North Maharashtra University 2009 B.Sc Chemistry Stereo-isomerism - Question Paper

stability.
e. What is G.I.? provide necessary & sufficient condition for G.I.
f. Which of the subsequent compound exhibit G.I. & why?
CH3-CH=C (CH3)2 & CH3-CH=CH-CH3
g. explain the saw horse & Newman projection formulas for representation of
Conformations with suitable example.
h. Draw the Conformation of n-propane.

ques. for four marks.
1) ans the subsequent.
a. Draw the chair & boat Conformation of cyclohexane showing axial &
equatorial hydrogen atoms.
b. What is Conformational isomerism? discuss with the example of ethane.
c. discuss in brief, how optical rotation is measured?
d. discuss the terms enantiomers & diastereomers with example.
e. discuss in brief about the Elements of symmetry with example.
f. discuss tetrahedral carbon.
g. Write a note on specific rotation.
h. discuss the chiral centre & chirality.
i. Causes of optical activity.
j. Draw Newman projection formulas for chair & boat Conformation.
k. discuss in brief Angle strain & non-bonded interactions.
l. What do you maen by flipping of a ring? discuss with suitable example of
methyl cyclohexane.
m. discuss in brief G.I. of oximes with suitable examples.
n. Draw the structures of Equatorial & axial methyl cyclohexane & comment
on their stabilities.
o. Explain, why the conformers of n-butane can not be isolated at room temp.
p. What is G.I.? discuss cis & trans isomerism with suitable example.
2) organize the subsequent groups in decreasing order of priority & justify.
a. –NH2, -C=N, -NH-CH3, -NO2
b. –CH2OH, -CH2SH, -CH2Cl, -CH2F
c. –CHO, -CH3, -CH2-C=N, -CH2-NH2
d. –F, -Cl, -Br, -I
e. –I, -Cl, -SO3H, -H

ques. for six marks.
1) discuss the method to measure the optical activity of an organic compound.
2) describe the term “specific rotation”. provide the formula for specific rotation.
discuss the meaning of terms involved in it. What will be the effect on
observed rotation, if the length of the polarimeter tube is doubled.
3) Define, (a) plane polarized light (b) Chiral centre (c) Enantiomers.
discuss working of polarimeter.
4) What is optical activity? elaborate the causes for a molecule to be optically
active? Illustrate with suitable example.
5) State & discuss “sequence rules” provided by cahn, Ingold & Prelog.
6) What is meant by “Absolute configuration”? provide the sequence rules for priority
determination.
7) explain the method or steps involved in determining R/S configuration by using
Fischer projection formula with suitable example. (Don’t explain the sequence rule.)
8) Draw the conformations of n-butane. compute the potentional energy of every.
Comment on their stabilities.
9) explain the conformation of methyl cyclohexane & Comment on their stabilities.
10) explain the conformational isomers in n-butane using energy profile diagram.
11) explain the conformational isomers in ethane using energy profile diagram.
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12) Draw the different conformations of cyclohexane. Comment on their stabilities
using energy profile diagram.
13) Draw the chair & boat conformation of cyclohexane. Draw their Newman
projection formula. Comment on their stabilities.
14) In case of G.I, discuss cis-trans & E-Z nomenclature system with suitable
examples.
15) discuss in brief.
a) Optical isomerism.
b) Conformational isomerism.
c) Geometrical isomerism.

Earning:   Approval pending.