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IGNOU MCHE-12 (July 2025 – June 2026) Assignment Questions
1. a) How does conjugation affect the electronic transitions in organic molecules? Explain showing its effect on absorption maxima with the help of an example.
b) Describe the effect of substituent on the UV spectra of carbonyl compounds with the help of examples.
2. a) Differentiate between the following compounds on the basis of UV spectra. Explain your answer.
b) Predict the expected UV and IR spectra of the following compound.
3. a) Predict the max values of the following and explain your answer.
b) Explain the basis of 1H NMR spectroscopy. Which of the atomic nucleus out of 12C, 2H, 19F is not NMR active and which is NMR active? Explain you answer.
4. a) Why is TMS used as a standard in NMR spectroscopy. Explain what do upfield and downfield signify in a NMR spectrum.
b) Explain the solvent effect in the simplication of complex spectra taking a suitable example.
5. Interpret the NMR spectra of the following compounds. Give the expected values and explain your answer.
6. a) Write the principle of 2D NMR. How is it different from ID NMR?
b) List the benefits and limitations of COSY technqiue.
7. a) Describe the use of broadband decoupling and off resonance decoupling in 13C NMR spectroscopy.
b) Answer the following with respect to HMQC experiment.
i) its full form
ii) its role in NMR
iii) the type of nuclei involved
iv) type of spectrum obtained
8a) Differentiate between COSY and HETCOR experiments in 2DNMR.
b) What is meant by a base peak and a molecular ion peak in mass spectrum? How is mass spectrometry used in finding out mass of a compound? Explain.
9. a) Describe different ionisation methods involved in mass spectrometry.
b) Describe the concept of cleavages taking benzylic clevages in mass spectrometry.
10 a) Explain McLafferty rearrangement with the help of a suitable example.
b) What kind of information is available from UV, IR, NMR and Mass spectra of an organic compound. Explain with the help of an example.
