CS CHEMISTRY Paper II

Identify the compound from each of the following pairs, which exhibits aromatic character

(b)Enumerate the reasons for different rates of acetolysis for the following compounds: 10

Name the following reaction and give suitable reagent and mechanism 10

Design a suitable experiment to establish the presence of possible intermediate in the following reaction

Identify the non-isolable intermediate.

(e)Account for the stereochemical outcome in the following reaction by proposing Appropriate, transition state


Q2 2-methylcyclohexanone gives different enolates under kinetic and thermodynamic conditions. While 2-tetralone gives only one (same) enolate under kinetic and thermodynamic conditions. Predict the structures of enolates in each case and account for the same.

Which of the carbo-cations will be more stable in each of the following pairs Give reasons 10

Addition of hydrogen iodide to 3,3-dimethyl- 1-butene yields mixture of 3-iodo-2,2-dimethylbutane and 2-iodo-2,3-dimethylbutane. Offer a mechanism to account for the formation of the products. 15

Identify the reaction and predict the product/s in the following transformations: 15

3 Briefly explain the important methods of generation of carbenes. Explain what are singlet and triplet carbenes. Predict the product/s in the reaction of cis-2-butene with singlet and triplet carbenes. 10

(b)Predict the products and offer the mechanisms for the following chemical transformations: 10

Write the products expected in the reactions shown below. Sketch the mechanisms involved in each case. 10

Write the mechanism involved in the formation' of the following compound by Fischer Indole protocol: „ 10

Account for the stereoselectivity and propose a suitable mechanism for. the following reaction:


Explain with the help of FMO approach, why stereocliemical outcome for 1,5-suprafacial carbon migration and 1,5-antarafacial carbon migration are different. 10

What frontier molecular orbitals are involved in the reaction of Z)-2,4-hexadiene via thermal and photochemical pathways Account for the formation of the different stereoisomeric products. 15

Prove the existence of intramolecular mechanism, when' allyl phenyl ether on heating yields o-allyl phenol. 10

Predict the products and give the mechanisms involved in the, following chemical transformations 15

Write the mechanism of radical polymerization of ethylene leading to branching in the resultant polymer. 10

Predict the major product and explain the origin of the regioselectivity and stereoselectivity observed in the following hydroboration-oxidation reaction: 10

Show Norrish type-II fragmentation for the following compound 10

Briefly explain why C 0 bond stretch frequency occurs at 1740 cm-1 for the carbonyl compound of an aliphatic ester and at 1850 cm-1 for the carbonyl group of acid chloride. 10

Distinguish between the following compounds using proton NMR spectra: 10
1-bromopropane and 2-bromopropane Propanal and propanone

6 Given below are two isomeric compounds with molecular formula C5 H10 O. Predict the base peaks for each of the following:

Show McLafferty fragmentation peak wherever apphcable. 10

An unknown compound, C9H10O2, did not dissolve in aqueous NaOH.
The IR spectrum exhibited strong absorption at 1730 cm-1. The NMR
spectrum had signals at 6 7*2 (multiplet), 4*1 (quartet) and 1-3 (triplet).

Elucidate the structure of the unknown compound. 10

What are the factors responsible for the stability of the double helix
structures of DNA Show the structures of hydrogen bonding between
complementary bases between two DNA strands. 15

Give the mechanism for reduction of a ketone by L1AIH4 and predict the
products in the following reactions 15

Give the mechanisms involved in the epoxidation of an alkene and
1 Baeyer Villiger oxidation of a ketone using MCPBA. 10

What is the advantage of anionic polymerization process in the
formation of polystyrene Enumerate the steps involved in the
polymerization of styrene using butyl lithium as an initiator, 10

Draw the possible structures for the compounds that meet the following descriptions: 10
.
C2HgO; one singlet
C3H7CI; one doublet and one septet
• C4H8CI2O; two triplets
C4H3O2; one singlet, one triplet and one quartet

Complete the following reactions and suggest a suitable reaction
mechanism for each 20

Q8. Predict the McLafferty rearrangement ion peak for the following
compound: 10

Suggest the product and offer the mechanism in the following reaction 10
0
Propose the mechanism for the following chemical conversion

Give the structures of all the bases which occur in both RNA and DNA.
Also; give the structures of the bases which occur in RNA alone or in
DNA alone.

One of the five compounds shown below was analysed by
1 IR spectroscopy. Peaks were observed at 1639 cm*1 (weak) and 1714 cm-1
(strong). There was no signal between 3100 cm-1 to 3500 cm-1. Which
compound was analysed
10