LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

DB 07

   B.Sc. DEGREE EXAMINATION – CHEMISTRY

THIRD SEMESTER – November 2008

CH 3502 / CH 4500 – ORGANIC FUNCTIONAL GROUPS – I

 

 

 

Date : 06-11-08                     Dept. No.                                        Max. : 100 Marks

Time : 9:00 – 12:00

 

PART – A

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

 

1. How is 1-bromo-2-methylpropane prepared from 2-methylpropene?
2. Write one example each for a)S_N1 and b)S_NAr reactions.
3. How are the following distinguished using a characteristic chemical test?

a)benzyl alcohol & ethanol     b)phenol & benzyl alcohol

4. How is benzene converted into p-nitrophenol?
5. Write the IUPAC name for a)anisole b)methyl isopropyl ether.
6. How is methyl isopropyl ether prepared using Williamson’s method?
7. Write one example each for a)Norish type-I reaction and b)Wolf-Kishner reduction.
8. Write equations to explain the preparation of a)propan-1-ol using ethanal.
9. Write IUPAC names for a)oxalic acid and b)cinnamic acid.
10. What is trans-esterification? Write one example.

 

 

PART – B

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

 

11. Explain the difference in stereochemistry between n-butyl iodide and t-butyl iodide during nucleophilic substitution reaction, by writing suitable mechanisms.
12. What happens when ethyl iodide is reacted with: a)alc KOH b)alc AgCN c)sodium phenoxide  d)moist silver oxide  e)sodium acetate?
13. Write a suitable mechanism for hydroboration – oxidation reaction. (3)

Explain how 2-phenylethanol prepared by this method.                                (2)

14. a)Arrange the following in the increasing order of acidity: ethanol, methanol, benzyl alcohol and phenol.             (2)

b)Explain why sodium phenoxide is a weaker base than sodium ethoxide.   (3)

15. How is phenol converted into a) salicylaldehyde b) benzene c)aspirin         (2+1+2)
16. Predict the major product when propene oxide is reacted with a)NaNH₂ / NH₃

b)H₃O⁺                                                                                                           (5)

17. Write a suitable mechanism for Williamson’s synthesis                                  (5)
18. How are the following converted? a)CH₃CH₂OH à CH₃CH=CHCHO

b)CH₃COOH à CH₃COCH₃  c)C₆H₅CHO à C₆H₅CH=CH₂                     (2+1+2)

19. How would you distinguish the following? a)methanol & ethanol b)methanal & benzaldehyde  c)acetophenone & benzaldehyde                                                                    (1+2+2)

 

20. Write a suitable mechanism for Cannizaro reaction. Identify the rate determining step.

(4+1)

21. How is benzaldehyde converted into benzoin? Write equation. (3)

In which case the α-hydrogen is more acidic between ethanal and propanone.  Why? (2)

22. How are the following compounds prepared? a)acetic acid into malonic acid b)phthalic acid from naphthalene  c)propanoic acid into acrylic acid.                                 (2+1+2)

 

 

PART – C

Answer any FOUR questions.                                                                      (4 x 10 =40 mks)

 

23. A)Point out the differences between S_N1 & S_N2 reactions with respect to

a)effect of using a polar solvent  b)kinetics  c)reactivity of alkyl halides.             (6)

B)How is n-propyl bromide prepared from a)propene b)ethyl bromide         (1.5 + 2.5)

24. A)How are the following compounds prepared from ethanol? a)CHI₃ b)ethanoic acid  c)phenyl ethanoate  d)ethyne  e)methanal                                                              (5 x 2 =10)
25. A)How is ethane oxide prepared? (4)

B)Write a suitable mechanism for the reaction:

CH₃CHO + CH₃CH₂CHO à CH₃CHOHCH(CH₃)CHO                 (6)

26. A)Write a note on a)Jablonskii diagram b)use of a cyanohydrin (3+3)

B)Predict the product when alkaline KMnO₄ is reacted with maleic acid and fumaric acid.

(2+2)

27. A)Arrange the following in the increasing order of pKa values:

benzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid and p-nitrobenzoic acid. (4)

B)How are the following prepared from acetyl chloride?  a)ethanal  b)acetophenone

c)acetic anhydride                                                                                                   (6)

28. A)What happens to the acid strength along the homologous series of carboxylic acids?

Explain.                                                                                                           (1+3)

B)Write note on the following: a)Knoevenagel reaction  b)action of heat on α, β and γ-hydroxy acids  c)Use of Zn-Hg / HCl in organic synthesis.                                      (3×2=6)

 

 

 

 

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