. d28(5H singlet) 0.880 (9 H S). Assign the structural formula of the compound.
8. i) How are the following groups protected and de protected during the synthesis of organic compound.
9. –NH₂ b) –OH group
10. An organic compound A (molecular formula C₉H₁₀O₂) exhibits the following spectral data

IR: 1745 cm^-1,             1225 cm^-1             749 cm^-1               697 cm^-1

UV: lmax 268, 264

^|HNMR=d1.96(3H, S)              5.00(2H, S)          7.22(5H, S)

26. i) How will you synthesis i) Acetylacetone               ii) Crotonic acid from ethylacetoacetate.

• “Diels-Alder reaction is highly stereo specific”. Explain.

27. Using Umpolung reaction how will you synthesis
28. C₆H₅-CH₂– -CH₃               ii)
29. Explain any two of the following (5+5)
30. Clemmenson reduction and its mechanism
31. Working principle of UV=Visible spectrophotometer with a block diagram.
32. Oxidation by peracids.

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SIXTH SEMESTER – APRIL 2012

CH 6609/CH 6603 – SYNTHETICS ORGANIC CHEMISTRY AND SPECTROSCOPY

 

 

 

Date : 23-04-2012              Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

PART – A

Answer all questions:                                                                                                       (10X2=20)

 

1. What do you mean by umpolung?
2. What are synthons? Give an example.
3. Complete the following reactions
4. Name the reagents used for the following conversion.

 

 

 

 

5. What is meant by an active methylene group? Give an example.
6. Give an important condition for a ketone to undergo Aldol condensation.
7. Calculate the λ_max for the following molecule:

 

 

8. How will you distinguish the following pair of isomers from their IR spectra?

 

 

9. Define the term chemical shift.
10. State nitrogen rule in mass spectra.

 

PART – B

Answer any EIGHT questions:                                                                                            (8×5=40)

 

11. Write a note on convergent synthesis.
12. Explain the various types of intermediates that are formed in organic reactions.
13. What are activating groups? Explain their usefulness in organic synthesis.
14. Write the mechanism of Wolf-Kishner reduction.
15. What is DIBAL? Explain its preparation and usefulness.
16. Write the mechanism of Aldol condensation.
17. Complete the following reactions

 

 

18. Explain the following with suitable examples:
19. a) Bathochromic Shift
20. b) Hyperchromic Shift
21. How is IR spectroscopy useful in detecting the H-bonding in organic compounds?
22. Explain the Proton NmR spectrum of ethyl alcohol contaminated with a little HCl.
23. Write the mechanism of McClafferty rearrangement with reference to mass spectroscopy.
24. Explain why cyclohexane gives only one peak at room temperature while it gives two peaks

at-100°C.

 

PART – C

Answer any FOUR questions:                                                                                        (4X10=40)

 

23. a) write a note on retrosynthetic analysis.   (5)
24. b) What are protecting groups? Explain the usefulness of them in organic synthesis.  (5)

 

24. Starting from acetoacetic ester, how will you prepare the following?

(i) Acetone (ii) succinic acid (iii) antipyrine   (iv) 4-methyl uracil (v) acetic acid.                  (10)

 

25. a) How will you distinguish the following pairs of compounds using IR Spectroscopy? (4)

(i) CH₃-CH₂-OH and CH₃-O-CH₃

(ii) maleic and fumaric acids

1. b) An organic compound of molecular formula C₉H₁₀O₂ showed three peaks in the PMR

spectrum as given below.

δ1.96 (S,3H)

δ5.0 (S,2H)

δ7.2 (S,5H)

Identify the structure of the compound.                                                                                   (6)

 

26. a) write a note on coupling constants.   (4)
27. b) A cyclic ketone (C₅H₈O, A) on reaction with NaOCH₃ gives a product B which has the

following NMR signals.

δ 3.6 (S,3H)

δ1.2 (S,9H)

Deduce the structures of A and B.                                                                                           (6)

 

27. Deduce the structure of the compound C₉H₈O which exhibited the following spectral data:

UV: λ _max(EtOH) : 285 nm (ε 45000)

IR: ۷_max (KBr) : 3090,2820,2750,1685,1630,1610,970 cm^-1

NMR: δ 6.62(1H, dd) J= 16 and 7 Hz, 7.41 (1H,d), 7.4 (5H, m), 9.66 (1H, d)

MS: m/z 132,131, 103, 91,77 and 51.

 

28. a) Discuss the instrumentation of IR Spectrometer with the block diagram. (6)
29. b) How are the following groups protected and deprotected during organic synthesis.  (4)

 

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