OCR A Level Chemistry A Synthesis and analytical techniques June 2024 question paper H432/02

All organic compounds have covalent bonds.

What is the electrostatic attraction in a covalent bond between?

A A shared pair of electrons and the nuclei of the bonded atoms

B Cations and delocalised electrons

C Oppositely charged ions

D Two molecules

Hydrogen reacts much more readily with alkenes than with alkanes.

Why is this?

A Alkenes are polar molecules whereas alkanes are not.

B All atoms in an alkane have a full outer shell of electrons.

C The bond enthalpy of C–C bonds is higher than that of bonds.

D The bond enthalpy of C–C bonds is lower than that of bonds.

A student investigates the rate of hydrolysis of different iodoalkanes using aqueous silver nitrate in ethanol.

What colour of precipitate is seen?

A Brown

B Cream

C White

D Yellow

The structure of but-1-ene is shown below.

Which row has the correct shape around carbon atoms labelled x and y ?

Geraniol, shown below, is a component in many natural oils.

Which pair of reagents identifies both functional groups in geraniol?

A Acidified dichromate(VI) and 2,4-dinitrophenylhydrazine.

B Bromine water and 2,4-dinitrophenylhydrazine.

C Bromine water and acidified dichromate(VI).

D Tollens’ reagent and aqueous silver nitrate in ethanol.

4.30 g of the alcohol C₅H₉OH, (M_r = 86.0), is burned in oxygen.

Which volume of oxygen gas is needed, in dm³, for this complete combustion of C₅H₉OH, at RTP?

A 1.2

B 2.4

C 5.8

D 8.4

Which statement gives a valid scientific reason for global warming?

A Infrared radiation causes bonds in CH₄ molecules to vibrate more.

B Infrared radiation causes O₂ molecules to vibrate more.

C Ultraviolet radiation causes bonds in CO₂ to vibrate more.

D Ultraviolet radiation causes bonds in CFC molecules to break.

The CFC CCl₂F₂ can cause the breakdown of ozone in the upper atmosphere.

Which initiation step could occur with ultraviolet radiation to catalyse this breakdown?

Which compound is a secondary amide?

1.35 g of ethylamine gas, CH₃CH₂NH₂ (M_r = 45.0), is reacted with 20 cm³ of 2.0 mol dm^–3 hydrochloric acid forming a solution of ethylammonium chloride.

What is the concentration of ethylammonium chloride in mol dm^–3?

A 0.03

B 0.67

C 1.50

D 2.00

Which compound could have produced the IR spectrum shown below?

A HOCH₂CHO

B CH₃CH₂COOH

C CH₃CH₂COOCH₃

D (CH₃)₂C(OH)COOH

1,6-Diaminohexane, H₂N(CH₂)₆NH₂, reacts with hexanedioyl dichloride, Cl OC(CH₂)₄COCl to form a polyamide and one other product.

What is the other product formed in this reaction?

A HC l

B H₂O

C CO

D NH₃

A sample containing a mixture of 3 components, X, Y and Z, is analysed using gas chromatography.

The gas chromatogram below is obtained. The relative peak areas of X, Y and Z are included.

Which statement(s) is/are true?

1 The peak for component X shows the mass of one mole.

2 Component Y stays in the column for longer than component X.

3 Component Z consists of more than half of the sample.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Polymers, such as poly(chloroethene), shown below, are difficult to dispose of.

Poly(chloroethene)

Which statement(s) is/are true about poly(chloroethene)?

1 It is a photodegradable or biodegradable polymer.

2 When incinerated, it produces toxic waste products which need to be removed.

3 It can be recycled and processed for use as an organic feedstock.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Which hydrocarbons are unsaturated?

Which hydrocarbons are alicyclic?

Which hydrocarbons have the general formula C_nH_2n?

What is the systematic name of hydrocarbon C ?

Explain why hydrocarbon D is a Z-stereoisomer.

This question is about reactions of alcohols.

There are 4 structural isomers of C₄H₁₀O that are alcohols: CH₃CH₂CH₂CH₂OH CH₃CH₂CHOHCH₃ (CH₃)₂CHCH₂OH (CH₃)₃COH

Alcohols take part in many different types of reaction, including

• elimination

• oxidation

• substitution

• esterification.

For each type of reaction, choose appropriate reagent(s) and/or catalyst, and show the organic product formed.

Elimination reaction of CH₃CH₂CH₂CH₂OH

Reagent(s) and/or catalyst

organic product

Oxidation reaction of CH₃CH₂CHOHCH₃

Reagent(s) and/or catalyst

organic product

Substitution reaction of (CH₃)₂CHCH₂OH

Reagent(s) and/or catalyst

organic product

Esterification reaction of (CH₃)₃COH

Reagent(s) and/or catalyst

organic product

This question is about haloalkanes.

Haloalkanes can be synthesised by reacting alkanes with halogens in the presence of ultraviolet radiation.

An alkane reacts with bromine to form 2-bromo-2-methylpropane.

Write the equation for this reaction, showing the structures of the organic compounds.

Name the reaction mechanism and the type of bond fission that occurs.

Equation

Name of reaction mechanism........

Type of bond fission........

Describe two limitations of the synthesis of 2-bromo-2-methylpropane from an alkane and bromine.

19* Alkenes and carbonyl compounds take part in addition reactions.

Describe one addition reaction of an alkene and one addition reaction of a carbonyl compound.

Include reagents and reaction mechanisms.

This question is about carboxylic acids and esters.

Short-chain carboxylic acids, such as methanoic acid, HCOOH, are soluble in water.

Explain, with a labelled diagram, how HCOOH interacts with water when it dissolves.

Ester F has the structure shown below.

What is the systematic name for this ester?

Ester F can be prepared from a carboxylic acid in two steps.

Step 1 The carboxylic acid is converted into an acyl chloride.

Step 2 The acyl chloride is converted into ester F.

Write equations for Step 1 and Step 2.

Show organic compounds as structures.

Step 1

Step 2

The repeat unit of a polyester is shown below.

Draw the structures of monomers required to form this polyester.

The compound below contains an ester and an amide group.

Draw the structures of the organic products formed by the complete alkaline hydrolysis of this compound using NaOH(aq).

This question is about aromatic compounds.

Ethylbenzene, C₆H₅CH₂CH₃, can be prepared by reacting benzene with chloroethane, CH₃CH₂Cl, in the presence of Al Cl₃. The Al Cl₃ acts as a halogen carrier.

Ethylbenzene

In the mechanism, chloroethane reacts with the halogen carrier to form a carbocation, which acts as the electrophile.

What is meant by the term electrophile ?

Outline the mechanism for this reaction, including the role of Al Cl₃ as a halogen carrier.

The table shows directing effects for different groups in the electrophilic substitution of aromatic compounds.

The reactions of C₆H₅NH₂ are similar to the reactions of phenol.

Write an equation for the tri-substitution of C₆H₅NH₂ with chlorine.

Explain why chlorine reacts much more readily with C₆H₅NH₂ than with benzene.

-Amino acids have the general formula RCH(NH₂)COOH.

The R group in an -amino acid contains C and H only.

This R group has a molar mass of 91 g mol^–1.

A polymer is formed from 500 molecules of this -amino acid.

Determine the molar mass of this polymer.

Give your answer to the nearest whole number.

molar mass of polymer =........ g mol^–1

Oil of wintergreen is a liquid used in medicine to relieve muscle pain.

Compound H is a component in oil of wintergreen and can be synthesised from compound G, as shown below. The boiling point and density of compound H are stated.

Compound G
Compound H boiling point = 222 °C density = 1.174 g cm⁻³

A student prepares a sample of compound H by the method below.

Step 1 Reflux 8.97 g of compound G for 30 minutes with an excess of methanol in the presence of a small amount of sulfuric acid as a catalyst.

Step 2 Add an excess of aqueous sodium carbonate, Na₂CO₃(aq). Two layers are obtained.

Step 3 Purify the impure compound H that forms from the resulting mixture.

The student follows this method and obtains 5.32 g of pure compound H.

Why does the student use reflux in Step 1 ?

In Step 2, Na₂CO₃(aq) removes the sulfuric acid catalyst and any unreacted compound G from the mixture.

Write equations for this removal.

Removal of sulfuric acid

Removal of unreacted compound G

Compound G

Another student suggests that adding aqueous sodium hydroxide would be more effective in removing the sulfuric acid catalyst than Na₂CO₃(aq).

Comment on whether the student’s suggestion is an improvement for the preparation of compound H.

Calculate the percentage yield of compound H.

Give your answer to three significant figures.

Describe how to purify the impure compound H from the two layers in Step 2.