LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 18

SIXTH SEMESTER – APRIL 2006

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

(Also equivalent to CHE 603)

 

 

Date & Time : 26-04-2006/9.00-12.00         Dept. No.                                                       Max. : 100 Marks

 

 

PART – A

                                                Answer all the questions                   (10 ×2 = 20 marks)

1. What are protecting groups? Give an example of a protecting group for amines and alcohols.
2. What is raney nickel and Adam’s catalyst?
3. Distinguish between linear and convergent method of synthesis.
4. Predict the product and reason for the formation of the product.
5. Add the necessary reagents for the forward and reverse reactions.
6. Identify the base peak when acetone undergoes fragmentation during mass spectral study.
7. Define hyperchromic shift. How does it arise in the electronic spectrum of an organic compound?
8. Name the methods by which non-first order NMR spectrum is resolved into a first order spectrum.
9. Calculate the frequency regions for N=O stretching vibrations.
10. Define the following a) auxochromes         b)  shielding effect

 

PART – B

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

11. How are the following conversions effected?
12. Predict which of the following products would be got in Baeyer-Villiger oxidation of cyclohexylmethyl ketone.Why?

 

13. Give the reterosynthesis and the synthesis of 2-aminocyclohexanone using umpolung concepts.
14. Give the reterosynthesis and the synthesis of the following.
15. Explain a) Aldol condensation b) Michael addition reaction
16. What are the diene and the dienophile used in the synthesis of the following compounds?
17. What is solvent cut-off region? How do solvents affect the lmax of any compound? Explain with suitable examples.
18. Write the various fragmentation pattern for an arbitrary compound A–B-C–D.
19. What are the advantages of FT-IR over dispersive IR spectrophotometer? Give suitable evidences to mark the differences.
20. Assign the IR spectral regions and calculate lmax of the following compound

 

21. What are the factors that affect the coupling constants of NMR signals? Explain any three in detail.
22. Explain the following with respect to ¹³C-NMR spectroscopy
23. a) Deuterium coupling b) nuclear overhauser effect

PART – C

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

23. Predict the product with mechanism
24. Give the reterosynthesis and the synthesis of the following
25. a) Predict the product with mechanism for the reaction of EAA with traces of
    sodium hydrogen carbonate.
    b) How are the following conversions effected?
26. a) Predict the number of NMR signals with increasing order of d values for each of the following compounds.
27. i) phenylacetic acid
28. ii) o-hydroxyacetophenone
29. b) Of the given pairs of isomers which will show the longest wavelength of UV absorption. Give reasons.
30. i) 1,2-pentadiene and 1,3-pentadiene
31. ii) 4-hept-1-enone and 4-hept-2-enone
32. For the given compound predict the following
33. a) IR vibrational frequencies for various groups present
34. b) Mass spectral fragmentation pattern
35. c) Proton NMR spectral data with splitting and chemical shift values.

CH₃-CH(CH₃)-CH₂-COOH

28. Elucidate the structure of the given organic compound from the following spectral data (Annexure-I). The molecular formula of the compound is C₆H₁₀O₂

 

 

 

 

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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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GH 23

LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SIXTH SEMESTER – APRIL 2008

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

 

 

 

Date : 25/04/2008                Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

PART – A

                                                Answer all the questions.                                          (10  ´  2   = 20)

 

1. What is the range of Infrared radiations ?What are the units used in IR spectroscopy.
2. What is chemical shift ?Why do we choose Tetra methyl silane (TMS) as a standard substance for recording chemical shift values.
3. How many NMR signals would you expect from the following compounds i.Toluene   ii.Allyl alcohol.
4. How will you use the UV- Visible spectral data to distinguish between the following pairs –  Ethyl benzene  and Styrene.
5. What is Nitrogen rule with respect to mass spectroscopy.
6. How will you convert diethyl malonate to butanoic acid?
7. Complete the following reactions.

 

8. Name the reagents A and B used to effect the following conversions.
9. i) CH₃-CH=CH-CHO   CH₃-CH=CH-CH₂OH

 

9. Complete the following reactions.
10. i) R₂CHOH     ?
11. ii) CH₃-CH₂-CO-CH₂-CH₂-CH₃  ?
12. Explain functional group inter conversion with an example.

PART – B

Answer any Eight questions                         (8  ´  5  = 40)

 

11. The Infrared spectrum of methyl salicylate shows the following peaks at 3300 cm^-1 , 1700 cm^-1, 3050 cm^-1, 1540cm^-1, 1590 cm^-1 and 2950 cm^-1 Attribute these peaks to the following features of the molecule.

(i) – CH₃   (ii)  C = O    (iii)  – OH group on the ring   (iv) Aromatic ring.

 

12. Write sort notes on a. bathochromic shift

b.Hypsochromic shift

1. Hyper chromic shift

 

13. What is meant by shielding and deshielding of protons in NMR spectroscopy.
14. What is mass spectroscopy ? What is the principle of mass spectroscopy.

 

15. The mass spectrum of 2- pentene shows m/e peaks at 70 , 55, 41, 29 and 27. Write down the different fragments and correlate their m/e values with the m/e peaks obtained.

 

16. Calculate the λ _max values for the following compounds . Give reasons for your interpretations.
17. Discuss any two methods that are commonly used for protection of alcoholic – OH group during synthesis of a organic compound.

 

18. How will you synthesize acetophenone using umpolung reaction.

 

19. Describe the use of chromic acid in the oxidation of alcohols and ketones. Write the mechanism involved.

 

20. How is NaBH₄ prepared ? Write any three synthetic applications of NaBH₄.

 

21. What is hydroboration ? Write the reagents and the mechanism involved in the reaction which converts propene to 1– propanol.

 

22. For the Diels Alder reaction predict the major product.

 

PART – C

     Answer any four questions.                    ( 4 ´ 10 = 40 )

23. i). Which one of the following compounds is most consistent with the IR spectrum given in the following figure.? Give reasons for your interpretation. C₆ H₅ – OH ,  C₆H₅ – COCH₃ , C₆H₅ – COOH , C₆H₅ –CH₂OH.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ii). Describe the appearance of the proton NMR spectrum of each of the following compounds. How many signals would you expect to find and how many peaks will each signal be split.

(a) Cl CH₂ – O – CH₂ CH₃        (b) 1,2-dichloroethane             (c) p-diethyl benzene.

 

24. i)How does Infrared spectroscopy useful to distinguish between inter molecular H-bonding and intramolecular H-bonding ? Explain using suitable examples.

 

102. ii) A hydrocarbon shows a mass parent peak at m/e 102. It exhibits NMR signals δ 7.4           (5 H ,Singlet) and δ 3.08 (1H Singlet). What is the probable structure of the hydrocarbon?

 

25. i) Describe the working principle of a UV–Visible spectrophotometer using a simple block diagram .

ii)Account for the splitting of PMR signals.

 

26. i) Explain the term umpolung with an example.

 

1. ii) Using 1,3 dithianes , how will you effect the following conversions.
2. benzaldehyde to C₆H₅ CH₂CH₂ C₆H₅
3. formaldehyde to C₆H₅ CH₂CH₂CH₂CH₂

 

27. i) How are the following groups protected and deprotected during synthesis of organic compounds.

(a)  –  NH₂ gp.             (b) – CHO gp.

1. ii) Complete the following reactions

(a)  CH₃-CH₂-CHO   +   CH₃-NH-CH₃   ¾®  ?

(b)

 

28. i) How will you synthesize

(a) Succinic acid

(b) Crotonic acid

from ethylacetoacetate

 

1. Diels Alder reaction is highly stereo specific – Account.

 

 

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