General methods of preparation and mechanism of polymerisation Questions in English

(B) The polymerization of ethene occurs under high pressure and temperature conditions.
$n(CH_2 = CH_2) \xrightarrow[\text{high pressure}]{400\,^oC} (-CH_2 - CH_2 -)_n$
This process results in the formation of polyethylene.

(C) The synthesis of $PVC$ (polyvinyl chloride) from vinyl chloride $(CH_2=CH-Cl)$ involves the joining of many monomer units to form a long-chain polymer.
This process is known as polymerization.
The reaction is represented as:
$n(CH_2=CH-Cl) \xrightarrow{\text{Polymerization}} (-CH_2-CH(Cl)-)_n$ $(PVC)$

(A) Chloroprene is the common name for the monomer $2-$chloro$-1, 3-$butadiene.
Its chemical structure is $CH_2=C(Cl)-CH=CH_2$.

(B) The $Ziegler-Natta$ catalyst is a mixture of a transition metal compound,typically $TiCl_4$,and an organometallic compound,typically $Al(C_2H_5)_3$ (triethylaluminum).
The polymerization reaction is:
$nCH_3-CH=CH_2 \xrightarrow{TiCl_4 + Al(C_2H_5)_3} [-CH_2-CH(CH_3)-]_n$
Thus,the correct components are $TiCl_4$ and $Al(C_2H_5)_3$.

(B) Ziegler-Natta catalyst,which is a mixture of $TiCl_4$ and $Al(C_2H_5)_3$,is used for the coordination polymerization of alkenes like ethene and propene to produce high-density polymers.

(C) The Ziegler-Natta catalyst is a mixture of triethylaluminium and titanium tetrachloride,represented as $Al(C_2H_5)_3 + TiCl_4$.
It is widely used in the industrial polymerization of alkenes to produce high-density polymers like polyethylene.

(A) The monomer $CH_2 = CHCl$ (Vinyl Chloride) undergoes polymerization to form Polyvinyl Chloride $(PVC)$,which is a widely used plastic.
The reaction is:
$n(CH_2 = CHCl) \xrightarrow{\text{Polymerization}} (-CH_2 - CHCl -)_n$
Therefore,the correct option is $A$.

(B) The reaction sequence is as follows:
$1$. $2CHCl_3 \xrightarrow[SbF_3]{HF} 2CHF_2Cl$
$2$. $2CHF_2Cl \xrightarrow{800^{\circ}C} CF_2=CF_2 + 2HCl$
$3$. $nCF_2=CF_2 \xrightarrow{\text{Polymerisation}} (-CF_2-CF_2-)_n$
The final product is Teflon (Polytetrafluoroethylene).

(A) The reaction between a glycol (a diol) and a dicarboxylic acid is a condensation polymerization reaction.
This reaction involves the elimination of water molecules to form an ester linkage between the monomer units.
The resulting polymer is known as a polyester.
For example,the reaction between ethylene glycol and terephthalic acid produces the polyester known as Terylene or Dacron.

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

(A) Thermosetting plastics are polymers that undergo a chemical change when heated and cannot be reshaped once cured.
Formaldehyde is a key raw material used in the production of thermosetting resins,such as phenol-formaldehyde (Bakelite) and melamine-formaldehyde resins.

(B) Natural rubber is an addition polymer of isoprene ($2$-methyl-$1,3$-butadiene).
The polymerization reaction is as follows:
$nCH_2=C(CH_3)-CH=CH_2 \xrightarrow{\text{Polymerization}} -[CH_2-C(CH_3)=CH-CH_2]_n-$

(C) . Step-growth polymerization involves a condensation reaction between two difunctional monomers to produce a dimer,which in turn produces a tetramer and so on,with the loss of simple molecules like $H_2O, NH_3, HCl$,etc. Nylon is a condensation polymer formed by step-growth polymerization.

(D) Chain growth polymer is also known as addition polymer.
$A$ chain-growth polymer is a polymer that is formed when molecules of the same monomer or different monomers add together on a large scale to form the polymer.
Out of the given polymers,Teflon is a chain-growth polymer as the molecules of tetrafluoroethylene $(CF_2=CF_2)$ simply add together to form the polymer.

(D) Chain-growth polymerization (or addition polymerization) involves the linking together of molecules incorporating double or triple carbon-carbon bonds.
For example,$Polypropylene$ polymerizes by chain-growth polymerization of propylene $(CH_2=CH-CH_3)$.
Nylon-$6$,Dacron,and Glyptal are formed by the step-growth polymerization process.

(B) Nylon$-66$ is a synthetic polymer formed by the condensation polymerization of adipic acid $(HOOC(CH_2)_4COOH)$ and hexamethylenediamine $(H_2N(CH_2)_6NH_2)$.
During this process,water molecules $(H_2O)$ are eliminated as a byproduct,which is characteristic of condensation polymerization.

(C) Natural rubber is a polymer of isoprene ($2$-methyl-$1,3$-butadiene).
In the polymerization process, the isoprene units are linked primarily in a $1,4$-addition manner.
This linkage occurs in a $Head-to-tail$ fashion, where the $Head$ ($CH_2$ group) of one unit joins to the $Tail$ ($CH_2$ group) of the next unit.
This configuration is favored due to steric effects and results in the formation of cis-$1,4$-polyisoprene.

(D) The process of converting monomers into polymers is known as polymerization.
Polymerization can occur through various mechanisms,such as addition polymerization (as shown in the image,which involves the formation of a carbocation intermediate via protonation) or condensation polymerization.
However,the general term for the reaction between monomers to form a polymer is polymerization.
Given the options,none of the specific mechanisms listed (Hydrolysis,Condensation,Protonation) universally describe all polymerization processes.
Since the provided image specifically depicts an addition polymerization mechanism initiated by protonation,and none of the options perfectly describe the general process of polymerization,the most appropriate choice among the given options is $D$.

(A) Polymer formation from monomers starts by condensation reaction between monomers by removal of small molecules like $H_2O$,$HCl$,etc.

(B) The condensation polymerization of hexamethylenediamine and adipic acid at high temperatures $(553 \ K)$ in an inert nitrogen atmosphere results in the formation of a molten (liquid) state of the polymer,which is then extruded to form fibers.
$n \ H_2N-(CH_2)_6-NH_2 + n \ HOOC-(CH_2)_4-COOH$ $\xrightarrow{553 \ K, \ N_2} [-NH-(CH_2)_6-NH-CO-(CH_2)_4-CO-]_n + 2n \ H_2O$
This process yields a liquid polymer of nylon $66$.

(B) $ (b) $ Condensation polymerization because the reaction involves the loss of small molecules like $ H_2O $ or $ CH_3OH $ during the formation of the polymer chain.

(A) In addition polymerization (also known as chain-growth polymerization),monomer units containing double or triple bonds add to the growing polymer chain without the loss of any small molecules.
$PVC$ (Polyvinyl chloride) is formed by the addition polymerization of vinyl chloride $(CH_2=CHCl)$ monomers.
Nylon,Terylene,and Polyamides are typically formed through condensation polymerization,where small molecules like $H_2O$ or $CH_3OH$ are eliminated as by-products during the reaction.

(C) Condensation polymerization involves the elimination of small molecules like $H_2O$ or $NH_3$.
The formation of mesityl oxide from acetone is a condensation reaction where a water molecule is eliminated:
$2 CH_3COCH_3 \rightarrow CH_3C(CH_3)=CHCOCH_3 + H_2O$

(A) The monomer of polythene is ethylene $(CH_2=CH_2)$.
During the process of addition polymerisation,$n$ molecules of ethylene undergo polymerisation to form polythene.
The reaction is as follows:
$n CH_2 = CH_2 \to (-CH_2 - CH_2-)_n$

(C) . The monomer of polypropylene is propene $(CH_3-CH=CH_2)$.
$n CH_3-CH=CH_2 \to -(CH_2-CH(CH_3))_n-$ (Polypropylene).

(C) Lactide can be polymerized to polylactic acid (polylactide),which is a thermoplastic polyester with the backbone formula $(C_3H_4O_2)_n$.
It is formally obtained by the ring-opening polymerization or condensation of lactic acid in the presence of various metal catalysts like $ZnCl_2$.

(B) Phenol-formaldehyde resins are formed by a step-growth polymerization or condensation polymerization reaction.
This reaction is typically acid- or base-catalyzed and involves the elimination of small molecules like water $(H_2O)$.
Since the process involves the reaction of monomers with the loss of small molecules,it is classified as condensation polymerization.

(B) $PVC$ (Polyvinyl chloride) is obtained by the free radical polymerization of vinyl chloride $(CH_2=CH-Cl)$.
The reaction is:
$n(CH_2=CH-Cl) \xrightarrow{\text{polymerization}} -(CH_2-CH(Cl))_n-$

(A) $Nylon-6,6$ is a polyamide formed by the condensation polymerization of $Hexamethylenediamine$ and $Adipic \ acid$.
Thus,$Adipic \ acid$ is a key raw material used in its production.

(C) Nylon is a type of polyamide,which is a condensation polymer.
These polymers are formed by the reaction between a dicarboxylic acid and a diamine.
For example,$Nylon-6,6$ is synthesized by the condensation polymerization of adipic acid $(HOOC-(CH_2)_4-COOH)$ and hexamethylenediamine $(H_2N-(CH_2)_6-NH_2)$.

(A) $PVC$ (Polyvinyl chloride) is prepared by the free radical polymerisation of vinyl chloride monomer.
In this process,organic peroxides such as benzoyl peroxide or other peroxides are used as initiators to generate free radicals,which initiate the polymerisation reaction.

(B) The catalyst used in the manufacture of high-density polyethylene by the $Ziegler-Natta$ method is $TiCl_4$ (titanium tetrachloride) and $(C_2H_5)_3Al$ (triethyl aluminium).

(C) The monomer chloroethene,also known as vinyl chloride $(CH_2=CHCl)$,undergoes addition polymerization to form polyvinyl chloride,commonly known as $PVC$.
The reaction is: $n(CH_2=CHCl) \rightarrow -[CH_2-CHCl]_n- (PVC)$.

(A) The catalyst used for the polymerisation of olefins,such as ethene to form high-density polyethylene,is the Ziegler-Natta catalyst.
It is typically a mixture of triethylaluminium $(Al(C_2H_5)_3)$ and titanium tetrachloride $(TiCl_4)$.

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

(A) Terylene (Dacron) is a polyester fibre which is prepared by the condensation polymerization of ethylene glycol and terephthalic acid with the elimination of water molecules.
The chemical reaction is:
$nHOCH_2CH_2OH + nHOOCC_6H_4COOH \rightarrow [-OCH_2CH_2OCOC_6H_4CO-]_n + 2nH_2O$
This reaction takes place at a temperature of about $425-475 \ K$ in the presence of a zinc acetate-antimony trioxide catalyst.

(D) $PVC$ (Polyvinyl Chloride) is prepared by the addition polymerization of vinyl chloride $(CH_2=CHCl)$.
The $IUPAC$ name of vinyl chloride is $1-chloroethene$.

(C) The combination of triethyl aluminium $(C_2H_5)_3Al$ and titanium tetrachloride $TiCl_4$ is known as the $Ziegler-Natta$ catalyst.
It is widely used in the polymerization of alkenes,such as the production of high-density polyethylene $(HDPE)$.

(C) $Terylene$ (also known as $Dacron$) is a condensation polymer formed by the polymerization of $Ethylene \ glycol$ and $Terephthalic \ acid$.
The reaction is as follows:
$n \ HO-CH_2-CH_2-OH + n \ HOOC-C_6H_4-COOH \rightarrow -[O-CH_2-CH_2-O-CO-C_6H_4-CO]_n- + 2n \ H_2O$
Thus,the correct monomer is $Terephthalic \ acid$.

(D) The monomer $F_2C = CF_2$ is known as tetrafluoroethene.
Polymerization of tetrafluoroethene under high pressure in the presence of a peroxide or persulphate catalyst yields polytetrafluoroethene,commonly known as Teflon.
Therefore,$F_2C = CF_2$ is the monomer of Teflon.

(A) Caprolactam is heated with water at high temperature to undergo ring-opening polymerization to form Nylon-$6$.
Therefore,the correct option is $(A)$.

(C) Neoprene is a synthetic rubber formed by the polymerization of chloroprene ($2$-chloro-$1,3$-butadiene).
The reaction is: $n(CH_2=C(Cl)-CH=CH_2) \to -(CH_2-C(Cl)=CH-CH_2)_n-$ (Neoprene).

(B) Polyvinyl chloride $(PVC)$ is a polymer formed by the addition polymerization of vinyl chloride monomer $(CH_2=CHCl)$.
In addition polymerization,monomer units add together to form a polymer chain without the loss of any small molecules.
Since $PVC$ is formed by the repeated addition of vinyl chloride units,it is classified as an addition polymer of vinyl chloride.
Isomers are compounds with the same molecular formula but different structures,while allotropes are different structural forms of the same element. Neither term applies to the relationship between a monomer and its polymer.

(B) Acrylonitrile $(CH_2=CH-CN)$ undergoes addition polymerization to form polyacrylonitrile,which is commercially known as $Orlon$ or $Acrilan$.

(B) Polyvinyl chloride $(PVC)$ is a synthetic polymer formed by the addition polymerization of vinyl chloride monomers.
The monomer unit of $PVC$ is vinyl chloride,which has the chemical formula $CH_2 = CH - Cl$.
During polymerization,the double bond breaks,allowing the monomers to link together to form the long chain polymer structure.

(A) Teflon is a polymer of tetrafluoroethene. The polymerization reaction is as follows:
$nCF_2 = CF_2 \xrightarrow{\text{catalyst, high pressure}} [CF_2 - CF_2]_n$
Thus,the correct option is $(A)$.

(B) Polythene (or polyethylene) is a polymer formed by the addition polymerization of ethylene $(CH_2=CH_2)$ monomers.
The reaction can be represented as:
$n(CH_2=CH_2) \rightarrow -[CH_2-CH_2]_n-$

(A) The monomer used in the preparation of Nylon-$6$ is caprolactam.
Caprolactam undergoes ring-opening polymerization in the presence of water at high temperatures to form Nylon-$6$.
$\text{Caprolactam} + H_2O \xrightarrow{\Delta} [NH-(CH_2)_5-CO]_n$ (Nylon-$6$)

(C) The Ziegler-Natta process involves the polymerization of ethylene using a catalyst (typically $TiCl_4$ and $(C_2H_5)_3Al$).
This reaction is carried out at a temperature range of $50\,^oC$ to $80\,^oC$ and under low pressure.
Therefore,the correct option is $(C)$.

(A) $HDPE$ is prepared by coordination polymerization using the Ziegler-Natta catalyst (a mixture of triethylaluminium and titanium tetrachloride).
This process occurs through the formation of coordination complexes.
Ethylene molecules coordinate with the transition metal catalyst,leading to linear chain growth.
The resulting polymer has a high density $(0.97 \ g/cm^3)$ and a higher melting point $(403 \ K)$ compared to $LDPE$ (density $0.92 \ g/cm^3$ and melting point $384 \ K$).