LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

WD 06

B.Sc. DEGREE EXAMINATION – CHEMISTRY

SECOND SEMESTER – April 2009

CH 2504 / 2502 – HYDROCARBONS AND STEREOCHEMISTRY

 

 

 

Date & Time: 23/04/2009 / 1:00 – 4:00 Dept. No.                                                   Max. : 100 Marks

 

 

PART – A

Answer ALL the questions:                                                             (10 x 2 = 20)

 

1. Write the structural formula for the following compounds.
2. 3,3-Dimethyl-1-butene; b) But-2-en-1-ol.
3. Classify the following into +M and –M group

₂ ,   ₂ ,   ,

3. What happends when ethylchloride reacts with sodium metal.
4. What is aromaticity Explain with an example?
5. Specify the E and Z notation to the following compounds.
6. a) b)

 

6. What alkyl halide would yield each of the following pure alkene up on dehydro halogenation by a strong base. a) Isobutylene b) 3-methyl-l-butene.
7. In Fridel-craft’s alkylation of benzene using n-propyl chloride gave only Isopropyl benzene rather than n-propyl benzene. Explain.
8. Indicate which ring you would expect undergo nitration in phenylbenzoate.
9. Write the structure of (i) Cis-4-tert-butylmethyl cyclohexane.                           (ii) cis-1, 2-dimethyl cyclohexane
10. What are polynuclear aromatic compounds? Give two examples.

 

PART – B

Answer any EIGHT questions:                                                                   (8 x 5 = 40)

 

11. Write various possible structural formula of alkanes with molecular formula, C₅H₁₂ and write their IUPAC names.
12. Discuss the different factors affecting the stabilities of carbocation (1^o, 2^o and 3^o)
13. Explain Bayer’s strain theory.
14. How will you prepare cyclopentane using Dieckmann’s Synthesis.
15. What are different conformation of cyclohexane. Draw their structure and explain the stabilities.
16. How is ethylene prepared in the laboratroy? How does it react with
17. i) Bromine water ii) Conc. H₂SO₄ iii) HCl                                                            (2+3)
18. Explain the mechanism of Nitration of benzene.
19. What is tautomerism. Explain mitro-acinitro tautomerism exhibited by Nitroethane.
20. Explain by resonance structure that NO₂ is meta directing, where as –OH group is Ortho-para directing towards electrophillic aromatic substitution.
21. Explain the mechanism of Markownikoff’s Propene.

 

21. i) How will you differentiate 1-butyne from 2-butyne.
22. ii) Explain the mechanism of Hydroboration of propene.
23. Write the structure of the product for the following reaction.
24. Napthalene
25. Napthalene

• 2-butene

1. Nitrobenzene
2. Phenol

PART – C

Answer any FOUR questions:                                                                     (4 x 10 = 40)

 

23. a) Explain the type of hybridisation in the following
24. i) Benzene ii) 1, 3 – buta-diene iii) cyclohexane                       iv) l-butyne.
25. Which is more basic ethylamine or Aniline Explain.
26. a) Explain Hyper conjugation.
27. Arrange the compound in the increasing order of acid strength and Explain.
28. CCl₃ COOH ii) CH₃ COOH,           iii) CH₃ CH₂ CH₂ COOH       iv)CH₂Cl OOH
29. A hydrocarbon ‘A’ adds one mole of hydrogen in the presences of a platinum catalyst to form n-hexane. When A is oxidised vigourously with KMnO₄, a single carboxylic acid containing three carbon atoms is isolated. Give the structure and name of A. Show your reasoning including equation for all reactions.
30. i) Explain 1,2 – and 1,4 – addition of HBr with 1,3-butadiene.
31. Write the mechanism Fridel – Craft’s Acylation
32. i) Predict the product of Bromination of
33. Acetanilide b) cinnamic acid
34. Explain Diel’s Alder reaction taking suitable example.
35. Draw various possible conformation of n-butane explain their stabilities based on energy level diagram?

 

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