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22550

I IIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIII

III Semester

B.Sc.Ed./M.Sc.Ed.

(RIE Scheme) Chemistry Chemistry

..Organic Time:

Examination,

April/May

2012

-I Max. Marks:

3 Hours Instruction:

60

Your answers should be brief and specific.

1) a) How do you account for the following ?

6

,

i) Phenols are more acidic than alcohols.

.

ii) p-nitrophenol is a stronger acid than m-nitrophenol iii) Acetic acid is weaker acid than formic acid. b) Write short notes on :

6

i) Free radicals ii) Carbocations iii) Carbenes. OR 2) a) Explain hyperconjugation

4

with suitable examples.

b) What are carbanions ? Discuss the stability of carbanbns with suitable examples.

4

c) Use curly arrows and draw resonance

4

structures

for the following

:

:t; i)

jj)

CH3 -CH

= CH -C

EJ;) H -CH3

.c -NH2

CH3

II o

~~ iv)

f'

,

~

c.H2-

:OH

~ P. T.O.

~

22550

II

IIIIIIIIIIIIIIIIImillIIIIIIIIIIIII

.2-

3) a) Assign R/S configuration

4

to the following :

~ i)

c.LL --T~

oH

ii)

~

013

iii)

~H

b) Convert the following Fischer projections sawhorse and flying wedge formula :

H-

4

:=E

~'1

~3

in to eclipsed forms of Newman,

°'r\-\1

-0\--\

i)

ii)

H.

-OH

tt-

e"{ ...::-HL (.) \-\

.'rl ." c) Account for the following : i) A meso compound

4

is optically inactive.

ii) The anti conformation conformation.

of n-butane

is more stable than fully eclipsed

OR 4) a) Write the structures of all possible stereoisomers of tartaric acid and comment on their optical active property. b) Assign E/Z configuration

Ho, i) ~~~C

'B-y

""

~ "H

to the following compounds ~ ii)

"F

4

OH

C-J2r(J"}i "c=c:r

iv) H/L--=-c--(

, '-. H / e-.--= 4'1'-

~c...,

e.L

iii)

fis

:

4

J:1c./

'd

a

c) Write a brief note on conformations of n-butane and cyclohexane

4

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I IIIIII IIIII IIIII 11'11 IIIIIIIIIIIII

22550

-3-

III. 5) a) Write short notes on :

6

i) Baeyer's strain theory and its limitations. ii) Diels-Alder reaction " iii) Corey- House synthesis. b) Explain the mechanism

of electrophilic

addition and free radical addition to

alkene with suitable examples.

6

OR 6) a) How do you effect the following conversions

t

?

6

i) Diethyl adipate to cyclopentane ii)

iii)

1-bromobutane

to Butan-2-o1

Propyne to But-2-ynoic

acid.

b) What is peroxide effect ? Why is it observed only in case of HBr and not with HF, HCI or HI ?

3

c) An alkene on reductive ozonolysis gives one mole of glyoxal and two moles of acetaldehyde. IV

Deduce the structure of alkene.

3

7) a) How do you carryout any two of the following conversions

?

4

i) benzene to p-bromonitrobenzene

.

ii) benzene to m-nitrobenzoic acid iii) p-xylene to 2-chloroterephthalic acid b) Discuss the mechanism of nitration and sulfonation reactions of benzene. c) Arrange the following compounds towards electrophilic

substitution

in the increasing

i) cfl

ii)

r3J o~-Cc:J-1..>

iv) . -,

iii)~~

order of their reactivity

reaction and give reasons.

0--

.cb

4

4

22550

-4-

I IIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIII

8) a) Write short notes on any three of the following:

.{

, , {f:o

9

i) Aromaticity ii) Energy profile diagram for halogenation iii)

Friedel Crafts acylation reaction

iv)

Birch reduction.

of benzene

b) Discuss the limitations of Friedel Crafts alkylation giving suitable examples.

v

9) a) Discuss

and compare

the mechanism

. of SN1 and SN2 reaction

3

of

haloalkanes.

8

b) How do you synthesise the following compounds ?

4

i) Freon ii) Chloretone. OR 10) a) Giving atleast two evidences for formation of benzene intermediate, discuss the elimination -addition mechanism for nucleophilic aromatic substitution reactions. b) Explain why

8 4

i) reactivity of halogenated hydrocarbons towards nucleophilic substitution reactions follows the order allyl chloride > chloroaleane > vinyl chloride. ii) the order of reactivity of haloalkanes

towards E1 reactions is

3° > 2° > 1°.

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