Description
Tutor Marked Assignment
Stereochemistry and Reactive Intermediates (MCH-012)
Course Code: MCH-012
Assignment Code: MCH-012/TMA/2025
Maximum Marks: 100
Note: Attempt all the questions. The marks for each question are indicated against it.
1. Carry out the following conversions as indicated.
a) Fischer form to: i) Staggered and Eclipsed Sawhorse forms and
ii) Staggered and Eclipsed Newman forms
(5)
COOH
COOH
OH H
OH H
b) Flying wedge form to Fischer forms
H OH
HO CH2CH3
i) C
H
Ph
ii) C
OH
COOH
(5)
2. a) Suppose that there is a mixture having a specific rotation of +75o and an
enantiomeric excess of 60%. Find out the enantiomeric composition of the
mixture.
(5)
b) Draw the meso isomers of the following compounds.
CH3
H3
C
Br OH
HO Br
OH
Cl
i) ii)
HO
Cl
(5)
3. a) List the properties of diastereomers. Indicate whether the following are
enantiomers or diastereomers.
and
H
Cl
HO
H3C
Cl
OH
CH3
H
H
Br
H
Br
OH
OH
and
OH
OH i) ii)
(5)
b) How are disubstituted cyclohexanes different from monosubstituted
cyclohexanes with reference to the isomerism? Draw the two chair
conformations for each of the following disubstituted cyclohexanes. Draw also
the cis and trans isomers and indicate the more stable isomer.
(5)
5
i)
cis-Bromo-1-methylcyclohexane
ii) trans-2-Butyl-1-isopropylcyclohexane
iii) cis-4-Ethyl-1-hydroxycyclohexane
4. a) What are the advantages and limitations of method of quasi-racemates? (5)
b) What is pseudoasymmetry? Explain with the help of a suitable example. (5)
5. a) Briefly explain conformationally rigid systems and conformationally mobile
diostereomers giving one example for each. Also correlate the reactivity and the
conformations of these examples.
(5)
b) What are left- and right- circularly polarised lights? Draw suitable diagrams for
them.
(5)
6. a) Give any two applications of ORD and CD. (5)
b) What is the principle of microscopic reversibility? Explain taking the example of
an addition-elimination reaction or a nucleophilic substitution reaction.
(5)
7. a) Select the resonance stabilised cation and give reason for your answer. (5)
+
H
+ + O
+
C +
, , , ,
b) Write the product formed and give the mechanism.
(i) ? HCl
(ii) ?
I
AgNO2
(5)
8. a) Does a carbanion behave as an acid or a base? Explain the stability of
carbanion on the basis of this behaviour?
(5)
b) Arrange the following anions in the decreasing order of stability. (5)
CH2
NO2
CH2
NO2
CH2
NO2
CH2
, , ,
6
9. a) Predict the product and write the mechanism. (5)
4 CCl
hv NBS CH CH CH CH CH 3 2 3
b) Arrange the following radicals in their increase order of stability and give
the reason of your answer.
C ) H (C , H C ) H (C , C ) (CH H, C ) (CH 3 5 6 2 5 6 3 2 3
(5)
10. Write the products formed in each of the following and give the mechanism. (10)
i) +CHBr3
NaOH, Aq. AgNO3
ii)
+NaN3, H3O+ ,
C
O
Cl
iii)
+
LDA, Base
Br
OMe
HC(COOMe)2
(LDA, lithium diisopropyl amide)
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