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 FMO 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.O, symmetry elements & also indicate HOMO-LUMO

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 HOMO and

LUMO in ground state and first excited state.

16. Dimerisation of ethylene is photochemically allowed. Explain this by FMO

approach.

17. Frame the selection rules for Electrocyclic reactions based on FMO

approach.

18. Write the selection rules for Electrocyclic reactions based on ATS approach.

19. Write the selection rules for cycloadditions based on FMO approach.

20. Predict the products for following reactions.

a. CH2=CH-O-CH2-CH=CH2 ?

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.

24. Write the pentadienyl cation molecular orbitals and mention the no.of nodes

present in each M.O, symmetry elements & also indicate HOMO-LUMO

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.O, symmetry elements & also indicate HOMO-LUMO

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. CON & DIS Rotation

b. Suprafacial & antarafacial shift

c. HOMO & LUMO 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 PMO method &

indicate under which conditions the reaction is allowed.

32. Discuss the mechanism of [1, 5]-H shift suprafacial using FMO 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

FMO 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

PMO method & indicate under which conditions the reaction is allowed.

35. Explain 2πs+2πs & 2πs+2πa cycloadditions based on FMO approach &

indicate under which conditions the reaction is allowed.

36. Explain 4πa+2πa & 4πs+2πa cycloadditions based on PMO approach &

indicate under which conditions the reaction is allowed.

37. Explain the reaction conditions for the electrocyclic DIS ring closure of

hexatriene to cyclohexadiene based on PMO approach

38. Explain the reaction conditions for the electrocyclic DIS ring closure of

butadiene to cyclobutene based on FMO 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 PMO approach.

b.Write the selection rules of Electrocyclic reactions based on FMO 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 HOMO of the polyenyl radical

b.Using Orbital Symmetry Correlation diagram method, explain [2πs+2πs]

cycloaddition.

8. a. Explain the terms CON & 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:

10. a. Draw the CD for CON 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 CON rotation is allowed thermally or photochemically.

b.[1,5] suprafacial migration of sigma bond is allowed thermally but

photochemically forbidden. Explain by using FMO approach.

12. a. Explain PMO 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 FMO 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 FMO theory &

indicate the reaction is allowed under which conditions.

b. Write the products formed in the below given examples.

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

HOMO in thermal condition.

17. a. Discuss mechanism of DIS type of electrocyclic ring closure of 2E,4E-

hexadiene using aromatic transition state theory and indicate the

stereochemistry of the product

b.Write the Molecular orbitals of pentadienyl cation, and which one is

HOMO in thermal condition.

18. a. What are chelotropic reactions, give two examples.

b. Explain Huckel-Mobius Aromatic and Antiaromatic (PMO) 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 CON type of enclosure of 1,3-butadiene using

FMO 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 FMO theory and

indicate the reaction is allowed under which conditions.

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 FMO 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 PMO method by taking electrocyclic reactions as example

b. Write the woodward-hoffmann selection rules for 4nπ electron system

for CON 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.

26. a. Explain Diels alder reaction using Orbital Correlation diagram method in

which both the components are approaching suprafacially.

b. Write about chelotropic reactions & explain the mechanism by FMO

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 FMO 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

PMO approach

b. Draw the CD for DIS electrocyclic ring closure of hexatriene to

cyclohexadiene

30. a. Draw the CD for CON 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

FMO approach

Unit-3:SYNTHETIC STRATEGIES-I

SECTION- 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 Organic 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

O

CH3

Br

+

CH3

O

a

b

+Cl CH3

O

A

B

OEt

Cl

NO2

a

OEt

Cl

OEt

b

OEt

NO2

OEt

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.

13)Write the synthons and the respective synthestic equivalents for the

disconnections shown in the target molecule.

OH

ab

ab??

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

HO

HO

OH

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

COOH

H2N

III

C H

COOH

H3C

) )

20) Explain the following with suitable example

I)Synthon II) FGI

21) What is regioselectivity? Explain with two examples

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

SECTION- 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

O

O 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 Organic synthesis

11) a) Formulate the retrosynthesis of the following molecules

O

O

O

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.

15) Write the order of synthesis of

COCH3

by retrosynthetic

analysis

16) a)What is convergent synthesis? Device a convergent synthesis for

the following molecule.

Ph

OPh

O

b) Write the retrosynthetic analysis and synthesis of the following.

PhPh

O

17)a) Define and illustrate the following terms

i) Stereoselectivity

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.

CH3

O

19)Using disconnection approach give the best possible retrosynthesis and the

following target molecules

i) Ph O ii) Ph O

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 .

CO2H

O

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.

.

H2N C

O

OEt

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.

OHO

26) Using disconnection approach outline the synthesis of the following target

molecule. Indicate the synthons and synthetic equivalents.

O O

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.

OH

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 iodineanhydrous conditions

?

30 a) Formulate the retrosynthesis of the following molecules

i

0

O ii

CO2H

CO2H

HO2C

HO2C

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

C6H5

OHHO

Unit-4: SYNTHETIC STRATEGIES-II

SECTION- 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

retrosynthesis.

8) Using disconnection approach give the retrosynthesis and synthesis for the

following molecule. O

O 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.

SECTION-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

O

O

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.

OH

OH OH

OH?

?

5) a) write the structures of intermediates in the synthesis of retroneciene

N

COOEt

COOEt

O

NaBH4A

1)Ba(OH)2

2) HClB

BrCH2COOEt

Na2CO3

EtOH

C

D

1NaOEt2NaH

NaBH4

E

1.Ac2O

2.t-BuOK

3. BIBAL-H

N

HO

H

OH

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

O

O

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

N

OH

HHO

b) Write the retrosynthetic analysis and synthesis of the following

O O

9) a)Suggest suitable mechanism in the following conversion.

O

O

HO

O

1) tBuOH,H+

2) LAH,ether ,H2O

3)(AC)2O,pyridine H+

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) Outline the most suitable retrosynthesis and the synthesi for the following

target molecules. Give the synthons and synthetic equivalents involved.

i) ii) RR1R2COH

CO2R

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.

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.