LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
M.Sc. DEGREE EXAMINATION - FOOD CHEMISTRY
DB 33
FIRST SEMESTER – November 2008
FP 1802 - APPLICATIONS OF SPECTROSCOPY
Date : 12-11-08
Time : 9:00 - 12:00
Dept. No.
Max. : 100 Marks
PART - A
Answer ALL the questions.
(10 x 2 = 20 marks)
1. Why is water not used as solvent in IR spectroscopy?
2. Why does IR absorption due to carbonyl stretching occur at higher frequencies than
stretching of the C=C bond?
3. Indicate the different chemical shift ranges in the 1H NMR spectrum of toluene.
4. 12C and 16O will not give NMR signals whereas 13C and 17O gives NMR signal. Give reason.
5. What is hyperfine structure in ESR spectra?
6. Write any four nuclei which can be studied in mossbauer spectroscopy.
7. What is meta-stable peak?
8. Distinguish between α- cleavage and β- cleavage in mass spectrum.
9. State the Beer- Lambert’s law.
10. Mention the advantages of atomic absorption spectroscopy over flame emission spectroscopy.
PART B
Answer any EIGHT questions.
(8 x 5 = 40 marks)
11. What are the IR active modes of free water molecule? Explain the influence of coordination
on these modes with example.
12. How the various geometrical isomers of octahedral complexes can be distinguished from
their IR spectra?
13. Discus the relationship between relaxation time and line broadening.
14. How many NMR signals would you expect in the following?
a) 1,3,5-trimethyl benzene
b) 1,1- dichlororethane c) allyl alcohol.
15. Discuss the NMR spectra of methanol at high and low temperatures.
16. Write any five differences between NMR and ESR spectroscopy.
17. Discuss the hyperfine splitting of methyl radical.
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18. The mass spectrum of ethyl butanoate shows two characteristic peaks at m/e= 88 and 60.
Explain the fragmentation.
19. Explain any five rules for predicting prominent peaks in mass spectrum with suitable examples.
20. Give an account of the effect of solvent polarity on the electronic transition.
21. Write a note on the flame excitation unit in atomic absorption spectroscopy.
22. Discuss in detail about the various types of interferences in flame spectrometry.
PART C
Answer any FOUR questions.
(4 x 10 = 40 marks)
23. How is IR used to determine the coordination sites and linkage isomerism of the following?
a) isomers of urea
b) Thiourea
c) Thiocyanide
24. What are the factors which affects the chemical shift? Explain the anisotropic effects of π
electron circulation in alkene, alkyne and aromatic ring systems.
25. a) Cyclohexane shows only one chemical shift at room temperature but two at low temperature . Why?
(5)
b) Find out and explain the type of coupling involved between 1H and 1H in the following
compounds
i)
ii)
(5)
26. How are high spin and low spin iron complexes distinguished by quadrupole splitting using
Mossbauer spectroscopy?
27. a) In the mass spectrum of ethyl benzene, prominent peaks appear at m/e= 106,
91 and 65. What are the most probable species responsible for these peaks?
(4)
b) Distinguish between 3- methyl and 4- methyl cyclohexene on the basis of mass
spectrometry.
(6)
28. a) What are the functions of flame in flame emission spectroscopy?
(3)
b) Discuss the applications of atomic absorption spectroscopy in the determination of
calcium and magnesium in water.
(7)
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