IGNOU CHE-05 - Organic Chemistry

1. (a) Give the IUPAC names of the following compounds: (b) Write the structure of the following compounds: (i) Pentanedinitrile (ii) N-ethyl-N-propylpropanamine 2. Discuss the optical activity of the following molecules giving suitable diagrams. (i) trans-dichloroethene (ii) meso-tartaric acid 3. Draw the conformations of 1,3-dimethylcyclohexane. Which of these conformations is more stable and why? 4. Draw the possible modes of vibrations of CH2 group present a molecule. 5. Briefly explain the guidelines/ rules to predict the relative importance of resonance structures in different molecules/species of organic compounds. 6. Define octane number. What are different factors affecting the octane number of a compound. Give examples of additives used to increase the octane number. 7. What is Witting reactions? Give the mechanism of this reaction. 8. (a) How can you distinguish between terminal and internal alkynes using IR spectrum? (b) How can you convert butane to 2-butyne. 9. Which position of naphthalene is more active towards electrophilic substitution? Explain giving suitable structures. 10. (a) Give any two methods of preparations of pyrrole. Also write the reactions involved. (b) Write the resonance structures of pyridine-N-oxide. 11. Discuss the reactivity of allylic and benzylic halides in nucleophilic substitution reactions. 12. (a) How will you prepare phenol from benzene? Give the sequence of the reactions involved. (b) Give the preparation and use of nitroglycerin. 13. Write the products of the following reactions of epoxides: 14. Write chemical reactions for the following named reactions: (i) Etard’s reaction (ii) Gattermann-Koch synthesis (iii) Gattermann synthesis (iv) Wacker process (v) Friedel-Crafts acylation 15. Write chemical equations and reaction conditions for any five methods of preparation of carboxylic acids. 16. What is Michael addition? Explain giving suitable example and the mechanism involved. 17. Discuss the reduction of alknoyl halides using different reagents. Write the reactions involved and the products formed. 18. (i) Explain Henry reaction by giving a suitable example. (ii) Write important uses of nitro compounds giving suitable examples. 19. How will you differentiate between primary, secondary and tertiary amines using nitrosation reaction? 20. Discuss the structure of starch giving the type of bonding and the components.

1. (a) Give the IUPAC namely of the following: (b) Explain the type of hybridisation is ethyne giving suitable diagrams. 2. (a) Draw the geometric isomers of 2,3-diiodopent-2-ene. Assign their configuration a E or Z. (b) How can these isomers the differentiated? 3. (a) What is Walden inversion? Explain giving a suitable example. (b) Write two more Fischer projections for the following compound: 4. (a) Write the isomers of pentane. Which isomer will have the highest melting point? Explain. (b) Which will have higher value-1,3-butadiene or 1,4-pentadiene? 5. (a) Label the acid-base and conjugate acid-conjugate base pairs in the following systems: (i) propanoic acid and water (ii) water and ethylamine (b) What are Lewis acids and Lewis bases? Give one example of each. 6. (a) How would you prepare alkanes from the following? (Give only one example). (i) Alkyl halide (ii) Carboxylic acid (iii) Alkene (b) Explain the following: (i) In the mass spectra, alkanes give a series of peaks separated by 14 mass units. (ii) Alkanes with odd number of carbon atoms have lower melting point than those with an even number of carbon atoms. 7. (a) Explain the following in one to two lines. (i) Alkenes are more soluble in water than corresponding alkanes. (ii) Addition reactions of alkenes are exothermic processes. (b) Complete the following reactions: 8. (a) How would you prepare a cis- and trans- alkenes from an alkyne? Give reaction for each. (b) Which one of the following is most basic? Justify your answer. alkanide anion; alkenide anion; alkynide anion 9. (a) Why does nitrobenzene does not undergo Friedel-Crafts alkylation? (b) What do you understand by para-directing activators, ortho-directing activators and meta-directing deactivators? 10. (a) Give the reactions for following conversions: (i) Furfural to furan (ii) Pyridine to 2-hydroxypyridine (iii) Thiophene to 2,5-dihydrothiophene (b) Give various resonance structures of carbocation formed during electrophilic substitution of furan. 11. (a) Discuss the advantages of crown ethers in organic synthesis? (b) Alcohols are not as strong acids as phenols, Explain. 12. Taking a suitable example for each, write the mechanism of following reactions: i) Haloform reaction ii) Aldol condensation 13. Explain the following reactions with the help of suitable examples: i) E2 reaction ii) SN 1 reaction 14. (a) How you will carry out following conversions? 15. Discuss the mechanism of Fischer esterification. 16. (a) How would you prepare 1, 2-benzenedicarboxylic acid by two different ways? (b) How can the above acid be converted to its anhydride and inside? Write chemical reactions for the concessions. What is an imide group? 17. (a) What is trans-esterification? Give an example. (b) Complete the following reactions: 18. (a) How will you prepare 1,4-dinitrobenzene starting from benzenamine? (b) Briefly explain the spectral characteristics of nitro compounds. 19. (a) Explain why the enantiomers of an amine cannot be separated while those of the quaternary ammonium compounds, these can be separated. (b) What is carbylamine reaction? Explain its use. 20. Discuss Edman degradation of a peptide giving suitable reactions.