Download PTU M-Sc -Chemistry 1st Semester May 2019 51143 ORGANIC SPECTROSCOPY Question Paper

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Total No. of Pages : 02

Total No. of Questions: 19

M.Sc.(Chemistry) (Campus) (2015 to 2017) (Sem.-1)

ORGANIC SPECTROSCOPY

Subject Code : CHL-404

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M.Code: 51143

Time: 3 Hrs.

Max. Marks : 70

INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.

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2. SECTION-B contains SIX questions carrying FIVE marks each and students have to attempt ALL questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

1. Which is the main component of mass spectroscopy deal with resolving the ions into their characteristics mass components according to their mass-to-charge ratio?
2. Why the magnitude of coupling constant is higher in the case of benzene rather than cyclohexanes?

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3. In which state of matter mass spectroscopy is being performed?
4. What transition is not observed by general UV-Vis spectrophotometer?
5. When you use CDCl3 as a solvent in ¹³C NMR, why are getting extra triplet at ~ 76 ppm?
6. How will you calculate the coupling constant in a given ¹H-NMR spectra?
7. What is the essential condition for a molecule to be IR active?

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8. Write the possible electronic transitions in the benzaldehyde.
9. Why Aniline shows blue shift in acidic medium?
10. Which bond will vibrates faster between following combinations?
    1. C-H or C-D
    2. C-O or C-Cl

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SECTION-B

11. A compound C₁₀H₁₃Cl gave the following NMR data : d 1.57, singlet, 6H; d 3.07, singlet, 2H; d 7.27, singlet, 5H. Deduce the structure of compound.
12. Write a short note on McLefferty rearrangement.
13. How would you distinguish ethylamine, diethylamine and triethylamine using Electronionization mass spectrometry (EI-MS) technique?
14. A compound C₁₀H₁₄ gave the following NMR data: d 0.88 (d, 6H); 1.86 (m, 1H); 2.45 (d, 2H); 7.12 (s, 5H). Deduce the structure of compound.

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15. Write a short note on the importance of DEPTH technique in ¹³C NMR spectroscopy.
16. Why the intensity of N-H and O-H absorptions is stronger than C-H absorption?

SECTION-C

17. How do the following factors affect vibrational frequency in infrared spectroscopy?
    1. Hydrogen bonding
    2. Inductive effect and conjugation

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18. Explain chemical ionization method uses in mass spectrometry. Why does chemical ionization method give (M+1)^* peak? Describe using chemical equations.
19. Spectral data are given below, determine the structure :
    Molecular formula : C₄H₆O
    IR frequencies in cm^-1 : 2855, 2740, 1700, 1650
    

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    ¹H-NMR: 9.7 (1H, d), 6.7 (1H, dq), 6.9 (1H, dd, J=7 & 17 Hz), 2.5 (3H, d).

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