LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 05

SECOND SEMESTER – APRIL 2007

CH 2500 – ORGANIC CHEMISTRY – I

 

 

Date & Time: 20/04/2007 / 1:00 – 4:00        Dept. No.                                                Max. : 100 Marks

 

 

PART – A

 

Answer ALL the questions                                   (10 x 2 = 20)

 

1. Classify the following groups into +I and –I groups: i) CH₃ ii) NH₂ iii) NO₂ iv) Cl
2. Give the differences between mesomeric effect and inductive effect.
3. Define torsional strain and torsional energy.
4. Give the eclipsed and staggered conformations of n-butane.
5. Give the IUPAC names and the structures of the products formed by the reaction of 1-pentyne with one mole of HBr and a peroxide.
6. What is Markownikoff rule? Explain with an example.
7. Why is acetylene acidic?
8. What is Diels-Alder addition reaction?
9. Differentiate between enantiomers and diastereomers.
10. Assign R & S notation to the following compounds:

 

PART – B

Answer any Eight questions                                                        (8 x 5 = 20)

 

11. Distinguish between a) absolute and relative configuration b) meso and racemic forms
12. Draw the Fischer-projection formulae for all the possible stereoisomers of 2,3-dichlorobutane and specify as R or S configurations to the asymmetric carbon.
13. How is 1,3-butadien prepared? Give the reactions of 1,3-butadiene with a) maleic anhydride     b) HBr.
14. Explain the mechanism of halogenation of alkane.
15. How will you prepare the following compounds from acetylene:
16. a) acetaldehyde              b) ethyne         c) vinyl chloride
17. Write short notes on i)Wurtz synthesis ii) Corey House synthesis.
18. How will you prepare the following:
19.             i)  n-propanol from propene    (ii) Glycol from ethylene.

 

18. Explain the mechanism of markownikoff and antimarkownikoff addition of propene.
19. Write short notes on a)hydroboration reaction b) addition polymerization reaction
20. Explain the mode of hybridization of carbon in methane, ethylene and acetylene.
21. Explain cis and trans addition with an example.
22. Write down the structural formulae of the olefin from which the following products are obtained on ozonolysis:
23.                     a) cyclopentanone and acetone   b) ethylmethyl ketone and propanaldehyde

 

PART – C

 

Answer any FOUR questions                                                (4 X 10 = 40)

 

23. a) Explain why aliphatic amines are more basic than aromatic amines.

b)Explain the various factors affecting the stability of primary, secondary,                                                     tertiary and methyl carbonium ions

24. Explain the rate of halogenation of alkanes and the factors affecting the rate of the reaction.
25. Explain the 1,4- and 1,2- addition reactions of butadiene in detail.
26. Give the mechanism of the following reactions: a) dehydration of alcohols b) dehydrohalogenation c) peroxide effect d) alkylation of alkene.
27. Bromination of an organic compound(A) of formula C₆H₁₂ yields C₆H₁₂Br₂. On reduction of the compound gives 2-methylpentane. On oxidation it yields a mixture of acetic acid and isobutyric acids. Assign the structural formula to the organic compound. Express the above reaction by chemical equation and give the IUPAC names of A and other products.
28. a) Discuss the conformational analysis of 1,2-dichloroethane with potential energy diagram. b) Give the E or Z notation to the following compounds:

 

 

 

 

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LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

B.Sc.

LM 11

DEGREE EXAMINATION –CHEMISTRY

FOURTH SEMESTER – APRIL 2007

CH 4500 – ORGANIC CHEMISTRY – II

 

 

Date & Time: 21/04/2007 / 9:00 – 12:00          Dept. No.                                                     Max. : 100 Marks

 

 

 

PART-A                                      

Answer ALL questions.                                                                                  (10 ´ 2 = 20)

1. ‘cyclopropane is more reactive than cyclohexane’.  Explain.
2. How will you prepare a vicinal dihalide from an alkene?
3. Why are lower member of alcohols soluble in water but not the higher members?
4. K_a of CH₃COOH, ClCH₂COOH, Cl₂CHCOOH and CCl₃COOH are 1.75 ´10^-5,
   136 ´10^-5, 5530 ´10^-5 and 23,200 ´10^-5 respectively. Provide a suitable explanation.
5. What is the stereochemistry of the products obtained on the addition of bromine on

maleic acid?

6. How will you synthesise ethylbenzene from acetophenone?
7. How will you distinguish between benzaldehyde and acetophenone?
8. Arrange the following series of compounds in order of increasing acid strength. Give reasons for the order you select.

Benzoic acid, p-ethylbenzoic acid, p-nitrobenzoic acid, o-,p-dinitrobenzoic acid.

9. What is Kolbe reaction?
10. Write any one example for diazo coupling reaction.

 

PART-B                                      

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

11. Write the mechanism for the following reaction

CH₃-CH₂-CH=CH₂   ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

12. How will you prepare 4-methyl pentanoic acid using diethyl malonate?
13. Explain Baeyer’s strain theory of cycloalkanes.
14. a) Write the mechanism for the action hydroiodic acid on ethyl methyl ether? (3)
15. b) What is the action of ethyl iodide on sodium phenoxide? (2)
16. Complete the following reactions.
17. a) Acrylic acid     +     HBr        ¾¾®
18. b) Neopentane     +      Cl₂
19. c)   Bromoethane   +      C₆H₆
20. d) Propanol
21. e) 2 – bromobutane
22. How would you distinguish between primary, secondary and tertiary alcohols by Victor-Meyer’s method?
23. Give the mechanism of Friedal-Craft’s acylation of benzene.
24. Write a note on: (a) Cannizaro reaction (b) Perkin reaction
25. Write any three synthetic applications of acetoacetic ester.
26. What happens when benzamide is treated with bromine in KOH solution? Explain the mechanism.
27. Write a note on: Reimer-Tiemann reaction.
28. Give the product and write the mechanism.

C₆H₅COCH₂CH₃ ??

 

 

PART-C

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

 

23. a) Explain the mechanism of the following reaction and discuss the

stereochemistry of the product formed.                                                           (6)

CH₃Br    +    KOH      ¾®     CH₃OH   +   KBr

1. b) Discuss the effect of polarity of the solvent on the rate of S_N1 and S_N2 reactions.           (4)
2. a) Explain the stability of various conformations of cyclohexane with a potential

energy diagram.                                                                                                  (6)

1. b) Explain the factors affecting the stability of conformations.                           (4)
2. a) How will you prepare the following alcohols using a Grignard reagent? (6)

(i) n-butyl alcohol    (ii) tert-butyl alcohol      (iii) sec-butylalcohol

1. b) How will you distinguish CH₃OH and C₂H₅OH using a simple chemical test.(4)
2. a) Discuss the molecular orbital structure of Benzene. (5)
3. b) Write a note  on: Benzoin condensation                                                           (5)
4. a) How will you synthesise sulphanilamide from aniline? Give its importance.  (5)
5. b)  How will you synthesise m-nitrophenol from nitrobenzene?                          (5)
6. a). How will you convert phenol into:

(i)  benzene  (ii) anisole   (iii) 2,4,6-tribromophenol.                                 (2+2+2)

1. b) What is Claisen rearrangement? Explain the p-migration mechanism of
   2,6-dimethyl allyl phenyl ether.                                                                    (4)

 

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