LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034

M.Sc. DEGREE EXAMINATION – CHEMISTRY

LM 30

SECOND SEMESTER – APRIL 2006

                                     CH 2809 – CHEMISTRY OF MAIN GROUP ELEMENTS

 

 

Date & Time : 21-04-2006/FORENOON     Dept. No.                                                       Max. : 100 Marks

Part-A

Answer all questions. Each question carries two marks

1. Both Li and Mg can be used to remove N₂ from other gases. Rationalize.
2. What are electrides? Cite an example.
3. Europium is frequently found in nature in group II minerals. Comment.
4. Compounds of alkaline earth metal ions are colorless, but [Be(bpy)(C₂H₅)₂] is bright red in color. Account for this observation.
5. What are pyrazaboles? Cite an example.
6. Cite the cyclohexane chair conformational analogue of phosphinoborane.
7. What are silanes? How do they act as a strong reducing agents for halogens?
8. What is ZSM-5 catalyst? Mention any two applications.
9. What is the basic unit of silica present in pyroxene mineral? Draw its structure.
10. Mention the general trend observed in the hydrolysis of interhalogen compounds.

Part-B

Answer eight questions. Each question carries five marks

11. Explain the structure of B₅H₉ using PSEPT theory.
12. Give an account of the preparation, properties, and structure of C₂B₁₀H₁₂.
13. Write brief notes on (a) silylamines and (b) inorganic rubber.
14. Explain the role of zeolites as molecular sieves.

15a.  Explain the principle involved in the qualitative estimation of CO by using I₂O₅.

1. Complete the following reactions: I₂O₅ + H₂S  ?; I₂O₅ + HCl  ?

I₂O₅ + F₂BF₃   ?

16. Explain the synthesis of linear phosphazenes and their reactivity toward amines, alkoxides, aryloxides, and organometallic reagents.
17. Give an account of hexagonal and cubic boron nitrides and their analogy toward graphite and diamond.
18. Give a brief account of natutrally occurring azamacrocycles.
19. Explain the chlorinating and oxidising reactions of any two oxides of chlorine.
20. Give an account of the chemistry of phosphorus compounds with P-P double bonds.
21. Give an account of the synthesis of aluminium alkyls and their synthetic importance. Comment upon the structures of aluminium alkyls and aluminium aryls.
22. How is phosphorus sulfides prepared? Depict their cyclic structures.

Part-C

Answer four  questions. Each question carries ten marks

23. Discuss the bonding in boranes. How can this be extended to cover higher boranes?

24a.  Explain the polyhedral rearrangements of closo-carboranes.                             (5)

1. Explain the preparation, properties, and structure of borazine.                         (5)

25a.  Give a brief account of the chemistry of oxohalogen fluorides.                       (7)

1. Write a note on heteropoly blues.                                                                      (3)

26a.  Explain the special equipments and fundamental techniques employed

in the synthesis of main group nonmetal compounds.                                       (6)

1. Explain the use of hexamethyldisilazane as a silylating agent for organic and inorganic compounds with examples. (4)

27a.  Give an account of naturally occurring ionophores and their interaction with the alkali and alkaline earth metal ions.                                                                    (6)

1. Explain the mechanism of ion transport across  cell membranes.                      (4)

28a.  Explain the synthesis, reactivity, and structural aspects of rings and cages involving

Si-Si multiple bonding.                                                                                      (6)

1. Give an account of heterocyclic inorganic ring systems involving Si-O and N-S bondings.                                                                                                       (4)

 

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