Polymerisation: Chemistry 9701 (Cambridge International AS & A Level)

A section of an addition polymer chain is represented by the repeat unit

$\left(-\text{CH}_2-\text{CH}(\text{CH}(\text{CH}_3)_2)-\right)_n$

Which alkene was used as the monomer to form this polymer?

Methyl 2-methylpropenoate, $\text{CH}_2=\text{C}(\text{CH}_3)\text{COOCH}_3$, is the monomer used to manufacture a transparent addition polymer marketed as acrylic sheeting, widely used for aquarium windows and aircraft canopies.

(a) State the type of polymerisation involved, and identify the structural feature of the monomer that makes this type of polymerisation possible. [2]

(b) Deduce the repeat unit of this addition polymer, showing all atoms and bonds clearly. [2]

(c) A section of a different addition polymer chain is represented by the repeat unit $-\text{CH}_2-\text{CHCl}-$. Name the monomer used to form this polymer, and give its structural formula. [2]

(d) Both of these poly(alkene)s resist natural degradation. Explain why they are non-biodegradable, and state one additional hazard associated with disposing of the polymer in (c) by incineration, that does not apply to the polymer in (b). [2]

Propane-1,3-diol, $\text{HOCH}_2\text{CH}_2\text{CH}_2\text{OH}$, and pentanedioic acid, $\text{HOOC}(\text{CH}_2)_3\text{COOH}$, react together by condensation polymerisation to form a polyester.

(a) Deduce the repeat unit of this polyester, and state the number of water molecules released per repeat unit. [3]

(b) A different polyester has the repeat unit $-\text{O}(\text{CH}_2)_4\text{OCO}(\text{CH}_2)_4\text{CO}-$. Identify, by name and structural formula, the two monomers used to form this polyester. [2]

(c) 6-Hydroxyhexanoic acid, $\text{HO}(\text{CH}_2)_5\text{COOH}$, can also undergo condensation polymerisation on its own to form a polyester. Deduce the repeat unit formed, and state the number of water molecules eliminated per repeat unit. [2]

4-Aminobutanoic acid, $\text{H}_2\text{N}(\text{CH}_2)_3\text{COOH}$, can undergo condensation polymerisation on its own to form a polyamide.

(a) Deduce the repeat unit of this polyamide, showing the amide link clearly, and state the number of water molecules eliminated per repeat unit. [3]

(b) This polyamide is hydrolysed by heating under reflux with an excess of dilute hydrochloric acid. Name the type of bond broken in the polymer backbone, and give the structural formula of the organic product formed per repeat unit under these acidic conditions. [3]

(c) Poly(alkenes) such as poly(ethene) are not biodegradable, whereas this polyamide can be broken down by hydrolysis in the environment. Explain, in terms of the polarity of the bonds involved, why the poly(alkene) backbone resists this kind of attack but the amide linkages in the polyamide do not. [2]

Pentanedioyl dichloride, $\text{ClOC}(\text{CH}_2)_3\text{COCl}$, is reacted with butane-1,4-diamine, $\text{H}_2\text{N}(\text{CH}_2)_4\text{NH}_2$, to form a polyamide.

Per repeat unit of the polymer formed, how many molecules of hydrogen chloride are eliminated, and how many amide bonds are formed?

But-2-ene, $\text{CH}_3\text{CH}=\text{CHCH}_3$, undergoes addition polymerisation.

Which of the following is the correct repeat unit of the polymer formed?

(a) Propene, $\text{CH}_2=\text{CHCH}_3$, is polymerised by addition polymerisation to form poly(propene). Deduce the repeat unit of poly(propene). [2]

(b) A section of a different addition polymer chain is represented by the repeat unit $-\text{CF}_2-\text{CF}_2-$. Identify, by name and structural formula, the monomer used to form this polymer. [2]

(c) For each of the following, state whether it describes a monomer, or pair of monomers, suited to addition polymerisation or to condensation polymerisation, giving a reason based on the functional group(s) present:

(i) but-1-ene, $\text{CH}_2=\text{CHCH}_2\text{CH}_3$, on its own. [1]

(ii) hexanedioic acid, $\text{HOOC}(\text{CH}_2)_4\text{COOH}$, together with hexane-1,6-diamine, $\text{H}_2\text{N}(\text{CH}_2)_6\text{NH}_2$. [2]

(a) Hexane-1,6-diol, $\text{HO}(\text{CH}_2)_6\text{OH}$, is reacted with propanedioyl dichloride, $\text{ClOCCH}_2\text{COCl}$, to form a polyester. Deduce the repeat unit formed, and state the number and identity of the small molecules eliminated per repeat unit. [3]

(b) A different polyamide has the repeat unit $-\text{NH}(\text{CH}_2)_6\text{NHCO}(\text{CH}_2)_2\text{CO}-$. Identify, by name and structural formula, the two monomers used to form this polyamide. [2]

(c) The polyester formed in (a) is hydrolysed by heating under reflux with an excess of dilute hydrochloric acid. Give the structural formulae of the two organic products formed per repeat unit under these conditions. [2]

A polyester used in biodegradable packaging film is formed from propane-1,3-diol, $\text{HOCH}_2\text{CH}_2\text{CH}_2\text{OH}$, and butanedioic acid, $\text{HOOC}(\text{CH}_2)_2\text{COOH}$, and has the repeat unit $-\text{O}(\text{CH}_2)_3\text{OCO}(\text{CH}_2)_2\text{CO}-$.

(a) The polyester is hydrolysed by heating under reflux with an excess of aqueous sodium hydroxide. Name the type of bond broken, and give the formula(e) of the organic product(s) formed per repeat unit under these alkaline conditions. [3]

(b) The same polyester is instead hydrolysed by heating under reflux with an excess of dilute hydrochloric acid. Give the formula(e) of the organic product(s) formed per repeat unit under these acidic conditions, and explain why one of the products differs in form from the corresponding product in (a). [3]

(c) A sample of poly(ethene) is also treated under the same alkaline reflux conditions as in (a). State, with a reason, whether the poly(ethene) is hydrolysed under these conditions. [2]

Hexane-1,6-diamine, $\text{H}_2\text{N}(\text{CH}_2)_6\text{NH}_2$, and heptanedioic acid, $\text{HOOC}(\text{CH}_2)_5\text{COOH}$, react together by condensation polymerisation to form a polyamide used in synthetic fibres.

(a) Deduce the repeat unit of this polyamide, showing the amide link clearly, and state the number of water molecules eliminated per repeat unit. [3]

(b) The polyamide is hydrolysed by heating under reflux with an excess of aqueous sodium hydroxide. Name the type of bond broken in the polymer backbone, and give the structural formula(e) of the organic product(s) formed per repeat unit under these alkaline conditions. [3]

(c) State and explain how the form of the amine-containing product in (b) would differ if the same polyamide were instead hydrolysed by heating under reflux with an excess of dilute hydrochloric acid. [2]