CS MAINS 2014 CHEMISTRY Paper-II


Which one of following ions is. expected to be aromatic? 'Explain the reason. Draw additional resonance structuresLfot:the aromatic ion.
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2-Methylcyclohexanone can be converted to two different enolates by·appropriate choice of reaction conditions. These on further treatment with methyl iodide can yield 6-dimethylcyclohexanone and 2-dimethylcyclohexanone. Account for the formation of these products.

Give the geometry and the hybridization state involved in singlet and triplet carbenes. Predict the product in the following reaction
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How do you account for the fact that Dieckmann cyclization ofdiethyl 3-methylheptariedioate gives a mixture of two p-keto ester products. What are their structures, and why is a mixture formed

Predict and account for the formation of stereoisomers in the following reactions src='./qimages/261-1e.jpg'>

How do you account for the fact that 3-bromo-l-butene and I-bromo-2-butene undergo SNI reaction at the same rate although one is a secondaiy halide and the other is primary

Give two important methods of generation of free radicals and explain why allylic and benzylic radicals are both more stable than non-allylic radicals.

Predict the product and identify the product/s in the following reactions src='./qimages/261-2c.jpg'>

The reaction of 3-butadiene with HCI produces a mixture of products. Write those products. Among the products which one is formed preferentially in the early stages of the reaction? What does this indicate? What will happen to the product mixture. as a function of time

Q. In NGP reactions enhancement of rate and retention of configuration is observed. Explain why. Also predict the productJs in the following reactions with justification.

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Q. Predict and account for the different regioisomers formed in the reactions given below:

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Q. What product would you expect from Hofmann elimination of a cyclic amine such as piperidine Write all the steps involved in the elimination.

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Q.4(a) Diels-Alder reaction of cyclopentadiene with maleic anhydride is much faster than the reaction of cyclopentadiene with cis-2-butene. Account for the same on the basis of HOMO-LUMO energies involved. 10

Q.4(b) Explain the origin of regioselectivities observed in Diels-Alder reaction: Predict the major regioisomer formed in the following reaction

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Q. Suggest suitable experiment/technique to establish the following with suitable example: Detection of suspected intermediate Differentiate between intramolecular and intermolecular mechanisms. 15

Q. Give mechanism involved in Wittig reaction. Comment on the effect of stabilized and non-stabilized ylids on outcome of stereochemistry in the reaction. Predict the product in the following reaction

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Q. Draw the structure of repeating unit of following polymers
Neoprene rubber, Gatta Percha and Polystyrene.
Sketch the synthetic route for monomers of Nylon-6 and Kevlar fibres.

Q. What is cis-trans photoisomerization Give mechanism involved in the isomerizations of alkenes. Predict the equilibrium product in the following reaction
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Q. E1plain why hydroboration-oxidation protocol gives anti-Markonikoff's alcohol from unsymmetrical alkene. Complete the following reaction giving predominant stereoisomer and regioisomer.
src='./qimages/261-5c.jpg'> 10

Q. which of the following two pairs of stereoisomers can be distinguished with the help of coupling constants in PMR spectroscopy?' Account for your choice
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Q. Classify the proteins. Give a note on their 2° and 3° structures. 10

Q. Give major m/e peaks for I-phenyl-I-butanone. Give mechanism involved in the formation of McLafferty rearrangement product for the same. 10
Account for the different carbonyl absorptions C for the following compounds:
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Q. Draw the structures of DNA and RNA with all four bases. 15

Q. Suggest appropriate reagents/conditions, with justification, for the desired chemical transformations shown below
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Q. Assign structure to the compOund with mol. formula C9HlO0 on the basis·of the following
spectral data
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Q. Draw the structure of repeating unit of PVC, PET and SBR.
Sketch the synthetic route for monomers of Nylon-6, 6.

Q. Suggest suitable reagents and provide mechanism for the following chemical conversions
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Q. Predict IH NMR spectra for the above compounds
I-propene
I-phenyl-l-propanone.

Q. Predict the base peaks for the following compounds in mass spectroscopy
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Q. Give mechanism involved' in Norrish type II reaction and predict the products in the following reactions
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Q. Proyide mechanism for the following conversion
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Q. What is condensation polymerization Give structure of repeating units in terylene and show how terylene is obtained. 5

Q. Illustrate the difference between thermoplastics and thermosetts.

Q. Calculate Ymax, for the following compounds
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