II Semester M.Sc. in Chemistry Examination February 2015 Organic Chemistry

Time: 3Hours Max. Marks: 80

Instructions: PART- 1 is compulsory and answers any four of the remaining questions from PART-II

PART-1 Answer any 8 questions 2 x 8=16 i) What is Luche reduction? Give one example. ii) Explain chemo selective reaction with example. iii) Comment on aptitude of migrating group in pinacol-pinocolone rearrangement. iv) Explain Benzylic acid rearrangement. v) What is the intermediate involved in Schemidt rearrangement. vi) What is menat by enantiomeric excess (ee)? vii) Explain Deals-Alder reaction? Give one example viii)What is Chichibaby reaction? ix) What is chiral auxylary? Give one example. x) Write any two acid labile protecting group used for protection of alcohol group. PART-II 1. a) Predict the structure of the product formed in the reaction below b) With example, explain the use of lead teraacetate in organic synthesis. And write the mechanism. c) With example discuss followings i) Ring closing mechanism (RCM) ii) Cross methathesis and iii) Ring opening methathesis (4 + 6 + 6) 2. d) What is Corey-Kim oxidation? Illustrate with example. e) Explain the radical Mechanism of halogination of alaknes. f) What is birch reduction? With example explain the stereochemistry of product in reduction of alkyne using birch reduction (4 + 6 + 6) H- C CH i) NaNH2 ii) CH2 - CH2 - Br A i) NaNH2 ii) Br B3. g) What is Fries rearrangement? Discuss with mechanism. h) What is Beckman rearrangement? Discuss the mechanism and comment on aptitude of migration group. i) Illustrate Rabinsion annulations reaction? Explain the mechanism with example. (4 + 6 + 6) 4. j) Explain the enetioselective and diastereoselective addition to carbon-carbon double bond. k) What is conjugate addition reaction? What are the factors influence regeoselectivity in conjugate addition reaction? l) With example discuss orthogonal protection strategy. (4 + 6 + 6) 5. m) How phosphorus and sulphur ylids reacts with carbonyl compounds? Write the reaction mechanism in both reactions. n) Write the any two major reactions of N-halo succinamides in organic synthesis. o) Write the structure of products in the following reaction. (4 + 6 + 6)

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