Download PTU B.Sc-BT 2020 March 3rd Sem 47034 Organic Chemistry Question Paper

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Roll No. | Total No. of Pages : 02
Total No. of Questions : 09

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INSTRUCTIONS TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

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1. Write briefly :
   1. Define Resonance Energy. How does it affect the stability of the molecule?
   2. Explain that aryl halides are less reactive than alkyl halides.
   3. What are free radicals? Discuss the structure of a simple alkyl free radical.
   4. What is isotope labeling? Discuss its importance in determining the mechanism of an organic reaction.
   5. Explain briefly radical polymerization with suitable example.

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   6. What do you understand by (4+2) cycloaddition reactions?
   7. Draw the orbital structure of acetylene.
   8. Although benzene contains three double bonds, it resists addition reactions. Why?
   9. Why phenol has smaller dipole moment than methanol?
   10. How will you convert an acid chloride into anilide?

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SECTION-B

2. Spectroscopic measurements indicate that both the C-O bonds in sodium formate and all the C-C bonds have the same bond lengths of 1.27 A and 1.39 A respectively. Explain.
3. Out of (CH3)3C+ and (CD3)3C+, which carbocation is more stable and Why?
4. What is Lederer-Manasse reaction? Give its mechanism. Using this reaction, how will you explain the formation of Bakelite from phenol and formaldehyde?

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5. Dehydration of 1-butanol and 2-butanol give the same mixture of alkenes. Explain.
6. Comment on the statement “Delocalization alone is not a sufficient criterion for a molecule to exhibit aromaticity”.

SECTION-C

7. 1. Discuss briefly the conformations of cycloalkenes.
   2. Briefly discuss the methods of preparation of conjugated dienes.

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8. 1. Write a detailed note on allylic halogenation.
   2. Though benzene is an unsaturated hydrocarbon yet it fails to give Baeyer’s test. Explain.
9. 1. How will you prepare phenols from Grignard’s reagent?

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   2. How will you prepare n-valeric acid from acetoacetic ester and benzoic acid from benzene (using nitrile synthesis)?

NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any page of Answer Sheet will lead to UMC against the Student.

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