Units-1 & 2: Pericyclic Reactions

Transcription

1 Units-1 & 2: Pericyclic Reactions Section-A: Each question carries 5 marks. 1. Write the Molecular orbitals of ethylene and explain number of nodes, symmetry properties of molecular orbitals. 2. Write the Molecular orbitals of allyl radical and explain number of nodes, symmetry properties of molecular orbitals. 3. Write the Molecular orbitals of allyl cation and explain number of nodes, symmetry properties of molecular orbitals 4. Explain Suprafacial & antarafacial interactions of 4n system in cycloadditions. 5. Explain Woodward-Hoffmann rules by taking Diels-Alder reaction as an example. 6. Write the structure and symmetry properties of molecular orbitals of pentadienyl radical. 7. Write Woodward Hoffmann selection rules for cycloaddition reactions. 8. Trans, cis-2,4-hexadiene in thermal condition gives A where as in photochemical condition gives B. What are A & B. 9. Write the structure and symmetry properties of molecular orbitals of 1,3- butadiene radical. 10. Classify Pericyclic reactions giving one example for each class. 11. Discuss the mechanism of [1, 3]-H shift suprafacial using FM method & indicate under which conditions the reaction is allowed. 12. Write Woodward Hoffmann selection rules for 4n+2π electron system with stereochemical aspects. 13. Write the pentadienyl radical molecular orbitals and mention the no.of nodes present in each M., symmetry elements & also indicate HM-LUM levels in the ground state & first excited state. 14. Define Pericyclic reactions. What are the characteristic features of pericyclic reactions? 15. Write all the molecular orbitals of 1,3,5-hexatriene & indicate HM and LUM in ground state and first excited state. 16. Dimerisation of ethylene is photochemically allowed. Explain this by FM approach.

2 17. Frame the selection rules for Electrocyclic reactions based on FM approach. 18. Write the selection rules for Electrocyclic reactions based on ATS approach. 19. Write the selection rules for cycloadditions based on FM approach. 20. Predict the products for following reactions. a. CH 2 =CH--CH 2 -CH=CH 2? b.trans,cis-2,4-hexadiene? 21. Frame the selection rules for sigmatropic reactions by ATS approach where chiral group migrations are involved. 22. Predict the products for following reactions. 23. Attempt the following conversion with comments.

3 24. Write the pentadienyl cation molecular orbitals and mention the no.of nodes present in each M., symmetry elements & also indicate HM-LUM levels in the ground state & first excited state. 25. Write the pentadienyl anion molecular orbitals and mention the no.of nodes present in each M., symmetry elements & also indicate HM-LUM levels in the ground state & first excited state. 26. Write about cope rearrangement by taking an example 27. Define the following with examples of reactions: a. Electrocyclic reactions b. Sigmatropic reactions 28. Define the following with examples of reactions: a. Cycloaddition reactions b. Chelotropic reactions 29. Define the Following terms with examples: a. CN & DIS Rotation b. Suprafacial & antarafacial shift c. HM & LUM levels d. Huckels Aromatic transition state e.mobius antiaromatic transition state. 30. Write the classification of transition states based on number of nodes & electron system. 31. Discuss the mechanism of [1, 3]-H shift antarafacial using PM method & indicate under which conditions the reaction is allowed. 32. Discuss the mechanism of [1, 5]-H shift suprafacial using FM method & indicate under which conditions the reaction is allowed. 33. Discuss the mechanism of [1, 5]-Suprafacial sigmatropic shift of asymmetric carbon atom with retention & inversion of configuration using FM method & indicate under which conditions the reaction is allowed. 34. Discuss the mechanism of [1, 3]-antarafacial sigmatropic shift of asymmetric carbon atom with retention & inversion of configuration using PM method & indicate under which conditions the reaction is allowed. 35. Explain 2πs+2πs & 2πs+2πa cycloadditions based on FM approach & indicate under which conditions the reaction is allowed. 36. Explain 4πa+2πa & 4πs+2πa cycloadditions based on PM approach & indicate under which conditions the reaction is allowed.

4 37. Explain the reaction conditions for the electrocyclic DIS ring closure of hexatriene to cyclohexadiene based on PM approach 38. Explain the reaction conditions for the electrocyclic DIS ring closure of butadiene to cyclobutene based on FM approach Section-B: Each question carries 10 marks. 1. a. Write Woodward-Hoffmann selection rules for electrocyclic reactions. b. In the below given example, find out A & B 2. a. Explain Claissen Rearrangement with suitable example. b. Explain 1,3 & 1,5 shift of hydrogen suprafacially & antarafacially in sigmatropic reactions. 3. a. Explain the principle of Conservation of orbital symmetry in Electrocyclic reactions. b.write the selection rules for electrocyclic reactions based on Huckels- Mobius method. 4. a.write the structures of the products with PM approach.

5 b.write the selection rules of Electrocyclic reactions based on FM approach. 5. a. Write the Molecular orbital diagrams for 1,3,5-hexatriene & indicate their symmetry properties. b. Explain the mechanism of DIS type of ring closure of 1,3,5- hexatriene using conservation of orbital symmetry method. 6. a. Write the Molecular orbital diagrams for 1,3,-butadiene & indicate their symmetry properties. b. Write briefly on Huckel- Mobius aromatic transition state method for Electrocyclic reactions. 7. a. What are selection rules for [1,j] shifts. Explain their mechanism using symmetry properties of HM of the polyenyl radical b.using rbital Symmetry Correlation diagram method, explain [2πs+2πs] cycloaddition. 8. a. Explain the terms CN & DIS rotation w.r.t. Electrocyclic reactions. b.define Huckel polyene system & Mobius polyene system. Enumerate difference between them. 9. a. Write the products of concerted cycloaddition of ethylene & trans-2-butene addition being suprafacial on both components. Explain whether it is thermally or photochemically allowed. b.predict the product & explain the mechanism for the following reaction:

6 10. a. Draw the CD for CN mode of Electrocyclisation in hexatriene to cyclohexadiene reaction. Predict & explain whether reaction is allowed thermally or photochemically. b.describe the following cycloadditions with examples. i) 4πs +2πs ii) 4πs +2πa iii) 4πa +2πs iv) 4πa +2πa 11. a. Predict & explain whether the transformation of Cyclobutene to butadiene by CN rotation is allowed thermally or photochemically. b.[1,5] suprafacial migration of sigma bond is allowed thermally but photochemically forbidden. Explain by using FM approach. 12. a. Explain PM method by taking electrocyclic reactions. b.trans, cis, trans-2,4,6-octatriene in thermal condition gives compound A where as in photochemical condition gives compound B. Compound B again in thermal conditions gives C. What are A,B & C? 13. a. Explain the mechanism of Cope rearrangement with suitable examples using FM approach. b. Explain the 1,5-sigmatropic shift of asymmetric C atom with retention & inversion configuration. 14. a. Discuss the mechanism of Diels alder reactions using FM theory & indicate the reaction is allowed under which conditions. b. Write the products formed in the below given examples.

7 15. a. Explain Claissen Rearrangement with suitable example. b. Explain 1,3 & 1,5 shift of hydrogen suprafacially & antarafacially in sigmatropic reactions. 16. a. What are Pericyclic reactions? Classify them. b. Write the Molecular orbitals of pentadienyl cation, and which one is HM in thermal condition. 17. a. Discuss mechanism of DIS type of electrocyclic ring closure of 2E,4Ehexadiene using aromatic transition state theory and indicate the stereochemistry of the product b.write the Molecular orbitals of pentadienyl cation, and which one is HM in thermal condition. 18. a. What are chelotropic reactions, give two examples. b. Explain Huckel-Mobius Aromatic and Antiaromatic (PM) transition state theory. 19. a. Explain the mechanism of DIS type of enclosure of 1,3,5-hexatriene using conservation of orbital symmetry method. b. Discuss the mechanism of CN type of enclosure of 1,3-butadiene using FM approach and indicate the reaction is thermal or photochemical. 20. a. What do you understand by 2πs+2πs cycloadditions. Discuss the mechanism by aromatic transition state theory b. Discuss the mechanism of Diels-Alder reaction using FM theory and indicate the reaction is allowed under which conditions.

8 21. a. Discuss the mechanism of [ 1,3] and [1,5] suprafacial hydrogen shift reactions using aromatic transition state theory b. Explain the mechanism of Cope rearrangement with suitable examples using FM approach. 22. a. Trans, cis, trans-2,4,6-octatriene in thermal condition gives compound A where as in photochemical condition gives compound B. what are A & B? b. Write the Molecular orbitals of 1,3,5-hexatriene. 23. a.explain PM method by taking electrocyclic reactions as example b. Write the woodward-hoffmann selection rules for 4nπ electron system for CN electrocyclisation. 24. a. Write Cope & claissen rearrangement with suitable examples. b. Write the products formed in the below given examples. 25. a. Explain the 1,5 sigmatropic shift of asymmetric C atom with retention & inversion configuration. b. Write the products formed in the below given examples.

9 26. a. Explain Diels alder reaction using rbital Correlation diagram method in which both the components are approaching suprafacially. b. Write about chelotropic reactions & explain the mechanism by FM theory. 27. a. Draw the CD for DIS electrocyclic ring closure of butadiene to cyclobutene b. Write short notes on the following: i. Endo-Exo selectivity in Diels alder reaction ii. Cope rearrangement. 28. a. Write the selection rules of Sigmatropic reactions based on FM theory b. Write a note on Claissen rearrangement. 29. a. Discuss the mechanism of [1,5] antarafacial sigmatropic shift of asymmetric carbon atom with retention & inversion configuration based on PM approach b. Draw the CD for DIS electrocyclic ring closure of hexatriene to cyclohexadiene 30. a. Draw the CD for CN electrocyclic ring closure of hexatriene to cyclohexadiene b.discuss the mechanism of [1,3] antarafacial sigmatropic shift of asymmetric carbon atom with retention & inversion configuration based on FM approach

10 Unit-3:SYNTHETIC STRATEGIES-I SECTIN- A (5Marks) 1) a)define the following with suitable examples i) Target molecule ii) Reagent iii) Retrosynthesis b) Explain one group C-X disconnections with suitable examples 2) a)give examples for one group C-C disconnections. b) Write a note on Michel Addition. 3) Discuss the preparation and role of a synthon in synthesis. 4)Define the terms: synthon,target and FGI 5) List of order of events in rganic synthesis 6)Discuss the importance of chemical degradation and Retro Mass spectral fragmentation in organic synthesis. 7)Which of the following is correct disconnection. Explain A CH 3 a Br + CH 3 b + Cl CH 3 Et Et Et B Cl a Cl N 2 b Et Et 8) Explain with suitable examples the terms synthon, Synthetic equivalent, disconnection and transform. 9) Discuss the disconnection approach for organic synthesis with one suitable example. 10) Describe the Criteria for target selection with appropriate examples. 11) Define and illustrate the following terms i) Retrosynthesis ii) Synthons iii) Transform 12) List the criteria for target selection, and discuss any one criterion with suitable example. N 2

11 13)Write the synthons and the respective synthestic equivalents for the disconnections shown in the target molecule. b a? b H a? 14) Define the following terms with suitable examples i) Functional group Interconversion ii) Synthetic Equivalent 15) What are synthons? Illustrate their importance in the synthesis of p-methoxy acetophenone. 16)Explain the terms linear and convergent synthesis with suitable examples 17) Write the retrosynthetic analysis and synthesis of the following H H H NBu-t 18) a) Explain retrosynthetic analysis involving chemoselectivity with examples b)explain one group C-X disconnections with suitable examples 19)a)Define Synthon. Explain linear and convergent synthesis with examples. b) Discuss the synthons & synthetic equivalent involved in the retrosynthesis of CH I ) II ) H 2 N H 3 C C H CH 20) Explain the following with suitable example I)Synthon II) FGI 21) What is regioselectivity? Explain with two examples

12 22) Explain the following with suitable examples. a) Synthon b) Target molecule c) Regioselectivity. 23) Explain the following terms with suitable examples i)chemoselectivity ii)regioselectivity iii)stereoselectivity 24) Define and illustrate with examples the linear and the convergent synthesis. 25)Write the retrosynthesis of salbutamol 26) Explain about one group C-X disconnections of alcohols and ethers. 27)Write the retro synthesis of Dinocap. 28) Explain the retrosynthesis of propaxycaine

13 SECTIN- B(10Marks) 1)(a) Explain the following with suitable examples i)chemo selectivity ii) Stereo selectivity b) Discuss convergent synthesis with suitable examples. 2) a)discuss the following i) Amine synthesis ii) Reversal of Polarity b) Discuss order of events in organic synthesis 3)a)Discuss the criteria for disconnection of bonds in carbocyclic rings. b)write about Johnson polyene cyclization. 4)a) Give the synthesis of the following. i) (+) Disparlure ii) Z-Jasmone 5) Write notes on i) Chemical Degradation ii) Mass Spectral degradation. 6)a) Discuss the concept of Linear and Covergent syntheses with examples. b) What is meant by syntheses umpolung state and explain Robinson annulations with examples. 7)a) What is meant by two group dicsconnections? Explain two group C-C disconnections with examples. b)differentiate between chemoselectivity and regioselectivity with examples. 8)a)Illustrate Functional Group Interconversion, Functional Group addition with examples. b) What are one group C-X disconnections?illustrate with Examples. 9) a) Show the appropriate disconnection and formulate the synthesis of b)with a suitable example explain linear synthesis. 10) Taking suitable examples explain i) Linear and convergent synthesis ii)importance of order of events in rganic synthesis

14 11) a) Formulate the retrosynthesis of the following molecules b)explain the reversal of polarity with any three examples. 12) a)define and illustrate retrosynthesis with any examples. b)describe the importance of FGI in organic synthesis. 13)Explain one and two group disconnection in 1,3 dicarbonyl compounds with suitable examples. 14) How do you plan for the synthesis of aspirin and paracetamol by retrosynthetic analysis. CCH 3 15) Write the order of synthesis of by retrosynthetic analysis 16) a)what is convergent synthesis? Device a convergent synthesis for the following molecule. Ph Ph b) Write the retrosynthetic analysis and synthesis of the following. Ph 17)a) Define and illustrate the following terms i) Stereoselectivity Ph

15 ii)regioselectivity b) Discuss two group C-X disconnection with suitable examples 18) What do you mean by order of events in organic synthesis?explain its importance by taking the following target molecule. CH 3 19)Using disconnection approach give the best possible retrosynthesis and the following target molecules i) Ph ii) Ph 20) In the retrosynthesis of an amine the one group C-X disconnection is not with while to begin with. Explain this observation with examples and suggest an alternate retrosynthetic analysis for amines. 21)In how many ways can you disconnect the following target molecule in its retrosynthesis?give in each case the synthons, synthetic equivalents and the corresponding synthesis. C 2 H 22)a)Explain the C-C disconnection of Michel addition and Robinson annulations with suitable examples. b)what is strategic bond? Discuss the one group and two group C-X disconnections with examples. 23) a)what is disconnection approach and explain the guidelines for disconnection approach? b) How do you prepare Benzocaine with disconnection approach.. H 2 N C Et

16 24)a)What is synthetic tree? Explain linear & convergent methods with suitable examples. b)what is umpolung? Explain with suitable example. 25)What is convergent synthesis? Describe a convergent synthetic method for the following. H 26) Using disconnection approach outline the synthesis of the following target molecule. Indicate the synthons and synthetic equivalents. 27)a) Give two examples each for stereoselective synthesis and chemoselectivity b)illustrate one group C-X disconnection with suitable example. 28)a)Using disconnection approach outline the synthesis of the following target molecule.indicate the synthons and synthetic equivalents involved. H b) Discuss two group C-X disconnection with suitable examples. 29)a) Describe chemical degradation approach and retro mass spectral fragmentation in retrosynthesis. b) Write the products and suggest suitable mechanism in the following Silver acetate and iodine anhydrous conditions?

17 30 a) Formulate the retrosynthesis of the following molecules 0 H 2 C C 2 H i ii H 2 C C 2H b) Explain the order of events in organic synthesis. Provide examples. 31)a) Define the terms regioselectivy, stereselectivity and chemoselectivity.explain with examples. b) what are synthetic equivalents? Discuss the use of two synthetic equivalents in organic synthesis. 32) Discuss the importance of retrosynthetic analysis and applications in organic synthesis. 34) Using the disconnection approach suggest a method of synthesis H H C 6 H 5 Unit-4: SYNTHETIC STRATEGIES-II SECTIN- A (5Marks) 1) Give an example for one group C-C bond disconnection 2) What is the criteria for disconnection of strategic bonds in carbocyclic rings. 3) What is disconnection approach? Explain with suitable example. 4) Explain the term one group C-X disconnection with suitable example. 5) Define and explain the following terms i) Johnsons polyene cyclization ii)synthesis of (+) Disparlure 6)a) Explain the term disconnection approach with suitable examples. b)write a note on Johnson polyene cyclization 7)Explain with examples biomemetic and chemical degradation approaches to

18 retrosynthesis. 8) Using disconnection approach give the retrosynthesis and synthesis for the following molecule. 9) Citing an example explain the importance of chemical degradation approach as an alternate for retrosynthesis by disconnection approach. 10) What is the criteria for disconnection of strategic bonds in carbocyclic rings? 11) Give an example for one group C-C bond disconnection 12) Discuss two group C-X disconnection wih suitable examples. 13) Give the synthetic strategies for Longifoline. 14) Give examples for one group C-C disconnections. 15)Write a note on Michel Addition. 16)Discuss the importance of chemical degradation and Retro Mass spectral fragmentation in organic synthesis. SECTIN-B (10Marks) 1) a)apply the strategy for the synthesis of (+) Disparlure b)write a note on Johnsons polyene cyclization. 2)Write the retrosynthetic analysis for the following compounds. 3) a)write the retrosynthetic analysis for the following compounds

19 b) Apply the strategy for the synthesis of Z-Jasmone 4)a)Describe chemical degradation approach and retro mass spectral fragmentation in retro synthesis. b)suggest the reagents with suitable mechanism in the following conversions. H?? H H H 5) a) write the structures of intermediates in the synthesis of retroneciene N H CEt CEt H NaBH 4 H A 1)Ba(H) 2 2) HCl 1.Ac 2 2.t-BuK 3. BIBAL-H E B BrCH 2 CEt Na 2 C 3 EtH NaBH 4 C D 1Na Et 2NaH N b) Write notes on i) Synthesis of (+) Disparlure ii)biomimetic approach in retrosynthesis 6)a) Using disconnection approach outline the synthesis of the following target molecule,indicate the synthons and synthetic equivalents involved

20 b) Write note on Biomimetic approach in retrosynthesis 7)a)Write the retrosynthetic analysis and corresponding synthesis of retroneciene. b) Describe the synthesis of Longifoline. 8) a) Describe the synthetic strategies for the following H H H N b) Write the retrosynthetic analysis and synthesis of the following 9) a)suggest suitable mechanism in the following conversion. 1) tbuh,h + 2) LAH,ether,H 2 3)(AC) 2,pyridine H + H

21 b) Give the synthetic strategies for Z-jasmone 10)a)What is a strategic bond? Give an account of the criteria for disconnection of strategic bonds. Illustrate your answer with suitable examples. b)what is meant by one group disconnections? Explain with any two examples. 11) Using disconnection approach outline the synthesis of Z-Jasmone and Retonecine. 12) a)define a strategic bond for disconnection.explain clearly by taking an example, maximium bridging ring in which a strategic bond is located b) Write the retosynthesis and synthesis for (+) Disparlure by using disconnection approach. 13)a)Discuss the use of mass spectrometry as an alternate for the disconnection approach. b) utline the most suitable retrosynthesis and the synthesi for the following target molecules. Give the synthons and synthetic equivalents involved. i) ii) RR 1 R 2 CH C 2 R 14) Derive the synthesis of the following molecule using retrosynthetic analysis i) (+)-Disparlure ii) Retronecine 15) Give an account on Johnsons Polyene Cyclisation. 16)Explain the retrosynthesis and synthesis of Michael Addition and Robinson Annulation 17) a)what is strategic bond? Discuss the one group and two group C-X disconnections with examples. b) Write the retro synthetic analysis and synthesis of (+)Diparlure. 18)a)Discuss the criteria for disconnection of bonds in carbocyclic rings. b)write about Johnson polyene cyclization. 19) a) Give the synthesi of the following i) (+) Disparlure ii) Z-Jasmone b) Write notes on i) Chemical degradation ii) Mass Spectral degradation 20)Design the synthesis of retronecine and longifoline based on disconnection approach. 21) Write notes on i) Johnson polyene cyclization ii)criteria for disconnection of strategic bond 22) Explain about control in carbonyl condensations by taking with examples oxanamide and mevalonic acid.

22 23) Write the guide lines for disconnection of C-X bonds. 24) Explain two group C-C disconnections by taking example Diels Alder reaction. 25) Explain two group C-X disconnections of 1,1,1,2 and 1,3 difunctionalised compounds.