CHEMISTRY
Paper II
I Time Allowed: Three Hours I I Ma;-dmum Marks 200 I
INSTRUCTIONS •
Candidates should attempt question nos. 1 and 5
which are compulsory, and any THREE of the
remaining questions, seleCling at least ONE
que.1·tion from each Section.
All questions carry equal marks.
Marks for each part/subpart of a question· are
i;tdicated against each.
Answers must be Written in ENGLISH only.
Assume suitable data, . if considered necessary,
and indicate the same clear(v.
Unless otherwi.l'e indicated, symbols and
notations have their usual meanings.

(Contd.)
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Section
1. Attempt any four of the following 4xl0=40
one of the following chemical species is aromatic Justify with reasoning:.
1.Cycloheptatrienyl radical
2.Cycloheptatrienyl cation
3.Cycloheptatrienyl anion and
4.Cyclopcntadienyl radical 5
(ii)What arc nitrenes ·How is nitrene
generated by thermal decomposition of
acyl azide? 5
identify B in the following reaction and
explain the result by mechanism.
<img src='./qimages/1338-1b1.jpg'>

(ii)The reaction of r-butyl bromide is faster
through SN1/El pathway in the presence
of Ag+ ion. Explain the reason. 5
(c)(i)Identify the major product in the·
following reaction. Justify its regio selectivity.
<img src='./qimages/1338-1c1.jpg'>

Give structure of A and B in the
following sequence and offer mechanistic
explanation for conversion of A to B.
<img src='./qimages/1338-1c2.jpg'>


one of the two cyclobutenes
A and B undergoes ring opening under
thermal conditions under concerted
process Explain while writing structure
of the products.
<img src='./qimages/1338-1d1.jpg'>

Which of the compound In each set given
below reacts more readily in nucleophilic
aromatic substitution with CH3<TNa+ in
CH30H Explain your answer.
<img src='./qimages/1338-1d2.jpg'>

elevation in boiling point of a
aqueous solution of a polymer is
0·0021 K. Calculate the molecular weight
of the polymer.
Given The molal elevation in boiling
point of water is Kb 0·52 k/m.

(ii)Write the major product formed in each
of the following reactions.
1. o-cresol Br2 in CC14
2. m-chlorophenol HN03->low temp
2 products

3. p-cresol Br2 in
4. p-bromophenol CH3COCl ->AlCl3

How do pyrrole aromaticity established based
on the basis of orbital theory 10
(b)Identify the addition products from the
reaction of 1,3-butadiene with HCl at 0°C and
at 30°C. Explain which one of them is kinetic
and thermodynamic. 10

(c)Write the structure of A and B in the following
synthetic scheme. Discuss regiochemistry of A
<img src='./qimages/1338-2c.jpg'>

An organic compound A of MF:C6H12O
forms 2,4-DNP derivative. It does not reduce
Tollen's reagent but undergoes iodoform
reaction. Its mass spectrum has m/2 43 (base peak), 72, 100 (Molecular ion peak,
Deduce its structure. 10

3.(a)A hydrocarbon A of MF: C9H12 absorbs two
moles of hydrogen. On photolysis in methanol
at -20°C A isomerises to B. B absorbs three
moles of hydrogen to form cyclononane. In its
UV spectrum B exhibits lamda max at 290 nm. On
warming to 30°C B isomerises to C whose
structure is given below. Write structure of
A and B and explain each step.
<img src='./qimages/1338-3a.jpg'>

(b)Write the structure of A-D in the following
synthetic sequence and explain the conversion
of B to C with appropriate mechanism.
<img src='./qimages/1338-3b.jpg'>
(c)Write. the structures for A-E in the following
synthetic sequence and explain.
<img src='./qimages/1338-3c.jpg'>

Why the following two alcohols each react
with HCl to _give the same alkyl halide?
<img src='./qimages/1338-3d.jpg'>

4.(a)A mixture of 3-Methoxyaniline, methyl vinyl
ketone were heated in nitrobenzene in presence
of H2SO4 Fe(II)SO4 (cat). Write the
structure of the major product and offer
mechanistic explanation. Indicate the name
reaction. 10
Write structures for B and C in the
following synthetic sequence and give
mechanism for conversion of B to C.
<img src='./qimages/1338-4b.jpg'>

Write the structure of the product formed in
the following reaction and give mechanism.
<img src='./qimages/1338-3c.jpg'>

(d)identify synthetic intermediates A-C and give
mechanism for formation of A.
<img src='./qimages/1338-3d.jpg'>

Section
5.Attempt any four of the following 4x10=40
(a)(i)Starting from benzene and ethylene enumerate
industrial synthesis of polystyrene.
What are silicones Give the method for
their synthesis from chlorosilanes. 5
(b)(i)Explain the salient features of the
structure of zeolites useful for water
softening. 5
Distinguish the following compounds by IR spectroscopy.
<img src='./qimages/1338-5b1.jpg'>

the products of the following
reaction. Propose a suitable mechanism
to account for the product.
<img src='./qimages/1338-5c1.jpg'>
What are the reagents used to effect the
following reaction to proceed to completion
What is the name of this reaction
<img src='./qimages/1338-5c2.jpg'>


Two isomeric ketones A and B MF: C6H10O show following spectral data
<img src='./qimages/1338-5d1.jpg'>

When n-heptane solution of camphor was
irradiated with UV light it isomerizes to
an aldehyde, Write its structure and give
mechanism.
<img src='./qimages/1338-5d2.jpg'>

Explain how to differentiate between
dihydroxy benzenes A-C by 1H decoupled
13C NMR spectroscopy.
<img src='./qimages/1338-5e1.jpg'>

(ii)Differentiate following ketones by mass
spectrometry.
<img src='./qimages/1338-5e2.jpg'>

6.(a)Explain why Grignard reagent, MeMgI, does
not add to 1,3-cyclohexane dione but it adds to
cyclohexanone. 10
(b)Write the structure of the monomer of natural
rubber.Explain why it is elastic. How to
reduce its elastic property by chemical processes
(c)Why docs bromination of cyclohexene with
NBS in CCl4 occur exclusively at allylic
position rather than at one of the other
positions? 10
(d)How to determine the weight average
molecular weight ·of PVC by light scattering
technique 10
7.(a)Write the structure of the intermediate B and
final product C in the following sequence.
C shows strong IR band at 1740
1H NMR spectral signal at 3·8 ppm and
13C NMR spectral signal at 170 ppm. Assign
the spectral data for C.

<img src='./qimages/1338-7a.jpg'>

(b)Direct photolysis of ketone A leads to its
isomer B whereas photolysis in presence of
sensitizer leads to another isomer C. Identify
B and C and explain wilh mechanism.
<img src='./qimages/1338-7b.jpg'>

(c)Photolysis of dimethyl acetylenedicarboxylate
in benzene provides dimethyl 1,3,5,7-cyclo-octatetraenedicarboxylate.
Explain the result by identifying the intermediate. 10

Discuss the nature of bonding and structures of
phosphonitrillic halides. 10

8.(a)Deduce the structures of compounds A and B
based on the following data
A(MF:(C7H7NO3) exhibits strong IR bands at 1530. and 1350 cm-1. A can be
reduced to B (MF C7H9NO3) by reaction
with Sn/HCl B exhibits following signals
in its lH NMR spectrum.
<img src='./qimages/1338-8a.jpg'>

The signal at 3.2 disappears on shaking NMR
solution with D2O 10

(b)Differentiate methyl benzoate and phenyl
acetate by IR and 1H NMR spectroscopy. 10
(c)Show the splitting of the gaseous ion
degeneracy of of the ground state by the
crystal field, spin-orbit coupling and magnetic
field. l0

The compound given below can be
prepared by the addition of HBr to either
of two alkenes. Write the structures of
the two alkenes.
<img src='./qimages/1338-8d1.jpg'>

(ii)What are the products formed if the same
two alkenes each react with DBr? 10