Chem 112 -final 2003

Pokhara University (B.Sc. Biochemsitry) 1st set Final Examination - 2003 Subject : Chem112 Organic Chemistry I

F.M : 100 P.M : 50 Time: 3 hrs

Candidates are required to give their answer in their own words as far as practicable. The figures in the margin indicate the full marks. Group: A Answer any three questions. Questions are of equal value. 3 X14=42 1. Discuss giving examples the kinetic and non kinetic methods of determining reaction mechanism. 2. What is enantiomerism? How do you predict enantiomerism? Explain the phenomenon by tetrahedral theory of carbon atom. Mention in which properties the enantiomers differ. 3. Explain the stereochemistry of SN1 and SN2 reaction. 4. Explain the E2 mechanism and reactivity for dehydrohalogenation reaction. Group: B Answer any six questions. Questions are of equal value. 6 X7 = 42 1. Explain briefly the energetics of reaction. 2. Describe the methods of generation of carbenes and nitrenes. 3. Define conformation of a molecule and conformational analysis. 4. Explain the factors affecting stability of conformations. 5. What happens when tert - Butyl alcohol is treated with conc hydrochloric acid? Also mention the mechanism for the reaction. 6. Write a short note on Pyrolysis. 7. Prepare an alkene from dehydration of alcohol & mention its mechanism. 8. What happens when 2-hexene is treated with ozone in presence of reducing agent? Group: C Answer any eight questions. Questions are of equal value. 1. Define functional groups giving examples. 2. Give examples of substitution and elimination reactions. 3. Give examples of Electrophiles and Nucleophiles. 4. Give examples of Z and E isomers. 5. Write the R and S configuration of CHClBrI molecule. 6. State Bayer’s Strain Theory. 7. Why do alcohols act as acids and bases? 8. Give one method for the preparation of alkyl halide. 9. What are Grignard reagents? 10. Why does cis-2-butene have greater boiling point than tras-2-butene? 11. What is Markovnikov' s rule? 12. Give an example of electrophilic addition.

8 X 2 = 16

Pokhara University (B.Sc. Biochemsitry) 2nd Set Final Examination - 2003 Subject : Chem112 Organic Chemistry I

F.M : 100 P.M : 50 Time: 3 hrs

Candidates are required to give their answer in their own words as far as practicable. The figures in the margin indicate the full marks. Group: A Answer any three questions. Questions are of equal value.

3 ´ 14 = 42

1.

Define reaction mechanism? Explain giving one example in each mechanism of the following types of reactions. (a) Addition reaction (b) Substitution reaction (c) Elimination reaction (d) Rearrangement reaction 2. What is optical activity? How is it measured? What is the essential condition for a compound to be optically active? How does the tetrahedral Theory of carbon atom explain emantiomerism of lactic and tartaric acids? 3. What happens when halogens are reacted with alkane? Explain the mechanism and orientation of halogenation. 4. What is dehydrohalogenation? Prepare 2-butene and 1-butene by using this reaction. Mention the mechanism of the reaction.

Group: B Answer any six questions. Questions are of equal value. 6 ´ 7 = 42 1. Describe the methods of generation of free radicals and Carbocations. 2. Write briefly the concept of organic acids & bases. 3. How do you specify R and S configuration as well as Z and E isomers? 4. Explain the factors affecting the stability of conformations. 5. Give four reactions for the preparation of ether. 6. The given reaction is of second order kinetics. Identify the type of reaction and give its mechanism. Also give a short account on stereochemistry. CH3Br + OH- à CH3OH + Br8. Complete the chemical reaction given below:

Group: C Answer any eight questions. Questions are of equal value. 1. 2. 3. 4. 5.

What is a benzyne? What do you mean by pKa? Give examples of heterolytic fission. How can you prepare Grignard reagent? What is alkyl sulfonate?

8 ´ 2 = 16

7. Why is dehydration of alcohol done in presence of acid? 8. Write the product of the given chemical equation. CH3CH = CHCH3 + HI à 9. What is hydroxylation? 10. Explain very briefly Bayer' s Strain theory. 11. Define conformational analysis. 12. Define Diasteromer and meso compound. ***