General methods of preparation and mechanism of polymerisation Questions in English

(C) Terylene,also known as $Dacron$,is a polyester fiber.
It is prepared by the condensation polymerization of Ethane-$1, 2$-diol (ethylene glycol) and Benzene-$1, 4$-dicarboxylic acid (terephthalic acid).
The reaction involves the elimination of water molecules to form an ester linkage between the monomers.

(A) The reaction involves the free radical polymerization of styrene $(C_6H_5CH=CH_2)$ in the presence of dibenzoyl peroxide as an initiator.
During polymerization,the double bond of the vinyl group breaks,and the monomer units link together to form a long chain.
The structure of the repeating unit in polystyrene is $[-CH_2-CH(C_6H_5)-]_n$.
Comparing this with the given options,structure $I$ represents the correct polymer structure.

(D) The correct answer is $(d)$.
In free radical polymerisation,the monomer must be capable of forming a stable radical intermediate. Compounds $(I)$ (styrene),$(II)$ (acrylonitrile),and $(III)$ (methyl acrylate) contain electron-withdrawing groups attached to the double bond,which stabilize the radical formed during the propagation step through resonance.
Compound $(IV)$,methyl vinyl ether $(CH_2=CH-OCH_3)$,has an electron-donating methoxy group. The oxygen atom donates electron density into the double bond,making it electron-rich. This destabilizes the formation of a radical intermediate in a free radical mechanism,as radical polymerization typically requires electron-deficient alkenes to stabilize the radical center.

(A) Cationic polymerization proceeds via the formation of a carbocation intermediate. The rate of polymerization is directly proportional to the stability of the carbocation formed.
The stability of the resulting carbocations is as follows:
$I: CH_3O_2C-CH_2-CH_2^+$ (destabilized by $-I$ and $-M$ effects of the ester group)
$II: Cl-CH_2-CH_2^+$ (destabilized by $-I$ effect of $Cl$)
$III: CH_3-CH_2-CH_2^+$ (stabilized by $+I$ effect of the methyl group)
$IV: Ph-CH_2-CH_2^+$ (highly stabilized by resonance with the phenyl ring)
Thus,the stability order is $I < II < III < IV$. Consequently,the reactivity order for cationic polymerization is $I < II < III < IV$.

(D) Caprolactam is heated with water at a high temperature $(533-543 \ K)$ to undergo ring-opening polymerization.
This process results in the formation of the polyamide known as Nylon $6$.
The reaction is represented as:
Caprolactam $\xrightarrow{H_2O, \Delta} [CO-(CH_2)_5-NH]_n$ (Nylon $6$).

(D) Ethene undergoes addition polymerisation to form high density polythene in the presence of a catalyst such as triethylaluminium $(Al(C_2H_5)_3)$ and titanium tetrachloride $(TiCl_4)$,which is known as the Ziegler-Natta catalyst.
This process occurs at a temperature of $333 \ K$ to $343 \ K$ and under a pressure of $6-7 \ \text{atm}$.
High density polythene consists of linear molecules and is closely packed,which results in high density and high melting point.

(A) Neoprene is a synthetic rubber formed by the free radical polymerization of chloroprene $(2\text{-chloro-}1,3\text{-butadiene})$. The chemical reaction is as follows:
$nCH_2=C(Cl)-CH=CH_2 \xrightarrow{\text{Polymerization}} [CH_2-C(Cl)=CH-CH_2]_n$
Thus,the monomer required for the production of neoprene is chloroprene,which corresponds to option $A$.

(A) To form a condensation polymer with adipic acid $(HOOC-(CH_2)_4-COOH)$,we need a diamine $(NH_2-(CH_2)_n-NH_2)$.
$1$. If $X = CONH_2$,the reaction with $Br_2 / NaOH$ (Hofmann bromamide degradation) gives $NH_2-(CH_2)_4-NH_2$. This is a diamine,which reacts with adipic acid to form a polyamide (Nylon-$6$,$4$).
$2$. If $X = CN$,the reaction with $H_2 / Ni / \text{heat}$ (catalytic hydrogenation) gives $NH_2-(CH_2)_6-NH_2$. This is a diamine,which reacts with adipic acid to form a polyamide (Nylon-$6$,$6$).
Both $(C)$ and $(D)$ result in the formation of a diamine,which can undergo condensation polymerization with the given dicarboxylic acid. Thus,the correct pairs are $(C)$ and $(D)$.

(D) The monomers used in the preparation of Dextron are lactic acid and glycolic acid.
$n CH_3-CH(OH)-COOH + n HO-CH_2-COOH \rightarrow -[O-CH(CH_3)-CO-O-CH_2-CO]_n- + n H_2O$
Thus,Dextron is a copolymer of lactic acid and glycolic acid.

(C) Dexon is a biodegradable polymer prepared from the monomers lactic acid and glycolic acid.
It is a copolymer formed by the condensation polymerization of these two hydroxy acids,resulting in the formation of ester linkages.
The reaction is as follows:
$nCH_3-CH(OH)-COOH + nHO-CH_2-COOH \rightarrow [-O-CH(CH_3)-CO-O-CH_2-CO-]_n + nH_2O$

(D) Addition polymerisation involves the repeated addition of monomer molecules possessing double or triple bonds to form a polymer without the loss of any small molecules.
$Teflon$ (polytetrafluoroethylene) is formed by the addition polymerisation of tetrafluoroethene $(CF_2=CF_2)$.
$Nylon$ $6$,$Terylene$,and $Nylon$ $6, 6$ are condensation polymers formed by the elimination of small molecules like $H_2O$ or $CH_3OH$.

(B) Polyacrylonitrile is prepared by the free radical polymerization of acrylonitrile $(CH_2=CH-CN)$.
Free radical polymerization requires a radical initiator,such as a peroxide (e.g.,benzoyl peroxide),to initiate the chain reaction.
Nylon $6,6$ and Terylene are prepared by condensation polymerization,while Bakelite is prepared by step-growth polymerization involving phenol and formaldehyde.

(B) Condensation polymerization involves the repeated condensation reaction between two different bi-functional or tri-functional monomeric units,usually with the elimination of small molecules like $H_2O$,$HCl$,or $NH_3$.
$Nylon \ 6, 6$ is formed by the condensation of hexamethylenediamine $(H_2N(CH_2)_6NH_2)$ and adipic acid $(HOOC(CH_2)_4COOH)$.
Polythene,Polyacrylonitrile,and Teflon are all examples of addition polymers formed by the polymerization of unsaturated monomers.

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

(B) Ring-opening polymerization involves the addition of cyclic monomers to a growing polymer chain without the elimination of small molecules like $H_2O$ or $CH_3OH$.
Nylon-$6$ is a well-known example of a polymer formed by the ring-opening polymerization of $\varepsilon$-caprolactam.
The structure of Nylon-$6$ is $[NH-(CH_2)_5-CO]_n$.
Therefore,the correct option is $B$.

(D) Thermocol is a trade name for expanded polystyrene $(EPS)$.
It is prepared by the polymerization of the monomer $Styrene$ $(C_6H_5CH=CH_2)$.
Therefore,the correct monomer used for the preparation of thermocol is $Styrene$.

(C) The polymerization of tetrafluoroethylene to produce polytetrafluoroethylene $(PTFE)$ is carried out by heating or exposing tetrafluoroethylene to a free radical initiator such as ammonium persulphate or hydrogen peroxide under high pressure.

(A) $\varepsilon$-Caprolactam does not undergo vinyl polymerization.
It undergoes ring-opening polymerization to form Nylon-$6$.

(C) Polyacrylonitrile $(PAN)$ is a polymer formed by the addition polymerization of acrylonitrile monomer.
The chemical formula for acrylonitrile is $CH_2=CH-CN$.
Therefore,the correct monomer is $H_2C=CH-CN$.

(C) Thermocol is a trade name for expanded polystyrene $(EPS)$.
It is produced by the polymerization of the monomer $Styrene$ $(C_6H_5CH=CH_2)$.
Therefore,the correct answer is $Styrene$.

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

(A) Nylon $2-$ nylon $6$ is a polyamide copolymer.
It is formed by the condensation polymerization of two monomers:
$1$. Glycine $(H_2N-CH_2-COOH)$
$2$. $\epsilon$-amino caproic acid $(H_2N-(CH_2)_5-COOH)$
Therefore,the correct option is $A$.

(C) Nylon $6,6$ is prepared by the condensation polymerization of hexamethylenediamine and adipic acid.
In the first step,these two monomers react to form a $1:1$ salt known as nylon salt.
The reaction is: $HOOC(CH_2)_4COOH + H_2N(CH_2)_6NH_2 \rightarrow [^-OOC(CH_2)_4COO^-][^+H_3N(CH_2)_6NH_3^+]$ (Nylon salt).

(C) $Dacron$ (also known as $Terylene$) is a polyester fiber. It is prepared by the condensation polymerization of ethylene glycol $(HO-CH_2-CH_2-OH)$ and terephthalic acid ($benzene-1,4-dicarboxylic \ acid$,$HOOC-C_6H_4-COOH$). The reaction involves the elimination of water molecules to form an ester linkage.

(B) Buna-$S$ is a synthetic rubber formed by the copolymerization of $1,3-$butadiene and styrene in the presence of a sodium catalyst.
The reaction is as follows:
$n(CH_2=CH-CH=CH_2) + n(C_6H_5CH=CH_2) \xrightarrow{Na} -[CH_2-CH=CH-CH_2-CH(C_6H_5)-CH_2]_n-$

(C) Nylon $6$ is prepared by heating caprolactam with water at a high temperature $(533-543 \ K)$.
During this process,the amide bond in the cyclic caprolactam ring breaks,leading to ring opening polymerization.
The reaction is as follows:
$\epsilon$-Caprolactam ($n$ molecules) $\xrightarrow{H_2O, 533-543 \ K} [NH-(CH_2)_5-CO]_n$ (Nylon $6$).

(A) The given polymer is $-(CH_2-CH(CONH_2))_n-$,which is polyacrylamide.
Polyacrylamide is formed by the addition polymerization of the monomer acrylamide $(CH_2=CH-CONH_2)$.
Therefore,the correct monomer is acrylamide.

(B) Dacron (also known as Terylene) is a polyester formed by the condensation polymerization of ethylene glycol (a dihydric alcohol) and terephthalic acid (an aromatic dicarboxylic acid) in the presence of a zinc acetate-antimony trioxide catalyst at $420-460 \ K$.

(B) The monomer $HO-CH_2-CH_2-OH$ is known as ethylene glycol.
It is used in the preparation of Dacron (also known as Terylene).
Dacron is a polyester formed by the condensation polymerization of ethylene glycol and terephthalic acid in the presence of a zinc acetate-antimony trioxide catalyst at $420-460 \ K$.
The reaction is: $n \ HO-CH_2-CH_2-OH + n \ HOOC-C_6H_4-COOH \rightarrow [-O-CH_2-CH_2-O-CO-C_6H_4-CO-]_n + 2n \ H_2O$.

(D) The monomer used in the preparation of Teflon is tetrafluoroethylene,$(CF_2=CF_2)$.
Polymerization of tetrafluoroethylene under high pressure in the presence of a peroxide or persulphate catalyst yields Teflon,which is $(CF_2-CF_2)_n$.

(C) Novolac is a linear polymer formed by the condensation polymerization of $Phenol$ and $Formaldehyde$ in the presence of an acid catalyst.
It is a type of phenol-formaldehyde resin.

(A) Neoprene is a synthetic rubber prepared by the free radical polymerization of chloroprene ($2$-chloro$-1,3-$butadiene).
The chemical reaction is:
$n(CH_2=C(Cl)-CH=CH_2) \rightarrow (-CH_2-C(Cl)=CH-CH_2-)_n$
Thus,the monomer is chloroprene,which has the structure $CH_2=C(Cl)-CH=CH_2$.

(A) Nylon $6,6$ is a polyamide formed by the condensation polymerization of two monomers: hexamethylenediamine $(H_2N-(CH_2)_6-NH_2)$ and adipic acid $(HOOC-(CH_2)_4-COOH)$.
During the reaction,a molecule of water is eliminated for each amide linkage formed,resulting in the polymer chain.

(A) Teflon is prepared by the polymerization of tetrafluoroethylene $(CF_2=CF_2)$.
The chemical reaction is:
$nCF_2=CF_2 \xrightarrow[(NH_4)_2S_2O_8]{\text{Heat, pressure}} -(CF_2-CF_2)_n-$
Here,$C_2F_4$ is the monomeric unit.

(B) Nylon $6, 6$ is a condensation polymer formed by the reaction between hexamethylenediamine and adipic acid.
Condensation polymerization does not require a free radical initiator like peroxide,whereas $LDP$,Polyacrylonitrile,and Teflon are addition polymers that typically require a peroxide initiator for free radical polymerization.

(D) Polyacrylonitrile $(PAN)$,also known as Orlon or Acrilan,is a polymer formed by the addition polymerization of acrylonitrile monomer.
The chemical reaction is as follows:
$nCH_2=CHCN \xrightarrow{\text{peroxide catalyst or } KNH_2/NH_3(l)} -[CH_2-CH(CN)]_n-$
Thus,the monomer is acrylonitrile,which has the formula $CH_2=CHCN$.

(B) $PAN$ stands for Polyacrylonitrile. It is a polymer formed by the addition polymerization of acrylonitrile monomer. The chemical formula for acrylonitrile is $CH_2=CH-CN$. Therefore,the correct monomer is $CH_2=CH-CN$.

(C) The monomer shown in the image is acrylamide,which has the chemical formula $CH_2=CH-CONH_2$.
Upon polymerization,the double bond breaks,and the monomer units link together to form a long chain polymer known as $Polyacrylamide$.
The reaction can be represented as:
$n(CH_2=CH-CONH_2) \rightarrow (-CH_2-CH(CONH_2)-)_n$
Thus,the correct polymer is $Polyacrylamide$.

(C) $Nylon-6$ is prepared by heating caprolactam with water at a high temperature.
In this process,the ring of caprolactam opens to form aminocaproic acid,which then undergoes polymerization to form $Nylon-6$.
The reaction is as follows:
$\text{Caprolactam}$ $\xrightarrow{H_2O, \text{Heat}} H_2N-(CH_2)_5-COOH$ $\xrightarrow{\text{Heat}} (-NH-(CH_2)_5-CO-)_n \text{ (Nylon-6)}$

(A) $Polyvinyl$ $chloride$ $(PVC)$ is a polymer formed by the polymerization of $vinyl$ $chloride$ monomer. The chemical formula for $vinyl$ $chloride$ is $CH_2=CHCl$. The polymerization reaction is as follows:
$n(CH_2=CHCl) \xrightarrow{\text{catalyst}} -[CH_2-CHCl]_n-$

(D) The polymer obtained from $\varepsilon$-caprolactam is Nylon-$6$.
When $\varepsilon$-caprolactam is heated with water at high temperature,it undergoes ring-opening polymerization to form Nylon-$6$.

(C) cyclic amide is also known as a lactam.
$\varepsilon$-caprolactam is a seven-membered cyclic amide that is used as a monomer for the preparation of Nylon-$6$.
Therefore,the correct option is $C$.

(A) $HDP$ stands for high-density polyethylene. It is a linear polymer with high density due to close packing.
$HDP$ is obtained by the polymerization of ethene in the presence of a Ziegler-Natta catalyst,which is a combination of triethylaluminium and titanium tetrachloride,at a temperature of $333 \ K$ to $343 \ K$ and a pressure of $6-7 \ atm$.

(B) Teflon is a polymer formed by the polymerization of tetrafluoroethylene $(CF_2=CF_2)$.
The reaction is carried out by heating tetrafluoroethylene with a free radical or persulphate catalyst at high pressure.
The chemical equation is: $nCF_2=CF_2 \xrightarrow[(NH_4)_2S_2O_8]{\text{Heat, pressure}} -[CF_2-CF_2]_n-$
Thus,the monomer used is tetrafluoroethylene.

(B) $Terylene$ (also known as $Dacron$) is a polyester fiber.
It is prepared by the condensation polymerization of $Ethylene \ glycol$ $(HO-CH_2-CH_2-OH)$ and $Terephthalic \ acid$ $(HOOC-C_6H_4-COOH)$.
The reaction is as follows:
$n(HO-CH_2-CH_2-OH) + n(HOOC-C_6H_4-COOH) \rightarrow -[O-CH_2-CH_2-O-CO-C_6H_4-CO]_n- + 2nH_2O$
Therefore,the correct monomers are $Ethylene \ glycol$ and $Terephthalic \ acid$.

(C) Neoprene is a synthetic rubber produced by the free radical polymerization of chloroprene.
The chemical name for chloroprene is $2-$chlorobuta$-1,3-$diene.
The reaction is as follows:
$n \ CH_2=C(Cl)-CH=CH_2 \xrightarrow{\text{polymerization}} [-CH_2-C(Cl)=CH-CH_2-]_n$

(A) Bakelite is a thermosetting polymer prepared by the condensation polymerization of phenol and formaldehyde in the presence of an acid or base catalyst.
Therefore,the correct option is $A$.

(B) Teflon is manufactured by heating tetrafluoroethene with a free radical or persulphate catalyst at high pressures.
The chemical reaction is:
$n CF_2=CF_2 \xrightarrow{\text{Catalyst, High Pressure}} -(CF_2-CF_2)-_n$
Thus,the monomer used to prepare Teflon is tetrafluoroethene $(CF_2=CF_2)$.

(A) $PHBV$ stands for Poly $\beta$-hydroxybutyrate-co-$\beta$-hydroxyvalerate.
It is a copolymer obtained by the polymerization of $3-$hydroxybutanoic acid and $3-$hydroxypentanoic acid.
These monomers undergo condensation polymerization to form the biodegradable polyester $PHBV$.

(C) High density polythene $(HDPE)$ is manufactured by the addition polymerisation of ethene in the presence of a Ziegler-Natta catalyst.
The Ziegler-Natta catalyst consists of a mixture of triethylaluminium $(Al(C_{2}H_{5})_{3})$ and titanium tetrachloride $(TiCl_{4})$.