Biodegradability & disposal of polymers

This question is about polymers.

A section of the polymer PVC is shown.

Name the monomer used to make PVC.

Draw the structure of the monomer used to make PVC.

Structure

State why PVC is not biodegradable.

Diisobutyl phthalate (DIBP) is a plasticiser added to PVC to modify its properties.

State how the properties of PVC are modified by the addition of DIBP.

An incomplete equation for the reaction used to make DIBP is shown.

Complete the equation.

Give the name of the mechanism for this reaction.

Deduce the empirical formula of DIBP.

Empirical formula of DIBP

A different plasticiser, DEHA, is added to PVC used for food packaging.

The structure of DEHA is

Identify the organic compound that would react with hexanedioic acid to form DEHA.

DEHA can be absorbed into food from PVC packaging.

In an investigation, 1 kg samples of three different foods are stored in PVC packaging for 30 days.

Table 1 shows the water content, fat content and mass of DEHA in each type of food after 30 days.

Use your knowledge of intermolecular forces to explain these results.

The polymer nylon 6,6 can be made from hexanedioyl dichloride and hexane-1,6-diamine.

Figure 2 shows an incomplete mechanism for the first steps in this reaction.

Draw the missing intermediate in the box in Figure 2.

Complete Figure 2 by adding the curly arrows and any relevant lone pairs of electrons involved in these steps in the mechanism.

The polymer nylon 6 can be made by heating caprolactam with water.

Figure 3 shows the species involved in the first three steps of the mechanism for this reaction.

Complete Figure 3 by adding the curly arrows and any relevant lone pairs of electrons involved in these steps in the mechanism.

Which statement concerning nylon-6,6 is correct?

Which type of polymer is most difficult to hydrolyse?

Which polymer is not hydrolysed when heated with aqueous alkali?

This question is about ethanedioic acid (HOOCCOOH) and the ethanedioate ion (⁻OOCCOO⁻).

Ethanedioic acid reacts with propane-1,3-diol (HOCH₂CH₂CH₂OH) to form a polyester.

Draw the repeating unit of this polyester.

Explain why polyesters are biodegradable but polyalkenes are not biodegradable.

Sodium ethanedioate is used to find the concentration of solutions of potassium manganate(VII) by titration. The equation for this reaction is

A standard solution is made by dissolving 162 mg of Na₂C₂O₄ (M_r = 134.0) in water and making up to 250 cm³ in a volumetric flask.

25.0 cm³ of this solution and an excess of sulfuric acid are added to a conical flask. The mixture is warmed and titrated with potassium manganate(VII) solution. The titration is repeated until concordant results are obtained.

Calculate the concentration, in mol dm^–3, of the potassium manganate(VII) solution.

Figure 1 shows the 25.0 cm³ pipette used to measure the sodium ethanedioate solution.

On Figure 1, draw the meniscus of the solution when the pipette is ready to transfer 25.0 cm³ of the sodium ethanedioate solution.

Potassium manganate(VII) is oxidising and harmful. Sodium ethanedioate is toxic.

Suggest safety precautions, other than eye protection, that should be taken when:

• filling the burette with potassium manganate(VII) solution

• dissolving the solid sodium ethanedioate in water.

Filling the burette

Dissolving the solid

State the colour change seen at the end point of each titration.

Figure 2 shows the burette containing potassium manganate(VII) solution.

Give two practical steps needed before recording the initial burette reading.

When Na₂C₂O₄(aq) is added to a solution containing [Fe(H₂O)₆]³⁺ ions, a reaction occurs in which all six water ligands are replaced by ethanedioate ions.

Explain why the replacement of the water ligands by ethanedioate ions is favourable. In your answer refer to:

• the enthalpy and entropy changes for the reaction

• how the enthalpy and entropy changes influence the free-energy change for the reaction.

Which type of polymer is not hydrolysed by heating with concentrated aqueous sodium hydroxide?

The outer layers of some golf balls are made from a polymer called polyisoprene. The isoprene monomer is a non-cyclic branched hydrocarbon that contains 88.2 % carbon by mass. The empirical formula of isoprene is the same as its molecular formula.

Deduce the molecular formula of isoprene and suggest a possible structure.

Molecular formula

Structure

The insides of some golf balls are made from a mixture of three other polymers. The repeating unit for one of these polymers is shown.

Draw the skeletal formula of the monomer used to make this polymer.

Give the IUPAC name of the monomer.

Skeletal formula of monomer

A second polymer in the mixture has a repeating unit with the structure shown.

The third polymer in the mixture is a stereoisomer of this polymer.

Draw the structure of the repeating unit of the third polymer.

Give a reason why this type of stereoisomerism arises.

Repeating unit

Golf balls recovered from lakes and ponds can be used again even after being in water for several years.

Explain why these golf balls do not biodegrade.

Give the full IUPAC name of isomer P.

A sample of P was mixed with an excess of oxygen and the mixture ignited. After cooling to the original temperature, the total volume of gas remaining was

When this gas mixture was passed through aqueous sodium hydroxide, the carbon dioxide reacted and the volume of gas decreased to 155 cm³

Both gas volumes were measured at 25 °C and 105 kPa

Write an equation for the combustion of P in an excess of oxygen and calculate the mass, in mg, of P used.

The gas constant R = 8.31 J K⁻¹ mol⁻¹

Mass of P used mg

Isomer Q (C₆H₁₀O₂) is a cyclic compound. The infrared spectrum of Q is shown in Figure 4 and the¹³C NMR spectrum of Q is shown in Figure 5.

Use these spectra and Tables A and C in the Data Booklet to deduce the structure of Q. In your answer, state one piece of evidence you have used from each spectrum.

Structure of Q.

Evidence from Figure 4

Evidence from Figure 5

Isomers R and S are shown.

Although the¹³C spectra of R and S both show the same number of peaks, the spectra can be used to distinguish between the isomers.

Justify this statement using Table C from the Data Booklet.

Give the number of peaks for each isomer.

Justification

Although the¹H spectra of R and S both show the same number of peaks, the spectra can be used to distinguish between the isomers.

Justify this statement using the splitting patterns of the peaks.

Give the number of peaks for each isomer.

Justification

The action of heat on 5-hydroxyhexanoic acid can lead to two different products.

On gentle heating, 5-hydroxyhexanoic acid loses water to form a cyclic

Under different conditions, 5-hydroxyhexanoic acid forms a polyester.

Draw the structure of T.

Draw the repeating unit of the polyester and name the type of polymerisation.

Structure of T

Repeating unit of polyester

Type of polymerisation

Isomer U is shown.

The polymer formed by U and the polymer formed by 5-hydroxyhexanoic acid in Question 10.6 both contain ester groups that can be hydrolysed.

Draw the repeating unit of the polymer formed by U.

Justify the statement that, although both polymer structures contain ester groups, the polymer formed by U is not biodegradable.

Repeating unit of polymer formed by U.

Justification