LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

AD 14

FIRST SEMESTER – NOV 2006

CH 1806 – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

Date & Time : 28-10-2006/1.00-4.00     Dept. No.                                                       Max. : 100 Marks

 

 

 

PART A

Answer ALL questions.                                                                   (10 ´ 2 = 20 marks)

 

1. What is transition state theory? Mention its importance.
2. What are the various kinetics experiments to study the mechanism of a particular reaction?
3. Classify the rearrangement reactions and give example for each.
4. What is memory effect? Explain with an example.
5. Write a short note on catalytic dehydrogenation.
6. Explain Cram’s rule with a suitable example.
7. Explain why meso-stilbene dichloride on heating with pyridine at 200°C gives no product while dl-isomer gives alkene readily.
8. What is epimerisation? Give an example.
9. Explain Walden inversion with a suitable example.
10. Explain the racemization via cations with a suitable example.

 

 

PART B

Answer any EIGHT questions.                                              (8 ´ 5 = 40 marks)

 

11. How trapping of intermediate, cross-over experiments and isotopic labeling studies help to show that a reaction is intermolecular? Explain with suitable examples. (5)
12. How does the kinetics study in chain and parallel reactions help to design the reaction mechanism? Explain with suitable examples. (5)
13. Explain the mechanism of the following rearrangement reactions. (2 ´ 2½)
14. a) Beckman rearrangement b) Baeyer Villiger rearrangement
15. a) Why secondary amides do not undergo Hoffmann degradation? Give reasons. (2½)
16. b) Explain the mechanism of Claisen rearrangement with suitable example. (2½)
17. Explain the mechanism of NaBH₄ reduction. How is it chemoselective? Explain with an example.                                                                                                    (5)
18. How direct electron transfer can bring in reduction? Explain the mechanism with any two examples.                                                                                                    (5)
19. Predict the Cotton effect by the sign of the most occupied octant in the following compounds:

(i) (+)-trans-1-methyl-2-decalone            (ii) 5a-cholestan-6-one.   Explain.                  (2 ´ 2½)

18. Dehydrobromination of diastereoisomeric a-phenyl-b-bromo-b-benzoylpropionic acids with    hot pyridine give different products.  Explain.
19. Write notes on: a) asymmetric destruction  and  b) asymmetric synthesis
20. ‘The cotton effect curves of (+)-3-methylcyclopentanone in methanol shows only a 24%                 reaction upon addition of acid’.  Explain.
21. Give an example for first order and second order asymmetric transformations. Explain.
22. What are the different methods of resolution of racemic mixture? Explain any two methods.

 

 

PART C

Answer any FOUR questions.                                                          (4 ´ 10 = 40 marks)

 

23. a) How does the kinetics study help to design the reaction mechanism in the following      reactions?                                                                                                    (2 ´ 2½)
24. i) Aldol condensation ii) Benzidine rearrangement
25. b) How stereochemical study and isotopic labeling study help to design a reaction      mechanism as intramolecular? Explain with suitable examples.                                   (5)
26. a) Explain the mechanism of                                                             (2 ´ 2½)
27. i) Fischer Indole synthesis and      ii) Favorskii rearrangement
28. b) Predict the products in the following reactions. Give suitable reasons. (5)

 

25. a) Explain the reductive coupling of carbonyl compounds with any two examples. (5)
26. b) How does specific dehydrogenation in steroids take place? Explain the mechanism with an (5)
27. a) Explain the octant rule with a suitable example.
    b) Predict the Cotton effect by the sign of the most occupied octant in the following     compounds:

(i) 3-bromo-4-methoxycyclohexanone           (ii) 3-methylcyclohexanone

27. Explain the following:
    a)  trans-4-t-butylcyclohexane carboxylic acid is more stronger than cis-isomer.
    b) erythro-3-bromo-2-butanol with HBr gives meso product
    c) Dehydrochlorination of 1,2-diphenyl-1-chloroethane gives trans product fastly but cis     product slowly.
28. a) Explain the following with suitable example.
    a)      Asymmetric destruction
    b)      Bredt’s rule
29. c) Axial haloketone rule
30. Prelog’s rules

 

 

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     LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 26

FIRST SEMESTER – APRIL 2007

CH 1806 – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

 

Date & Time: 27/04/2007 / 1:00 – 4:00         Dept. No.                                                       Max. : 100 Marks

 

 

Part-A

                                                        Answer ALL questions.                     (10 ´ 2 = 20)

1. Suggest a method of trapping the intermediate of a reaction, using suitable example.
2. Define microscopic reversibility with example.
3. What is Arndt-Eistert synthesis?
4. Predict which of the following products would be got in Baeyer Villiger oxidation of cyclohexylmethyl ketone.Why?
5. a) What is the catalyst, reactants and the products in Rosenmund reduction reaction?
   b) What is Corey’s reagent and how is it prepared?
6. Explain axial halo ketone rule with an example.
7. What is epimerisation? Give an example.
8. Explain Prelog’s rule with a suitable example.
9. What are the resolving agents used for the separation of racemic bases? Give the structure of any one.
10. Explain Cram’s rule with an example

 

PART B

Answer any EIGHT questions                               (8 ´ 5 = 40)

11. Give the mechanism of Wolf-Kishner reduction reaction.
12. Predict the product with mechanism.
13. Predict the product of Fischer-Indol synthesis with sutiable evidence.
14. What is memory effect? Explain using a suitable example.
15. What are crossover experiments? How are they helpful in arriving at the mechanism of the reaction?
16. ‘Iodination of aniline is inversely proportional to the square of the iodide concentration’. Explain using suitable mechanism.
17. Explain thermal and cationic racemisation with suitable examples.
18. Explain the conformation of cyclohexane with potential energy diagram.
19. Explain asymmetric synthesis with suitable examples.
20. How are optical rotatory dispersion technique helpful in predicting the configuration of molecules?
21. What atropisomerism?  Explain with a suitable example.
22. Explain the stereoselective synthesis of reserpine.

PART C

Answer any FOUR questions                  (4 ´ 10 = 40)

23. a) Predict the product of the reaction of trialkylborane with carbon monoxide in the presence of ethylene glycol, H₂O and NaOH.
    b)  Give the mechanism of oxidative decarboxylation.
24. Give the mechanism of the following rearrangements
    a) Steven’s b) Beckmann’s                        c) Hofmann’s
25. Explain the following:
    i) Diazotisation of aniline follow third order kinetics.
    ii) The rate law for iodination of acetone depends on the concentration of acetone and the base.  Explain the mechanism using suitable non-kinetic evidence.
26. a) Explain any two methods of resolution of racemic modifications.
27. b) What is optical purity? How will you ascertain it?
28. Assign R or S configuration to the following. Justify your answer
29. a) Explain the stereochemical synthesis of yohimbine.
30. b) Write anote on (i) asymmetric destructions (ii) Second order asymmetric transformations.

 

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GH 26

LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – APRIL 2008

          CH 1806 – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

 

Date : 28-04-08                  Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART – A

Answer ALL questions                         (10 ´ 2 = 20 marks)

 

1. Identify the products obtained when cis- and trans-1,2-dimethyl-1,2-cyclohexanediol are treated with an acid?
2. Explain the formation of the product in the following:
   Ph-NH-N=CH-CH₂-R
3. Is Hofmann rearrangement inter or intramolecular? Explain.
4. What happens when phenyl magnesium iodide is treated with diphenyl ketene? Identify the intermediate and give the mechanism.
5. What happens when ethyl benzene is treated with selenium dioxide? Give its mechanism.
6. Explain why the conductivity of boric acid in (–)2,3-butanediol is more than the meso isomer?
7. Between erythro and threo form of 1-bromo-1,2-diphenylpropane, which will undergo dehydrohalogenation faster in the presence of a base. And why?
8. On what principle cis and trans isomers of 4-t-butyl cyclohexanol is separated by chromatography technique using alumina as the adsorbent?
9. Why neomenthyl chloride reacts faster with NaOEt than menthyl chloride?
10. What are ORD plane curves?

PART – B

 

Answer any EIGHT questions                   ( 8 ´ 5 = 40 marks)

 

11. How would you effect the following conversion? Explain with mechanism.

 

12. Explain with mechanism the formation of product in the following:

 

 

13. ‘The rate of base-catalysed iodination of aniline in the presence of excess iodide ion is inversely proportional to the square of the iodide concentration’. Derive the rate law and explain with mechanism.
14. How is isotopic labeling technique useful in determining the mechanism of a chemical reaction? Explain with two suitable examples.
15. Explain the mechanism of ozonolysis of olefins. Identify the products obtained on subjecting the following compounds in ozonolysis followed by reduction.
    a) 1,3,5-trimethylbenzene                  b) 2,3-dimethyl-2-pentene.
16. How is addition-elimination reaction mechanism useful in identifying the products in oxidation-reduction reactions? Explain with two suitable examples.
17. ‘The solvolysis reactions of 2-phenyl-3-pentyl tosylate and 3-phenyl-2-pentyl tosylate with acetic acid give the same products’. Explain with mechanism.
18. Explain the pyrolysis reaction of xanthates and acetates with suitable examples.
19. Explain Curtin-Hammett principle using the following reaction.

 

 

 

 

 

20. How is the stable conformation of 1,2-dibromocyclohexane classified by dipole moment measurements?
21. Assign R and S notation for the following compounds
22. a)  b)                                c)                                 d)

 

 

 

 

 

 

22. How the major product in an asymmetric induction reaction can be predicted by Cram’s rule and prelog’s with suitable example.

PART – C

Answer any FOUR questions                  ( 4 ´ 10 = 40 marks)

 

23. a) How is the determination of order of a reaction helpful in ascertaining the mechanism of organic chemical reactions? Explain with two suitable examples.
24. b) What are consecutive reactions? Derive the kinetics for benzoin condensation and explain the mechanism.
25. Explain the mechanism of the following rearrangements with suitable examples.
26. a) Baeyer-Villiger rearrangement
27. b) Beckmann rearrangement
28. c) Hofmann rearrangement
29. Explain the following with suitable mechanism in oxidation-reduction reactions.
30. a) Hydrogen atom transfer reaction
31. b) Formation of ester intermediate
32. c) Oxidation of alcohols
33. Discuss the stereochemistry of the following reactions:
34. a) Reaction of cis ans trans 2-aminocyclohexanol with HONO.
35. b) Solvolysis reactions of neomenthyltosylate and menthyl tosylate in acetic acid
36. c) Reaction of erythro-3-bromo-2-butanol with HBr
37. Explain the following
38. a) First order asymmetric transformation
39. b) Walden inversion
40. c) Chemical method of racemisation by cation intermediate formation
41. Discuss in detail the stereo selective synthesis of reserpine.

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

DB 21

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – November 2008

           CH 1806 – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

 

Date : 04-11-08                 Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

Part-A

                                                     Answer ALL questions.                                      (10 ´ 2 = 20)

1. R-CN is prepared by treating RCOO^– with BrCN. Where the carbon in RCN comes from? How?
2. How would you effect the following conversion? Explain with mechanism.
3. What is memory effect in rearrangement? Explain with an example.
4. What happens when phenyl azide is heated with aniline? Explain the formation of the product.
5. Explain the mechanism of ozonolysis of alkenes with an example.
6. What would be the preferred conformer of trans-1,2-dibromocyclohexane? And how its conformation changes with solvent polarity?
7. Explain why the optically active 2-benzoylpropionic acid undergoes racemization when treated with sodium ethoxide in ethanol?
8. Define enantiomeric excess. What is its percentage value for active and racemic products?
9. Solvolysis rate of cis-4-t-butyl cyclohexyl tosylate is greater than that of trans-isomer. Explain.
10. What is atrolactic acid rule? Give one example.

 

Part-B

                                                     Answer any eight questions.                              (8 ´ 5 = 40)

11. Explain the mechanism of Arndt-Eistert synthesis. Mention any one evidence for the mechanism.
12. How do isotopic labeling and stereochemistry help in predicting suitable reaction mechanisms? Give examples.
13. Explain kinetic and thermodynamic controls of a chemical reaction with a suitable examples.
14. ‘Diazotisation of aniline follows II order kinetics in nitrous acid’. Explain the mechanism.
15. How was the mechanism of von-Ritcher rearrangement confirmed? Explain the steps.
16. How would you effect ring cyclisation reaction in Fischer-Indole synthesis? Explain with mechanism.
17. What are the conditions to be fulfilled for a resolution process through diastereomers formation?
18. Why the deamination of (Ph)(Ph’)(OH)C-CH(NH₂)CH₃ does not follow Curtin-Hammet principle? Explain.
19. Discuss the steric course of the acetolysis reaction of 2-phenyl-3-pentyl tosylate &
    3-phenyl-2-pentyl tosylate.
20. Predict the stereochemical change of acetolysis of 3-methoxy-2-bromobutane in the presence of silver acetate in acetic acid.
21. Discuss the conformation analysis of 1,2 & 1,3-disubstituted cyclohexane.
22. Predict the Cotton effect for the following compounds
23. a)                                      b)                                      c)

 

 

Part-C

                                                     Answer any four  questions.                              (4 ´ 10 = 40)

23. a) How does the kinetic study in chain and parallel reactions help to design the reaction mechanism? Explain with suitable examples.
24. b) Explain the mechanism of Favorskii rearrangement. How is it useful in ring contraction reactions?
25. a) Explain the Wagner Meerwein rearrangement reactions. How does neighbouring group help in this rearrangement? How do elimination and substitution reactions compete in the product formation?
26. b) Explain the mechanism of the following rearrangement reactions. (2 ´ 2½)
27. a) Beckman rearrangement        b) Baeyer Villiger rearrangement
28. a) How do amines undergo dehydrogenation? Explain the mechanism.
29. b) Explain Gomberg-Bachmann Pinacol synthesis with a suitable example.
30. c) Explain the mechanism of cannizaro reaction.
31. a) Discuss the optical isomerism of allenes and spiranes.
32. b) Explain the reaction of erythro-3-bromo-2-butanol with HBr
33. Explain the following with example
34. a) Cram’s cyclic model
35. b) Atropisomerism
36. c) Chemical method of racemisation by anion intermediate formation
37. Discuss in detail the stereo selective synthesis of yohimbine.

 

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         LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

WD 49

FOURTH SEMESTER – April 2009

CH 4955 – ORGANIC CHEMICAL TECHNOLOGY

 

 

 

Date & Time: 28/04/2009 / 9:00 – 12:00  Dept. No.                                                 Max. : 100 Marks

 

 

PART-A

Answer ALL questions.                                                                       (10 ´ 2 = 20 marks)

 

1. Define back mixing. What are its advantages and disadvantages?
2. Why sulphonated products are very much useful industrially? Give reasons with example.
3. What are the types of hydrogenating agents?
4. Compare batch and parallel reactors.
5. Narrate the preparation of titanium dioxide.
6. A simple U-tube manometer is filled with mercury (specific gravity = 13.6) and the liquid above the mercury level is carbon tetrachloride (specific gravity = 1.6). The manometer reads 8.30 in. What is the pressure difference over the manometer in inches of water?
7. What is Reynolds number? Give its significances.
8. What is velocity gradient in a laminar flow?
9. Define Couette flow.
10. What is theoretical or equilibrium diagram?

 

 

PART-B

Answer any EIGHT questions.                                                           (8 ´ 5 = 40 marks)

 

11. What are the physical factors that affect chemical process kinetics of chemical reactions? Write a short note on each.
12. How is nitration of 2-methylpentane carried out? What are the products formed? Write the mechanism of the reaction.
13. Explain in detail the workup procedure for sulphonation reaction and its products.
14. How are various types of chlorination reactions performed industrially?
15. What is the need for a research and development unit in industry? Discuss in detail.
16. With the flow diagram explain the manufacture of paint.
17. Describe the pump work in Bernoulli equation.

 

18. Write short notes on impellers.
19. Explain the working principle of bubble cap column with diagram.

 

 

 

20. Explain the following
21. a) energy balance over a flow system
22. b) effect of temperature upon heat of the reaction
23. Describe the various components involved in the fractionating column.
24. What is differential distillation and give its applications?

 

PART-C

Answer any FOUR questions.                                                            (4 ´ 10 = 40 marks)

 

23. a) Explain the effect of back-mixing on the product distribution and holding time in parallel and series reactions.
24. b) How are temperature controlled reactions performed industrially?
25. c) How is spent acid from nitration reaction recycled?
26. a) Explain the method of nitration of hydrocarbons using Schmid nitrator.
27. b) How is phenol manufactured industrially from cumene? Explain in detail.
28. a) Explain the industrial preparation of hydrogenation of vegetable oil.
29. b) What are the functions of quality control unit?
30. a) Derive Barometric equation.
31. b) Give the working principle of continuous gravity decanter.
32. a) Explain the terms Newtonian and non-Newtonian flow.
33. b) Write note on the mechanical energy balance in potential flow.
34. How will you calculate the vapour composition of a mixture using Raoult’s law?

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – NOVEMBER 2010

    CH 1806  – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

 

Date : 30-10-10                 Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART-A                                      

 

Answer all questions             (10 × 2 = 20 marks)

1. What is peroxide effect? Explain with a reaction mechanism.
2. State and explain the principle of microscopic reversibility.
3. Explain the importance of the reaction between neopentyl iodide and aqueous AgNO₃.
4. Complete the following reaction with mechanism.
5. Explain the effect of electron withdrawing and releasing groups in direct electron transfer mechanism with example.
6. Predict the product of the following reaction;

 

7. Why is the following b-ketoacid highly resistant to decarboxylation?
8. Explain Curtin-Hammett principle with an example.
9. How would you resolve optically active alcohols from a racemic mixture?
10. What is epimerization? Give an example.

 

 

 

PART-B

Answer any eight  questions.                      (8 × 5 = 40 marks)

 

11. Give an example for α, β, γ and δ-elimination reaction.
12. State and explain the Hammond postulate to the bromination of n-propane.
13. How will you determine the reaction mechanism of hydrolysis of an ester using isotoping labeling method?
14. Write and explain the Steven’s rearrangement.
15. Predict the product and explain the mechanism of the following reaction.
16. Discuss the Gomberg-Bechmann synthesis.
17. Write the mechanism of the following reaction
18. Identify the stereochemistry of the products obtained when
    a-phenyl-b-bromo-b-benzoyl propionic acid is heated with pyridine.
19. Explain the process of racemisation through cation formation with two suitable examples.
20. Assign R/S configuration to the following:
21. a) b)                                        c)

 

 

21. Explain the stability of various conformers of disubstituted cyclohexanes with energy.
22. State and explain Octant rule. Draw the octants and predict the sign of Cotton effect to the following compounds.
23. a) (+)-3-methylcyclohexanone b) 2-bromocyclohexan-4-one carboxylic acid

 

 

 

PART-C

Answer any four  questions                       (4 × 10 = 40 marks)

 

23. (a) How does crossover experiment is used to determine the reaction mechanism? Explain with example.            (4)

(b) Explain the mechanistic implications of rate law for a diazotization of aniline reaction.                                                                                 (6)

24. (a) What is migratory aptitude? Suggest any two methods to determine the migratory aptitude.   (4)

(b) Give the products of the following                                                  (1+1)

 

(c) How will you convert the following? Explain with mechanism.      (4)

25. (a) Explain the addition-elimination reaction mechanism of a α, β-unsaturated ketone.                                                             (4)

(b) Give any two synthetic applications of selenium dioxide.               (2)

(c) Write the product with mechanism for the following reaction         (4)

26. a) Write the most stable conformations to the following: (6)
    i)                                                ii)                                   iii)

 

1. b) Explain second order asymmetric transformation with a suitable example.

 

 

 

 

27. Explain the following:
28. a) meso-stilbene dichloride possesses a dipole moment 1.27D
29. b) Threo-3-bromo-2butanol with HBr gives dl product.
30. c) Trans-4-tert-butyl cyclohexane carboxylic acid in aqueous DMF is more acidic than cis isomer. (3+3+4)

 

28. a) Explain the axial haloketone rule. What are the uses of this rule?  Explain with an example each.                                                                            (5)
29. b) Explain the steps involved in the stereochemical synthesis of reserpine.(5)

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FOURTH SEMESTER – APRIL 2012

CH 4955 – ORGANIC CHEMICAL TECHNOLOGY

 

 

 

Date : 20-04-2012              Dept. No.                                       Max. : 100 Marks

Time : 1.00 – 4.00

PART-A

Answer ALL questions:                                                                                                   (10 ´ 2 = 20 marks)

1. Mention any two rheological properties of fluids.
2. What is inclined manometer? Give its advantages.
3. Define the following.
4. a) extraction battery b) diffusion battery
5. Give the correlation between different temperature units.
6. What is Couette flow?
7. What are the factors affecting chemical process kinetics?
8. How is the DVS ratio of a mixed acid calculated?
9. What are mild hydrogenating catalysts? Why are they called so?
10. Write all the products obtained when cumene hydrogenperoxide is hydrolysed?
11. How is industrial bulk preparation different from fine chemicals?

 

PART-B

Answer any EIGHT questions:                                                                                        (8 ´ 5 = 40 marks)

11. Explain the total energy balance of steady flow process.
12. Derive barometric equation.
13. Explain the working principle of concurrent leaching experiment.
14. Write short notes on impellers.
15. Discuss about the Hydrostatic equilibrium in a centrifugal field.
16. Explain the various terminologies involved in the material balance diagram in plate column.
17. Write the complete classification of various chemical reactors.
18. Write detailed notes on parallel reactions and how is the product distribution affected due to back mixing?
19. Explain the industrial chlorination of benzene. How are byproducts managed?
20. Classify in detail the oxidizing agents used for industrial preparations.
21. How is moisture control done to maintain proper DVS ratio during the industrial nitration of benzene?
22. Explain the industrial preparation of a Hansa yellow dye.

 

PART-C

Answer any FOUR questions:                                                                                          (4 ´ 10 = 40 marks)

23. a) Derive Bernoulli’s equation of flow of liquid in potential flow.                                     (5)
24. b) How the types of fluid flow identified by Reynolds experiment? (5)
25. a) What is inclined manometer? Give its advantages.                                                 (4)
26. b) Write notes on types of agitators and mixers. (6)
27. a) Derive an expression for the overall material balance of distillation of two component system in a plate column.                                                             (5)
28. b) Explain the working principle of tray dryer.             (5)
29. a) What are complex series reactions? Explain their importance.                         (5)
30. b) How is nitration of benzene done using Biazzi nitrator? (5)
31. a) Compare the reactivity of liquid SO₃ and sulphuric acid towards sulphonation reactions. (4)
32. b) Explain the industrial preparation of penicillin. (6)
33. a) How is industrial scaling up done? (4)
34. b) Write the preparation of blue and red pigments. (6)

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

FIRST SEMESTER – NOVEMBER 2012

CH 1812 / 1806 – ORGANIC REACTION MECHANISM & STEREOCHEMISTRY

 

 

Date : 01/11/2012            Dept. No.                                        Max. : 100 Marks

Time : 1:00 – 4:00

PART – A

Answer ALL questions:                                                                                (10 x 2 = 20)

 

1. Write the mechanism of Chichibabin reaction.
2. What is primary kinetic isotope effect? Explain with suitable example.
3. “Diazotization of aniline follows second order with respect to nitrous acid” Propose a mechanism for this reaction.
4. What is para-Claisen rearrangement? Explain with mechanism.
5. How does indole prepared from phenyl hydrazine?
6. What is Birch reduction?
7. What happens when cyclohexene on ozonolysis?
8. In α, α’-dimethylsuccinic acid, the meso form predominates at equilibrium over the racemic form. Why?
9. State and explain Cram’s rule with suitable example.
10. What is atropisomerism? Give example.

 

PART-B

Answer ANY EIGHT questions:                                                                   (8 x5 = 40)

 

11. Draw the potential energy diagram of thermodynamic and kinetically controlled product formation of a reaction between 1,3-butadiene and HBr.Explain.
12. Explain the microscopic reversibility with suitable example.
13. Explain the following;
14. a) trapping of intermediate      b) isotope labeling study
15. Explain the mechanism of abnormal Claisen rearrangement.
16. How would you convert 1,7,7’-trimethyl bicycle[2,2,1^1-4]heptan-2-ol into 2,2’-dimethyl-3-methylidene bicycle [2,2,1^1-4]heptane?
17. When treated with p-CH₃C₆H₅SO₂Cl in pyridine, the α-benzilmonoximes undergo Beckmann rearrangement with fragmentation. Explain.
18. Explain any one application for each of the following reagents.
19. a) SeO₂ b) OsO₄
20. How does a carboxylic acid undergoes oxidative decarboxylation? Explain.
21. Explain mutarotation with any one example.
22. Give an example for a first order asymmetric transformation reaction and explain.

 

21. Predict the stereochemical change of acetolysis of 3-methoxy-2-bromobutane in the presence of silver acetate in acetic acid.
22. State Brett’s rule and explain the reactivity of bicyclic rings.

 

PART-C

Answer ANY  FOUR questions:                                                                  (4 x10 = 40)

 

23. a) “Radical bromination of isopentane is more selective than chlorination.” Explain with potential energy diagram.
24. b) How does a Raman spectroscopy is used to determine the mechanism of nitration of benzene? Explain.
25. a) Determine the reaction mechanism of base-catalysed iodination of  aniline in presence of excess of iodide ion from its experimental rate data.
26. b) Predict the products to be expected from acid-catalyzed rearrangement of cis- and trans-1,2-dimethylcyclohexane-1,2-diol and sketch mechanism for the formation.
27. a) “The lactones obtained by the Baeyer-Villiger oxidation of camphor and apocamphor contain 25% and 94% of the abnormal product” Why?
28. b) Explain memory effect with suitable example.

 

26. a) Give mechanism for the following conversions.

(i) Methane into methanol using aq.CrO₃

(ii)Acetaldehyde into acetic acid using O₂ and Ag.

1. b) Complete the following with mechanism.

 

27. a) What are the various products obtained on the acetolysis of 3-phenyl-2-pentyl tosylate?
28. b) Explain the process of separation of racemic alcohols with an example.
29. c) Asssign R,S configurations to the following:

 

28. a) State and explain curtin-Hammett principle with suitable example.
29. b) Explain the following with  applications; (i) cotton effect  (ii) axial haloketone rule.

 

 

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