This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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.
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