Engineering Chemistry MCQ (Stereo Structure of Polymers)

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Engineering Chemistry MCQ (Stereo Structure of Polymers)

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Stereo Structure of Polymers

1. Which of the following scientists won the noble prize for their work in polymer stereochemistry?
a) Kurt Alder and Richard Abegg
b) Peter Agre and Agricola
c) Zeigler and Natta
d) Friedrich Accum
Answer: c
Explanation: Ziegler and Natta shared the noble prize in 1963 for their work in stereochemistry of polymers.

2. A tactic dyad has a segment of the polymer chain consisting of _________ monomeric units.
a) 5
b) 2
c) 3
d) 4
Answer: b
Explanation: A tactic dyad has a segment of the polymer chain consisting of two
monomeric units. Dyad means two, triad means three.

3. The polymer in which alternate chiral centres have the same configuration is called ____________
a) Syndiotactic
b) Atactic
c) Isotactic
d) Multitactic
Answer: a
Explanation: The polymer in which alternate chiral centres have the same
configuration is called syndiotactic, in which the repeating units have alternating stereo chemical configurations.

4. The tendency for a polymer to adopt crystalline morphology increases with __________ stereo regularity.
a) Decreasing
b) Increasing
c) First increasing then decreasing
d) First decreasing then increasing
Answer: b
Explanation: The tendency for a polymer to adopt crystalline morphology increases
with increasing stereo regularity, regardless of the type of stereochemistry.

5. The configuration of the isotactic dyad is ____________
a) Rectus
b) Racemic
c) Chiral
d) Meso
Answer: d
Explanation: The configuration of the isotactic dyad is meso. Isotactic denotes a
polymer in which all the repeating units have the same stereo chemical configuration.

6. When each chiral centre has the same configuration, the polymer is called ____________
a) Atactic
b) Syndiotactic
c) Isotactic
d) Multitactic
Answer: c
Explanation: When each chiral centre has the same configuration, the polymer is
called isotactic. It denotes a polymer in which all the repeating units have the same stereochemical configuration.

7. Atactic polymer is that in which?
a) Alternate chiral centres have the same configuration
b) Every third chiral centre has the same configuration
c) Each chiral centre has the same configuration
d) A complete random distribution of configuration is there
Answer: d
Explanation: Atactic polymer is that in which a complete random distribution of
configuration is there. Atactic polypropylene has little order in the polymer backbone and is amorphous.

8. A tactic triad has three possible sequences, viz. (i) mm (ii) rr (iii) mr(or rm).
a) True
b) False
Answer: a
Explanation: A tactic triad has three possible sequences, viz. (i) mm (ii) rr (iii) mr(or
rm). An isotactic triad (mm) is made up of two adjacent meso diads, a syndiotactic
triad (rr) consists of two adjacent racemo diads and a heterotactic triad (rm) is
composed of a meso diad adjacent to a racemo diad.