General methods of preparation and mechanism of polymerisation Questions in English

(D) Propene $(C_3H_6)$ contains a double bond $(CH_3-CH=CH_2)$ and can undergo addition polymerization to form polypropylene.
Saturated compounds like ethyl chloride,ethanol,and benzene do not typically act as monomers for addition polymerization.

(A) Ziegler-Natta catalyst is a mixture of $TiCl_4$ and $(C_2H_5)_3Al$ used in the synthesis of stereoregular polymers.

(A) . Polystyrene is a chain growth polymer. Chain growth polymers involve a series of reactions,each of which consumes a reactive particle and produces another similar one. The reactive particles may be free radicals or ions (cation or anion) to which monomers are added by a chain reaction. This is a characteristic reaction of alkenes and conjugated dienes,or indeed of all kinds of compounds that contain a $C=C$ double bond. The provided image illustrates the synthesis of polystyrene from benzene via ethylbenzene and styrene.

(A) The polymerization of tetrafluoroethene $(CF_2 = CF_2)$ leads to the formation of polytetrafluoroethene,commonly known as Teflon.
The reaction is: $nCF_2 = CF_2 \to -(CF_2 - CF_2)_n-$ (Teflon).

(D) Condensation polymerization involves the repeated condensation reaction between two different bi-functional or tri-functional monomeric units,usually accompanied by the elimination of small molecules like $H_2O$,$HCl$,or $NH_3$.
Nylon-$66$ is a polyamide formed by the condensation polymerization of hexamethylenediamine $(H_2N(CH_2)_6NH_2)$ and adipic acid $(HOOC(CH_2)_4COOH)$ with the elimination of water molecules.
Teflon,rubber,and styrene are prepared by addition polymerization.

(C) $Nylon-66$ is a polyamide formed by the condensation polymerization of $Adipic \ acid$ $(HOOC-(CH_2)_4-COOH)$ and $Hexamethylene \ diamine$ $(NH_2-(CH_2)_6-NH_2)$.

(C) Neoprene is a synthetic rubber obtained by the free-radical polymerization of chloroprene ($2$-chloro$-1,3-$butadiene).
The chemical formula for chloroprene is $CH_2 = C(Cl) - CH = CH_2$.
Therefore,the correct monomer is $CH_2 = C(Cl) - CH = CH_2$.

(C) Bakelite is formed by the condensation polymerization of phenol and formaldehyde.
During this process,small molecules like water are eliminated,which is characteristic of condensation polymers.

(C) Neoprene is a synthetic rubber formed by the free radical polymerization of chloroprene ($2$-chloro-$1,3$-butadiene).
The chemical reaction is:
$n(CH_2=C(Cl)-CH=CH_2) \xrightarrow{\text{polymerization}} (-CH_2-C(Cl)=CH-CH_2-)_n$
Thus,the monomer of neoprene is chloroprene.

(C) $PMMA$ stands for Polymethyl methacrylate.
It is a synthetic polymer formed by the polymerization of the monomer methyl methacrylate $(CH_2=C(CH_3)COOCH_3)$.

(A) Chain-growth polymerization involves the addition of monomers containing double or triple bonds (like alkenes) to form polymers without the loss of any small molecules.
$Teflon$ (polytetrafluoroethylene) is formed by the addition polymerization of tetrafluoroethylene $(CF_2=CF_2)$,which is a chain-growth process.
$Nylon-6$,$Nylon-6, 6$,and $Bakelite$ are condensation polymers formed by the loss of small molecules like $H_2O$ or $HCl$.

(D) $Bakelite$ is a thermosetting polymer formed by the condensation polymerization of $Phenol$ and $Formaldehyde$ in the presence of an acid or base catalyst.
The reaction involves the formation of $o-$ and $p-$hydroxymethylphenol derivatives,which further cross-link to form the rigid $Bakelite$ structure.

(B) Polypropylene is formed by the polymerization of propylene $(CH_3-CH=CH_2)$.
Since the monomer contains a double bond and the polymerization process involves the addition of monomer units without the loss of any small molecules,it is classified as an addition polymer.
Therefore,the correct description is $Propylene, \text{addition polymer}$.

(C) Step-growth polymerization involves the reaction of bifunctional or multifunctional monomers,typically involving the loss of small molecules like $H_2O$ or $HCl$. $Nylon$ (e.g.,$Nylon-6,6$) is formed by condensation polymerization,which is a type of step-growth polymerization. $Polyethylene$,$Polyisoprene$,and $Polyacrylonitrile$ are examples of chain-growth polymers.

(D) Condensation polymerization involves the repeated condensation reaction between two different bi-functional or tri-functional monomeric units,often with the elimination of small molecules like $H_2O$,$HCl$,or $NH_3$.
Nylon-$66$ is prepared by the condensation polymerization of hexamethylenediamine $(H_2N(CH_2)_6NH_2)$ and adipic acid $(HOOC(CH_2)_4COOH)$.
Teflon,rubber,and styrene are formed via addition polymerization.

(C) The Ziegler-Natta polymerization of ethylene to produce high-density polyethylene is typically carried out at a temperature range of $50\,^oC$ to $80\,^oC$ under low pressure using a catalyst like $TiCl_4$ and $(C_2H_5)_3Al$.

(C) Alkyd resins are a type of polyester resin formed by the polycondensation of a polybasic acid (such as phthalic acid) and a polyhydric alcohol (such as glycerol or glycol). In the context of standard chemistry curriculum,the reaction between a dibasic acid and a polyhydric alcohol like $Glycerol$ is the classic method for producing alkyd resins.

(A) Caprolactam is heated with water at high temperature $(533-543 \ K)$ to undergo ring-opening polymerization.
This process leads to the formation of Nylon-$6$.
It is called Nylon-$6$ because the monomer,caprolactam,contains $6$ carbon atoms.

(A) Bakelite is a thermosetting polymer formed by the condensation polymerization of phenol and formaldehyde $(HCHO)$.
The reaction involves the formation of ortho- and para-hydroxybenzyl alcohol derivatives,which further cross-link to form the rigid structure of Bakelite.

(D) Polymers are formed by the process of polymerization,which involves the repeated joining of monomer molecules to form long-chain macromolecules. This can occur via addition polymerization or condensation polymerization. Therefore,the most accurate description among the given options is the joining of monomer molecules.

(C) $AlCl_3$ is a Lewis acid,which acts as an initiator by generating a carbocation in cationic polymerization.

(B) Condensation polymerization involves the reaction between two bifunctional monomers with the elimination of small molecules like $H_2O$,$HCl$,or $NH_3$.
Nylon-$66$ is a polyamide formed by the condensation reaction between hexamethylenediamine $(H_2N(CH_2)_6NH_2)$ and adipic acid $(HOOC(CH_2)_4COOH)$.
Styrene,Teflon,and Rubber are formed by addition polymerization.

(A) The $Ziegler-Natta$ catalyst is a mixture of $TiCl_4$ and $Al(C_2H_5)_3$ (triethylaluminium). It is widely used in the industrial polymerization of olefins like ethylene and propylene to produce high-density polyethylene and polypropylene.

(A) Chain-growth polymerization involves a series of reactions where each step adds a monomer unit to the growing chain.
This mechanism is characteristic of alkenes and compounds containing $C=C$ double bonds,such as styrene.
Polystyrene is formed via the free-radical polymerization of styrene,which is a type of chain-growth polymerization.
Proteins,starch,and nucleic acids are natural polymers formed via step-growth (condensation) polymerization.

(C) Lactide is a cyclic dimer of lactic acid $(CH_3CH(OH)COOH)$.
When lactide is heated in the presence of a catalyst like zinc chloride $(ZnCl_2)$,it undergoes ring-opening polymerization.
This process results in the formation of polylactic acid $(PLA)$,which is a biodegradable linear polyester.
Therefore,the correct option is $C$.

(D) The given structure is Caprolactam.
Caprolactam undergoes ring-opening polymerization when heated with water at high temperatures to form Nylon-$6$.
Therefore,the correct option is $D$.

(B) $PVC$ stands for Polyvinyl chloride.
It is formed by the addition polymerization of vinyl chloride monomer,which has the chemical formula $CH_2 = CH-Cl$.
The reaction is: $n(CH_2 = CH-Cl) \rightarrow -[CH_2-CH(Cl)]_n-$.
Therefore,the correct monomer is vinyl chloride.

(C) The process of forming a polymer from monomers is known as polymerization. In the initiation step of chain-growth polymerization,the monomer is typically activated by an initiator (such as a free radical,cation,or anion). For example,in cationic polymerization,a proton $(H^+)$ or a Lewis acid acts as an initiator to convert the monomer into a reactive monomer ion (carbocation),which then starts the chain propagation. Therefore,the initiation step involves the conversion of the monomer into a reactive species.

(C) Natural rubber is a linear polymer of isoprene ($2-$methyl-$1, 3-$butadiene).
The polymerization reaction is:
$n \ CH_2=C(CH_3)-CH=CH_2 \xrightarrow{\text{polymerization}} [ -CH_2-C(CH_3)=CH-CH_2 -]_n$
Thus,it is a polymer of $2-$methyl-$1, 3-$butadiene.

(A) Neoprene is a synthetic rubber obtained by the free radical polymerization of chloroprene ($2$-chloro-$1,3$-butadiene). The reaction is represented as: $n CH_2=C(Cl)-CH=CH_2 \rightarrow [-CH_2-C(Cl)=CH-CH_2-]_n$.

(D) $Nylon-6$ is prepared by heating caprolactam with water at a high temperature $(533-543 \ K)$.
The reaction involves the ring-opening polymerization of caprolactam.
Therefore,the correct raw material is caprolactam.

(A) The Ziegler-Natta catalyst is a mixture of titanium tetrachloride $(TiCl_4)$ and triethylaluminum $((C_2H_5)_3Al)$.
This catalyst is used for the polymerization of ethylene to produce high-density polyethylene $(HDPE)$ under low pressure conditions.

(D) Bakelite is a thermosetting polymer formed by the condensation polymerization of phenol and formaldehyde in the presence of an acid or base catalyst. The reaction involves the formation of ortho and para-hydroxybenzyl alcohol derivatives,which further cross-link to form the rigid structure of Bakelite.

(B) The condensation polymerization of hexamethylenediamine $(H_2N(CH_2)_6NH_2)$ and adipic acid $(HOOC(CH_2)_4COOH)$ results in the formation of Nylon-$66$.
This is a polyamide polymer formed by the elimination of water molecules during the reaction.

(D) When $Phenol$ reacts with $Methanal$ $(HCHO)$,it undergoes condensation polymerization to form $Bakelite$,which is a well-known thermosetting polymer.

(D) Cationic polymerization is initiated by electrophilic species or Lewis acids.
$AlCl_3$ is a strong Lewis acid that can accept a lone pair of electrons to generate a carbocation,which acts as the initiator for the polymerization process.
$BuLi$ is an initiator for anionic polymerization.
$LiAlH_4$ is a reducing agent.
$HNO_3$ is a strong acid but not typically used as an initiator for cationic polymerization compared to Lewis acids like $AlCl_3$.

(D) $PVC$ stands for Polyvinyl chloride.
It is formed by the free radical addition polymerization of vinyl chloride $(CH_2=CHCl)$,which is also known as $1-$chloroethene.
The reaction is: $n(CH_2=CHCl) \rightarrow -[CH_2-CHCl]_n-$.
Therefore,the monomer is $1-$chloroethene.

(B) Bakelite is a thermosetting polymer formed by the condensation polymerization of phenol and formaldehyde $(HCHO)$ in the presence of an acid or base catalyst.
This reaction involves the formation of ortho and para-hydroxybenzyl alcohol derivatives,which further cross-link to form the rigid structure of Bakelite.

(B) Natural rubber is obtained by the addition polymerization of isoprene ($2$-methyl-$1,3$-butadiene).

(D) Chain-growth polymers are typically formed by addition polymerization of unsaturated monomers like alkenes or their derivatives.
Among the given options,Teflon (polytetrafluoroethylene) is formed by the addition polymerization of tetrafluoroethene $(CF_2=CF_2)$,which is a classic example of a chain-growth polymer.
Nylon-$66$,Bakelite,and Terylene are examples of step-growth (condensation) polymers.

(B) The $Ziegler-Natta$ catalyst,which is a mixture of $TiCl_4$ and $(C_2H_5)_3Al$,is specifically used in the polymerization of ethene to produce $High-density \text{ } polyethylene$ $(HDPE)$.
This process occurs at low pressure and temperature,resulting in a linear polymer chain with high density.

(B) Chain-growth polymerization typically involves the addition of monomers containing double bonds,such as alkenes or their derivatives. $Polystyrene$ is formed by the chain-growth polymerization of $styrene$ $(C_6H_5CH=CH_2)$.
Nucleic acids,proteins,and starch are natural polymers formed through condensation polymerization processes.

(C) Neoprene is a synthetic rubber formed by the free-radical polymerization of chloroprene ($2$-chloro$-1,3-$butadiene).
The chemical formula for chloroprene is $CH_2 = C(Cl) - CH = CH_2$.
Therefore,the correct monomer is $CH_2 = C(Cl) - CH = CH_2$.

(B) Glyptal is a polyester resin formed by the condensation polymerization of ethylene glycol $(HO-CH_2-CH_2-OH)$ and phthalic acid $(C_6H_4(COOH)_2)$.
The reaction involves the elimination of water molecules to form the polymer chain.

(A) The Ziegler-Natta catalyst is a mixture of $TiCl_4$ and $(C_2H_5)_3Al$.
It is widely known for its stereospecific nature,which allows for the production of polymers with specific spatial arrangements,such as isotactic polypropylene.

(B) $Nylon-6,6$ is a polyamide formed by the condensation polymerization of two monomers: hexamethylenediamine and adipic acid.
Therefore,adipic acid is one of the essential raw materials used in its synthesis.

(A) The given polymer is polyisobutylene,which is formed by the polymerization of isobutylene $(2-methylpropene)$.
The structure of the monomer is $CH_2=C(CH_3)_2$.

(A) Bakelite is a thermosetting polymer formed by the condensation polymerization of $Phenol$ and $Formaldehyde$ in the presence of an acid or base catalyst. The reaction involves the formation of ortho- and para-hydroxybenzyl alcohol derivatives,which further cross-link to form the rigid structure of Bakelite.

(B) The process by which monomers are converted into polymers is known as $Polymerization$. In this process,small repeating units called monomers combine to form a long-chain macromolecule called a polymer.

(B) The Ziegler-Natta catalyst is a mixture of triethylaluminium $(Al(C_2H_5)_3)$ and titanium tetrachloride $(TiCl_4)$.
It is widely used in the polymerization of alkenes.