This set of Organic Chemistry Problems focuses on “Coordination Polymerisation”.
1. Which of the following is true about coordination polymerisation?
a) radical, coordination, anionic, or cationic polymerization, depending on the type of initiation
b) polymerization that is catalysed by transition metal salts and complexes
c) monomers react by eliminating small molecules like H2O, NH3, CH2O and NaCl in a repetitive manner, Indefinite growth of the polymer occurs at both ends
d) a mixture of more than one (or different) monomeric species is allowed to polymerize
View Answer
Explanation: Coordination polymerisation is a form of polymerization that is catalysed by transition metal salts and complexes. In this addition of monomer to a metal complex take place, followed by propagation is by successive insertion of monomer at the metal, and termination occurs when the metal complex separates from the polymer.
2. Which catalyst is commonly used in coordination chain polymerization?
a) nickel
b) ziegler- Natta catalyst
c) zeolite
d) platinum
View Answer
Explanation: A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes (alpha-olefins).
3. Which of the following is true about homogenous Ziegler Natta polymerisation?
a) This is based on titanium tetrachloride organoaluminium co-catalyst
b) This is based on Kaminsky catalyst
c) This is based on neodymium-based catalyst
d) This is based on organoaluminium co-catalyst
View Answer
Explanation: The Homogenous Ziegler Natta coordination polymerization is done with the help of homogenous catalyst such as the Kaminsky catalyst. Kaminsky catalysts are based on metallocenes of group 4 metals (Ti, Zr, Hf) activated with methylaluminoxane (MAO).
4. Which of the following olefine undergo coordination polymerisation in the presence of Ziegler-Natta catalysts?
a) vinyl chloride
b) vinyl ethers
c) acrylate esters
d) ethylene
View Answer
Explanation: The mixing of TiCl4 with trialkylaluminium complexes produces Ti(III)-containing solids that catalyze the polymerization of ethylene. Many alkenes do not polymerize in the presence of Ziegler-Natta or Kaminsky catalysts. This problem applies to polar olefins such as vinyl chloride, vinyl ethers, and acrylate esters.
5. Which of the following is true about heterogeneous Ziegler Natta polymerisation?
a) This is based on titanium tetrachloride
b) This is based on Kaminsky catalyst
c) This is based on neodymium-based catalyst
d) This is based on titanium tetrachloride organo-aluminium co-catalyst
View Answer
Explanation: Coordination polymerization with heterogeneous Ziegler-Natta catalysts is based on titanium tetrachloride and organoaluminium co-catalyst. The mixing of TiCl4 with trialkylaluminium complexes produces Ti(III)-containing solids that catalyse the polymerization of ethylene and propylene.
6. Homogenous Ziegler Natta coordination polymerization occurs via which mechanism?
a) Cossee–Arlman mechanism
b) Mechanism of free-radical polymerization
c) Cationic polymerization mechanism
d) Anionic polymerization mechanism
View Answer
Explanation: The Cossee–Arlman mechanism is the pathway for the formation of C–C bonds in the polymerization of alkenes. The mechanism features an intermediate coordination complex that contains both the growing polymer chain and the monomer (alkene), these ligands combine within the coordination sphere of the metal to form a polymer chain that is elongated by two carbons.
7. Which catalyst is used for the coordination polymerisation of polybutadiene?
a) titanium tetrachloride organo-aluminium co-catalyst
b) kaminsky catalyst
c) neodymium-based catalyst
d) organo-aluminium co-catalyst
View Answer
Explanation: The salt of neodymium has been widely used in industrial polymerization of 1,3-butadiene. The neodymium catalyst causes high catalytic activity during the polymerization of dienes, however good control has not been achieved with regard to molecular weight and molecular weight distribution.
8. Titanium tetrachloride organoaluminium co-catalyst is used in which of the following polymerisation?
a) Ziegler-Natta polymerization
b) Anionic vinyl polymerization
c) Free-radical polymerization
d) Metathesis polymerization
View Answer
Explanation: Coordination polymerization with heterogeneous Ziegler-Natta catalysts is based on titanium tetrachloride and organo-aluminium co-catalyst. The mixing of TiCl4 with trialkylaluminium complexes produces Ti(III)-containing solids that catalyse the polymerization of ethylene and propylene.
Sanfoundry Global Education & Learning Series – Organic Chemistry.
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