LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 54

FOURTH SEMESTER – APRIL 2007

CH 4809 – APPLICATIONS OF SPECTROSCOPY

 

 

 

Date & Time: 20/04/2007 / 9:00 – 12:00          Dept. No.                                                          Max. : 100 Marks

 

 

Part-A

                                                     Answer ALL questions.                                (10 ´ 2 = 20)

1. How would you distinguish the following using UV spectroscopy?
2. What are blue and red shifts? Give an example for each.
3. How would you explain the deshielding of alkenyl and aldehydic protons in organic compounds?
4. Find the equivalent and non-equivalent protons in the different conformers of
   (i) 1,2,3-tribromocyclopropane and (ii) 1,2-dibromocyclopropane.
5. What are the characteristics of fragmentation pattern for alkenes?
6. How is Raman spectroscopy useful in combination with IR to decide geometry of a molelcule?
7. Write a note on sources of IR radiation in an IR spectrophotometer.
8. What is reduced mass? Give its significance.
9. How does fine spectrum of esr arise?
10. What are prolate and oblate orientations?

 

Part-B

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

11. The following triene on partial hydrogenation gives three products, which are separated by GLC. How would you distinguish the products using UV spectroscopy?
12. How would you distinguish the following compounds using UV spectroscopy?

 

 

 

13. Draw the proton NMR spectrum of 2-bromo-4-nitrotoluene and explain different splitting patterns.

 

14. Establish the structure of the organic compound from the following NMR spectral data:
15. a) MF: C₉H₁₀ Signals: d04 quin(2H); d 2.91 t(4H); d 7.17 s(4H)
16. b) MF: C₁₀H₁₂ Signals: d65 m(2H); d 0.81 m(2H); d 1.37 s(3H); d 7.17 s(5H)

 

15. Depict the mass spectrum and explain the fragmentation pattern in
    (i) 2-methyl-1-pentene and      (ii) 2-hexanol.

 

16. Name and explain any three factors affecting the fragmentation of a molecule with suitable examples.

 

17. How does hydrogen bond affect IR spectrum of a molecule?
18. Why does cyclohexane show different IR spectra when temperature is changed?
19. What is Lande’s splitting factor in esr? Why does it remain constant for electron in any environment?

 

20. Account for the fact that esr is recorded at low temperatures and in solid state only.
21. Draw rough sketch of esr spectra of the following and explain the same (i) ¹²H₃

and  (ii) ¹³D  [I values for C¹² = 0;  C¹³ = ± ½ ;   H¹ = ± ½;    D² = ± 1]

 

22. How is the principle of NQR different from that of esr?

Part-C

                                                     Answer any FOUR questions                      (4 ´ 10 = 40)

23. On the basis of Woodward rules, calculate the expected position of the absorption

maximum in the following:

 

24. Explain the following with suitable examples:
    1. Spin decoupling
    2. Chemical shift

• Long range coupling

1. Base peak in mass spectrum
2. Internal standard in NMR

 

25. a) A compound, C₉H₁₀O₂, shows a molecular ion at m/e = 150 and a base peak at
    m/e = 135. Its infrared spectrum shows a strong band at 1680 cm^‑1. Its proton NMR shows signals in three distinct regions at d 2.3(3H, s), d 3.6(3H, s) and at d 7.1(4H, a pair of doublets).  Assign a structure for this compound.
26. b) How would you distinguish between (i) the isomeric alcohols 3-methyl-1-butanol and 2-methyl-2-butanol and (ii) 2-butanone and butyraldehyde using mass spectroscopy?
27. a) Discuss sample handling in IR spectroscopy.
28. b) Giving reasons, explain group frequencies of carbonyl group in (i) aldehydes;
    (ii) ketones; (iii) acyl halides and  (iv) carboxylic acids.
29. Explain the FT technology. Describe working of a FT – IR spectrophotometer and its advantage over a conventional IR spectrophotometer.
30. Discuss the applications of NQR spectral technique.

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

GH 46

FOURTH SEMESTER – APRIL 2008

CH 4809 – APPLICATIONS OF SPECTROSCOPY

 

 

 

Date : 23/04/2008            Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

PART A

Answer the following:                                                                     10 x 2 = 20 marks

1. Illustrate metastable ion peak with an example.
2. What is isobestic point?
3. Which of the following compound will show higher carbonyl stretching frequency? Give reason.
4. A hydrocarbon, C₅H_12, gives two signals at upfield in its proton decoupled CMR spectrum. How many signals shall be obtained in the high resolution PMR spectrum of the compound?
5. How many signals are expected in the ESR spectrum of naphthalene anion radical?
6. What are the selection rules for Raman Spectroscopy and ir spectroscopy?
7. What are the types of excitations observed in a molecule using (i)γ-rays (ii)X-rays?
8. Explain Frank-Condon principle.
9. State and explain Beer-Lambert’s law and its significance.
10. Give reasons (any two) for the unexpected high intensity of ligand field bands?

 

PART B

 Answer any EIGHT of the following:                                           8 x 5 = 40 marks

 

11. Using Woodward- Fieser Rules calculate λ_max (in nm) of the following compounds:
12. Discuss the use of ir spectroscopy in the study of hydrogen bond.
13. What are shift reagents? Cite two examples. How are they useful in PMR spectroscopy?
14. Explain various factors which influence the fragmentation pattern in mass spectroscopy.
15. What is meant by hyperfine splitting? Illustrate the same with ESR spectrum of methyl radical.
16. From the provided data of a compound, deduce its structure:

Molecular formula:  C₈H₈O₂

IR, ν, cm^-1 (important bands only): 3000- 2500(broad); 1710(s).

¹H NMR,  δ, ppm:   7.2(5H, s); 11.6(1H, s); 3.5(2H, s)

17. What are tetragonal distortions?
18. How does geometry of a molecule influence rates of substitution reactions of coordination compounds?                                                      
19. Why does KMnO₄ have high intense colour, while Mn(II) complexes show feeble colour?
20. Account for a shoulder observed in the electronic spectrum of [Ti(H₂O)₆]³⁺, despite it has d¹ configuration
21. Explain the principle of NQR spectroscopy.
22. Explain sample handling in ir spectroscopy.

PART C

 Answer any FOUR of the following:                                               4 x 10 = 40 marks

23. a) How are π _→ π* and n _→ π* transitions differentiated by solvent effects in UV spectroscopy? Explain with energy level diagram.
24. b) Discuss the principle of EPR spectroscopy.
25. Write notes on (a) McLafferty rearrangement (b) Stevenson’s Rule.
26. An organic compound has molecular formula C₁₀H₁₃NO₂, and its significant spectral features are as follows:

UV, λ_max (EtOH): K- Band appears at 290nm

IR,   ν  cm^-1 :   3402(s); 3318(s); 3025(s); 1695(s); 1580(s); 1580(m)

¹HNMR, δ, ppm:7.9(2H,d);6.7(2H,d); 4.75(1H,septet); 4.2(2H, broad); 1.25(6H,d)

Assign suitable structure to the compound and account for the spectral data.

26. Give a detailed account of CT and LF bands of coordination compounds and their usefulness.
27. Explain term symbols, taking d¹ electronic configuration as example. Also show how the terms get split in the presence of ligand field using Orgel and Tanabe-Sugano diagrams. Compare the properties of these diagrams and applications
28. Explain the use of (a) ESR spectroscopy in proving the covalency in M-L bonds; (b) Mössbauer spectroscopy for inorganic compounds.

 

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        LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 48

FOURTH SEMESTER – April 2009

CH 4809 – APPLICATIONS OF SPECTROSCOPY

 

 

 

Date & Time: 23/04/2009 / 9:00 – 12:00  Dept. No.                                                 Max. : 100 Marks

 

 

PART A

Answer all the questions.                                                                                   10 x 2 = 20

1. Calculate l_max for the following compounds
2. a)                        b)
3. Why the solution of iodine in hexane is violet while in benzene, it is brown?
4. Distinguish between maleic acid and fumaric acid using IR spectroscopy.
5. Why methyl alcohol is a good solvent for UV but not for IR determination?
6. State the fragmentation modes in benzene.
7. How does NMR distinguish between the isomers of a primary and secondary alcohol.
8. Compare the magnitude of ³J_HH with ²J_HH.
9. Solution spectra of a compound of lower symmetry is isotropic. Explain.
10. Which of the following is NQR active in solid state? NaCl or Cl₂.
11. High spin Fe3+ has zero quadrupole splitting while high spin Fe2+ has a large quadrupole splitting. Explain.

PART B

Answer any eight questions.                                                                                8 x 5 = 40

11. Predict the structure of the compound which shows m/e peaks at 88, 70, 55, 42, 31 (much intense) and 29.
12. a) which type of transitions are considered to be the origin of charge transfer bands?
13. b) Why hydrogen bonding shifts the absorption to shorter wavelengths in alcohols?
14. Distinguish between the following each pair using IR spectra.
15. a) acetone and acetylene
16. b) ethanol and ethanal
17. c) o-hydroxyl benzoic acid and m-hydroxy benzoic acid
18. d) phenol and cyclohexanol
19. e) aniline and N-methyl aniline
20. Interpret octahedral complexes of Mn²⁺ using Orgel energy level diagram.
21. Deduce the structure of the organic compound with the molecular formula C₈H₈O₂ which shows IR peaks at 3300, 1700, 3050, 2990, 1590 and 1540 cm^-1.
22. Explain the fragmentation pattern of acetophenone.
23. Explain the various coupling possible in an alkene and compare their magnitude.
24. Bring out the differences between homotopic, enantiotopic and diastereotopic protons.
25. a) How many lines are expected in the EPR spectrum of the free radical HBr^..
26. b) What is the spin of a single nucleus which gives three lines EPR spectrum. (3+2)
27. Explain the use of NQR technique in the determination of covalency of nickel and platinum complexes.

 

21. Which of the following hybridization accounts for a higher isomer shift? sp³ or d²sp³. Explain.
22. How many NQR transitions are possible for iodine and bromine in their solid state.

PART C

Answer any four questions.                                                                              4 x 10 = 40

23. Identify the compound with the molecular mass 72 which responds to iodoform test. It absorbs in UV spectrum at 275 nm (e_max is 17). In IR spectrum the various bands obtained are i) 2941 ii) 1715 and iii) 1460 cm^-1. In mass spectrum, the fragmentations are obtained at m/e values of 72, 43 (maximum intensity), 29 and 15. In NMR spectrum, three signals appear at i) quartet, 2.5 d, ii) singlet, 2.2 d, iii) 1.1 d.
24. a) Distinguish primary, secondary and tertiary alcohols by using mass spectroscopy with an example.
25. b) Explain the McLafferty rearrangement of 1-pentene. (8+2)
26. a) Explain the characteristic IR absorptions in ethyl acetate.

 

1. b) Calculate l_max for the following compounds
2. i) ii)

iii)                                                         iv)

1. v)                                                        (5+5)

 

26. a) 60 MHz proton NMR of toluene shows first order pattern while 300 MHz shows second order pattern. Explain.
27. b) How will you account for the splitting pattern of vinyl protons?                          (6+4)
28. a) What is quadrupole coupling constant? Explain the fact that the quadrupole coupling constant determined for chlorine molecule and chlorine atom are comparable.
29. b) Discuss the EPR spectrum of triplet naphthalene radical. (6+4)
30. a) What is hyperfine splitting? Explain the hyperfine splitting caused by a quadrupole nucleus.
31. b) Discuss the effect of coordination number on isomer shift and quadrupole splitting in tin compounds.                                                                         (5+5)

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FOURTH SEMESTER – APRIL 2012

CH 4809 – APPLICATIONS OF SPECTROSCOPY

 

 

Date : 18-04-2012             Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

 

PART A

Answer all the questions                                                                                                                 10×2=20

 

1. State the fragmentation modes of benzene.
2. Mention the characteristic peaks of an acid anhydride in IR spectra.
3. What is transannular conjugation? Give an example.
4. Why a polar solvent usually shifts π®π* transition to longer wavelength and

n®π* transition to shorter wavelength?

5. Mention any two characteristic signals of primary alcohols in mass spectroscopy.
6. What is the significance of spectral editing?
7. Mention the conditions favorable for first-order coupling in NMR.
8. Compare the coupling constants in NMR and ESR spectra.
9. How does hydrogen bonding alter NQR frequencies?
10. What is the influence of energy of gamma ray on  f – factor?

 

PART B

Answer any eight questions                                                                                                       8×5=40

 

11. Identify an acidic yellow compound which gave the following data:
12. i) UV: 280 nm, e_max = 6600

ii)IR : 3460 cm^-1 (s), 3035 cm^-1 (m), 1510 cm^-1 (s), 1310 cm^-1 (s), 740 cm^-1 (s). The band at 3460 cm^-1 does not shift even on diluting the sample.

iii) NMR : -2.1t  (singlet) 1H and unsymmetrical pattern 2.61-2.75 t (4H).

12. Deduce the structure of the compound having the molecular formula C₅H₁₀O₂ giving effervescence with sodium bicarbonate. It shows the following mass spectral patter at m/e values: 102, 73, 60 (100% intensity), 57, 45 and 29.
13. Suggest the structure of the liquid compound with the molecular formula C₆H₆O showing a violet colour with neutral FeCl₃. The IR absorptions are at 3300 cm^-1, 3040 cm^-1,  1360 cm^-1,  1220 cm^-1 and 685 cm^-1.
14. Calculate L_max for the following compounds:
15. i) ii)

 

iii)                                                                                iv)

 

 

1. v)

 

 

 

 

15. Identify the compound with molecular mass 120 which shows a UV peak at 268 nm (e_max = 480).In IR spectrum absorption bands are found at 3067-2907 cm^-1 (m), 1608 cm^-1 (m), and 1473  cm^-1 (m). The NMR spectrum shows absorptions at 3.21t  (singlet) and 7.74t  (singlet).
16. Explain the IR absorption bands of aniline. The IR absorptions are at 3450 cm^-1,  3026 cm^-1, 1620, 1602, 1499 cm^-1, 754, 696 cm^-1, and  1306, 1257 cm^-1.
17. Sketch the ¹³C NMR of 2–butanone under i) broad band decoupling of ¹H and ii) coupling of ¹
18. Highlight the coupling involved in the ¹H NMR of 1 – nitro hexane.
19. What is hyper fine splitting? Discuss the hyper fine splitting exhibited by high spin Mn²⁺
20. How will you account for the trend, shown in the ionic character of the tetra chlorides of carbon group elements?
21. The compound NaAuCl₄.2H₂O shows four NQR lines. One of the lines shows positive temperature dependence – Explain.
22. Isomer shift measures principally the difference in valence s-orbital populations – Explain.

 

 

 

 

 

PART C

Answer any four questions                                                                                        4×10 = 40

23. An organic compound with the molecular mass 108 is not acidic in nature, but can be easily oxidized to a crystalline compound. In UV, it absorbs at 255 nm (e_max =202). The IR spectrum shows absorptions at 3402 cm^-1 (s,b), 3065 cm^-1 (w), 2288 cm^-1 (w), 1499 cm^-1 (w), 1455 cm^-1 (m). The signals in NMR are 2.74t singlet, 5.4t singlet and 6.10t The mass spectral pattern shows m/e values at 108, 106, 105, 77, 51 and 39.
24. Explain the tetrahedral and octahedral complexes of Co²⁺ using Orgel energy diagram.
25. An organic compound with molecular mass 160 absorbs at 210 nm (e_max = 60) in the UV spectrum. In IR spectrum, absorption bands formed are at i) 2940-2855 cm^-1 (m), ii) 1742 cm^-1 (s), 1460 cm^-1 (m), 1055 cm^-1 (s), 1260 cm^-1 (s).  The following signals are formed in NMR spectrum i) 7.5 t singlet, ii) 8.71 t triplet, iii) 5.84 t Deduce the structure of the compound and suggest its mass spectral pattern.
26. a) What is COSY? Explain with an example, the influence of a prochiral centre in COSY.
27. b) An enolic proton is downfield compared to an alcoholic proton – explain.
28. a) How will you account for the transitions, shown by the interaction of an electron with three equivalent protons?

b)³⁵Cl NQR of hexachlorocyclopentadiene shows two lines in 2:1 intensity ratio. Arrive at the point group symmetry of the molecule.

28. a) Define: Isomer shift and Quadru pole splitting. How are they exhibited by high spin Fe²⁺ and Fe³⁺
29. b) How many NQR transitions are possible for ⁵¹V nucleus.

 

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