A1/PG2/15/A16 Reg. No

St. Joseph’s College of Arts & Science (Autonomous) St. Joseph’s College Road, Cuddalore – 607001 PCH701S - ORGANIC CHEMISTRY – I Time : 3 hrs Max Marks :75 SECTION – A (20X1=20) Answer ALL Questions I. Choose the correct answer 1. Meso-tartaric acid is? a) Sometimes optically active c) Sometimes optically inactive

b) Always optically active d) Always optically inactive

2. The most stable conformation for conformation for n-butane is a) Skew boat b) Eclipsed c) Gauche d) Staggered-anti 3. Which of the following is a base? a) Ammonia c)Hydrogen

b) Ethane d) Hydrogen iodide

4. Hammett equation relates a) The equilibrium constants for the reactions of aliphatic Compounds. b) Both equilibrium constants and rate constants for the reaction of meta and para substituted benzene derivatives. c) Both equilibrium constants and rate constants for the reactions of Ortho-subtituted benzene derivatives d) Equilibrium constants to rate constant for the reactions of meta and para substituted benzene derivatives. 5. The stability of free radicals. a) 30>20>10 c) 20>10>30

b) 10>20>30 d) allyl<10<20<30

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6. A carbocation is a) Electrophile c) Neutral

b) Nucleophile d) None of these

7. Decomposition of diazines will give a) Nitrenes c) Benzynes

b) Carbenes d) Free radicals

8. Hofmann rearrangement involves the intermediate of a) RNC b) RNCO c) RCNO d) RCN 9. CH3-CN ----LiAlH4--------> ? a) CH3-CH2NH2 b) CH3CHNH c) CH3CH3 d) CH3COOH+NH4+ 10. Clemenson reduction is the reduction of a) Alcohols c) Nitro compounds

b) Olefines d) Ketones

II. Fill up the blanks 11. How many optical isomers are possible for lactic acid-----------? 12. The bonding between hard acid and bases is ------and between soft acid and bases is-----------. 13. The shape of the carbocation is----------------. 14. A diazonium salt reacting with another compound containing a benzene ring is called----------------. 15. The reduction reaction p-nitrobenzaldehyde to give p-nitrobenzyl alcohol is catalysed by----------------.

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III. Match the following Reactions

Reagents

16. Sandmeyar reaction

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30amine

17. Wolf kishner reduction

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NaoH/Br2

18. Wittig reaction

-

Cucl

19. Hofmann rearrangemen

-

Ph3P=CH2

20. Somlet houser rearrangement

-

N2H4/KOH

SECTION – B (10X2=20) Answer any TEN Questions 21. What is Asymmetric synthesis? 22. Assign R and S notation for lactic acid. 23. What is sterospecific reaction? 24. Define the hammett principle? 25. What is wittig reaction? 26. Write the application of HSAB. 27. Write one example for Wagner Meerwein reaction. 28. Give one example for Favorski reaction. 29. What is NaBH4 with example?

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30. What is Ulmann reaction? 31. Write the Etard reaction. 32. What is sodium cynoborohydride reducing agent? SECTION- C (5X7=35) Answer any FIVE Questions 33. Assign R/S configuration for any two chiral allenes and biphenyls.

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34. a) Give the mechanism for Birch reduction. b) Draw the fisher projection formula for glyceraldehydes.

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35. Explain the hammett equation and it’s applications.

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36. Briefly explain the mechanism of pinacol-pinacolone rearrangement.

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37. Write the following reaction mechanism a) Beckmann rearrangement b) Stevens rearrangment

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38. Write the short note on following reactions a) Sandmeyar reaction b) Curtius reaction

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39. Write the following reactions. a) Explain the MPV reduction b) Synthetic importance of wolf kishner reductions

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