Download CHE 6 2008

CHE-06
Assignment Booklet
Bachelor’s Degree Programme (B.Sc.)
Organic Reaction Mechanism
(Valid for July 01, 2008 to June 30, 2009)
School of Sciences
Indira Gandhi National Open University
New Delhi, 110068
Dear Student,
We hope, you are familiar with the system of evaluation to be followed for the Bachelor's Degree
Programme. At this stage you may probably like to re-read the section on assignments in the Programme
Guide that was sent to you after your enrolment. A weightage of 30 percent, as you are aware, has been
earmarked for continuous evaluation, which would consist of one tutor-marked assignment for this
course. This assignment is based on Blocks 1 to 4.
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Tutor Marked Assignment
Organic Reaction Mechanism
Course Code: CHE-06
Assignment Code; CHE-06/TMA/2008-9
Maximum Marks: 100
Answer all the questions given below.
Q.1 a)
b)
Q.2 a)
b)
Explain the following terms with suitable examples.
i)
Carbanion
ii)
Nucleophile
iii) Electrophilic substitution
iv) α-Elimination
(6)
Differentiate between:
i)
The enthalpy driven and the entropy driven reactions
ii)
Primary isotope effect and secondary isotope effect
(4)
Name the process which is used to describe the mechanism of SN2 reaction. Why is
this name given? Explain the mechanism taking an example.
(5)
Which mechanism would be followed by the following during a nucleophilic
substitution reaction and why?
(5)
i) Neopentylbromide
ii) 1-Chloro-1,2-diphenylethane
Q.3 a)
b)
c)
Give the molecular orbital description of aromaticity taking a suitable example.
(5)
Does the addition of HBr to propenenitrile follow Markownikoff’s rule? Give reason
to your answer.
(2½)
What were the finding of Kharasch and Mayo regarding addition reaction of alkenes?
Explain with suitable example.
(2½)
Q.4. a)
Explain the following:
i)
Aromatic ketones are less reactive than aliphatic ketones
ii)
Hydration of hexafluoropropanone is faster than propanone
iii) Importance of reaction of carbonyl compound with sodium hydrogen sulphite
b)
How would you prepare ketal from hemiketal? Give its mechanism and importance
of this reaction.
(2)
What are the differences between E2 and ElcB reactions? Explain with suitable
example.
(3)
What is oxidation state? Calculate oxidation state of both the carbon atoms of
CH3COOH.
(2)
c)
d)
Q.5 Give the mechanism of the following:
i)
Wolf-Kishner Reduction
ii)
Hofmann Elimination
iii) Perkin Condensation
iv) Wittig Reaction
(3)
(10)
Q.6 a)
Write the product(s) and give the suitable mechanisms of the following reactions:
(5)
i)
CHCl3/ 50 % KOH
Cat. Bu4 NCl
ii)
b)
Q.7 a)
b)
c)
PH
H
H
Ph
CH2 I2 , Zn/Cu couple
How can you detect the formation of a free radical as an intermediate during a free
radical reaction?
(5)
Explain why does 2-bromo-3- methyl-anisol not react while amide ion in liquid
ammonia?
(2)
Explain why do the free radical additions of HCl and HI to alkenes normally not take
place?
(5)
Write steps involved in following transformations:
(3)
NHC6H5
N3
(i)
Aniline
N
OH
OH
CHO
CHCl3
(ii)
KOH
C6 H5 Li
(iii)
NHCH3
NHCH3
Q.8 a)
Give the main product and the mechanism of the following reaction to explain the
formation of the predicted product:
NO2
CH3
C
C
OH
OH
H+
(3)
b)
Name the two rearrangement reactions used in the preparation of a homologue with
one carbon atom less. Write the mechanism of any one of them.
(4)
Why are [1,5] sigmatropic shifts quite common in comparison to [1,3] sigmatopic
shifts? Explain.
(3)
What are positive the ways, a singlet state of a molecule dissipate its excess energy?
(5)
By taking a suitable example, explain the role of protection groups in the organic
synthesis.
(5)
Give the preparation of a primary alcohol, a secondary alcohol, and a tertiary alcohol
using suitable starting materials and Grignard reagents.
(3)
b)
How will you prepare cyclobutane carboxylic acid using malonic ester.
(2)
c)
How are industrial processes different from lab process for the preparation of a
industrial important organic compound?
(5)
c)
Q.9 a)
b)
Q.10 a)