NT Exampro 1

1. Substitution reactions of halogenoalkanes can proceed via an SN1 or SN2 mechanism. In the case of SN1, a chiral halogenoalkane does not give a chiral product.

(i) Give the equation for the reaction between 2–bromobutane and aqueous hydroxide ions, using structural formulae.

(ii) Give the mechanism for this SN1 reaction.

(iii) Explain why the product is not chiral.

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2. How does the rate of nucleophilic substitution of halogenoalkanes, RX, change with the halogen in the compound? Give reasons for your answer.

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3. (a) (i) Explain the term homologous series.

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(ii) To which homologous series does ethene, C2H4, belong?

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NT Exampro 2

(b) Draw the full structural formulae, showing all the bonds, for each of the following:

(i) The organic product of the reaction of ethene, C2H4, with aqueous potassium manganate(VII) and sulphuric acid.

(2)

(ii) 3,4-dimethy1hex-2-ene.

(2)

(iii) A repeating unit of poly(propene).

(2)

(c) Ethene reacts with hydrogen chloride gas to form C2H5Cl.

(i) What type of reaction is this?

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(ii) Give the systematic name for C2H5C1.

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(Total 12 marks)

4. (a) Predict the structural formula of the organic product from the reaction of 1-bromopropane, CH3CH2CH2Br, with;

(i) aqueous potassium cyanide solution.

(1)

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NT Exampro 3

(ii) ammonia gas.

(1)

(b) Give details of a chemical test you could do to distinguish between 2-chiorobutane and butan-2-ol, including the expected observations with each compound.

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(c) (i) Draw the full structural formula showing all the bonds for the isomer of butan-2-ol that is a tertiary alcohol.

(1)

(ii) Give details of a chemical test you could do to distinguish between butan-2-ol and its isomer drawn in (i) and the observations you would expect to make.

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NT Exampro 4

(iii) Explain the chemistry involved in the test you described in part (ii).

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(Total 11 marks)

5. 2-bromobutane was heated with excess aqueous potassium hydroxide until hydrolysis was complete. The resulting mixture was divided into two portions.

(a) When aqueous nitric acid followed by aqueous silver nitrate was added to one portion a precipitate was formed.

(i) Explain why aqueous nitric acid was added to the reaction mixture before aqueous silver nitrate.

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(ii) Give the colour and formula of the precipitate formed.

Colour................................ .Formula.......................................................... (2)

(iii) Suggest the effect of adding concentrated aqueous ammonia to the precipitate.

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NT Exampro 5

(b) The alcohol produced by the hydrolysis was separated from the second portion of the

reaction mixture. Give the formula of a reagent which could be used to test for the presence of the -OH group in the alcohol. Describe the observation you would expect to make and give the formula of any one of the products of the test.

Formula of reagent ...............................................

Observation ............................................................................................................

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Formula of product .............................................. (3)

(Total 8 marks)

6. In an experiment to prepare cyclohexene, C6H10, concentrated sulphuric acid was added drop by drop to 6.00 g of cyclohexanol, C6H11OH, in the apparatus shown in the diagram below.

Sulphuric acid

Cyclohexanol

HeatCyclohexene

As the reaction took place cyclohexene distilled over into the collection flask and a black deposit of carbon formed in the reaction flask.

The equation for the main reaction is

C6H11OH(l) → C6H10(l) + H2O(l)

After purification 1.80 g of cyclohexene was collected.

(a) (i) Calculate the amount (number of moles) of cyclohexanol used in the experiment.

(2)

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NT Exampro 6

(ii) Calculate the mass of cyclohexene that would be formed if all of the cyclobexanol

was converted into cyclohexene.

(2)

(iii) Calculate the percentage yield of cyclohexene.

(1)

(b) Explain the relevance of the boiling points of cyclohexanol (161°C) and cyclohexene (83.3°C) to the success of the preparation.

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(c) Explain why the formation of carbon reduces the yield of cyclohexene.

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(d) Using the information below, suggest what precautions should be taken when clearing up the apparatus after the preparation.

Sulphuric Acid H2SO4 (Concentrated)

Very corrosive, causes severe burns. With water, heat is evolved.

(2)

(e) Suggest a reagent which could be used to test for the presence of the alkene double bond in cyclohexene. Give the expected result of the test.

Reagent...................................................................................................................

Result...................................................................................................................... (2)

(Total 12 marks)

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NT Exampro 7

7. Alkanes are often used as fuels in a variety of situations. Methane, CH4 is used as a gas to heat

houses and offices whereas octane, C8H18 is used in petrol.

Methane burns to form carbon dioxide and water as follows:

CH4 + 2O2 → CO2 + 2H2O

The enthalpy of combustion of methane is –890 kJ mol–1. The enthalpy of combustion of octane is –5512 kJ mol–1. Octane might seem a much better fuel than methane in all circumstances but this is not necessarily so.

(a) (i) Define the term standard enthalpy of combustion.

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(ii) Why does methane not react with air unless a flame or spark is applied to the mixture?

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….……………………………………………………………………………. (2)

(ii) Draw a reaction profile diagram for the combustion of methane.

(3)

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NT Exampro 8

(b) (i) Write a balanced equation for the complete combustion of octane in oxygen.

….……………………………………………………………………………. (2)

(ii) What volume of air, which contains 20% oxygen, would be needed to burn one mole of octane? (Under the conditions of the experiment, 1 mole of gas occupies 24 dm³).

(2)

(iii) Burning 1.00 g of octane produces 48.4 kJ of energy. Calculate the heat energy produced by burning 1.00 g of methane.

(2)

(iv) Burning 1.00 dm³ of liquid octane releases 33800 kJ of energy. Calculate the heat energy released on burning 1.00 dm³ of gaseous methane. (Under the conditions of the experiment, 1 mole of gas occupies 24 dm³).

(2)

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NT Exampro 9

(v) Suggest why octane is preferred to methane as a fuel for motor cars.

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(c) What role does methane play in the industrial production of ammonia?

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…...…………………………………………………………………………………. (2)

(Total 21 marks)

8. Consider the following reaction scheme, involving compounds A to E.

C H O C H O A B

K Cr O indilute sulphuricacid

C D

3

2 2 7

38 6

conc sulphuric acid

HBr

• None of the compounds in the scheme shows cis-trans isomerism.

• D reacts with potassium cyanide to form 2-methylpropanonitrile.

• An isomer of A will form C by the same route but will not produce B by reaction with potassium dichromate(VI) acidified with dilute sulphuric acid. Instead it makes E, C3H6O2

Identify using a name or structural formulae:

A

B

C

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NT Exampro 10

D

E

(Total 10 marks)

9. Four of the structural isomers of C4H10O are alcohols. One of these isomers is butan-2-ol.

(a) Draw the structural formulaE of two other alcohols with molecular formula C4 H10 O and name each of these isomers.

Diagrams

Isomer 1 Isomer 2

Name of isomer 1 Name of isomer 2

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(b) A sample of butan-2-ol, C4H9OH, was heated with a mixture of sulphuric acid and potassium dichromate (VI).

(i) State the colour change that would be observed during the reaction.

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NT Exampro 11

(ii) Give the name of the organic product formed, and name the type of reaction

occurring.

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(Total 7 marks)

10. (a) A sample of 2-bromobutane was heated with potassium hydroxide in ethanolic solution. A reaction occurred producing a mixture of but-1-ene and but-2-ene.

(i) Write an equation for the above reaction to show the production of either but-1-ene or but-2-ene.

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(ii) State the type of reaction taking place.

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(b) Some bromine solution was shaken with a sample of but-2-ene, and a reaction occurred.

(i) State what would be seen during this reaction.

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(ii) Draw the structural formula of the product of this reaction, and name this product.

Diagram:

Name ............................................................................................................... (2)

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NT Exampro 12

(c) But-2-ene can exist as two stereoisomers.

(i) Draw the structural formula of the two stereoisomers of but-2-ene.

(2)

(ii) Explain why but-2-ene exists as two stereoisomers, and name this type of isomerism.

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(Total 9 marks)

11. Consider the following reaction scheme:

C H C H Br (major product)Propene

step 2

step 1

aqueous NaOH

C H O

CH COCH

33

4

3

3 3

76

8

S

PQ

KMnO inalkali

step 3oxidation

(a) (i) Give the reagent and the conditions needed for step 1.

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NT Exampro 13

(ii) Give the structural formula of S.

(1)

(b) (i) Give the structural formula of P.

(1)

(ii) State the type of reaction in:

step 1 ................................................................................................................ (2)

the conversion of S to P .................................................................................. (2)

(c) (i) Give the reagent and the conditions needed for step 2.

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(ii) Give the reagents and the conditions needed for step 3.

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(d) Give the structural formula for compound Q.

(1)

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NT Exampro 14

(e) If S is reacted with a solution of hydroxide ions in ethanol P is not the product.

Draw the structure of the compound that is produced in this reaction.

(1)

(Total 15 marks)

12. (a) Ethene and propene are in the same homologous series. Explain the term homologous series.

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(b) (i) Draw a representative length of the polymer chain of poly(propene).

(2)

(ii) State, with a reason, the empirical formula of poly(propene).

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NT Exampro 15

(c) Poly(propene) does not have a sharp melting temperature, but softens over a range of

temperature. Suggest why this is so.

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(d) (i) Tetrafluoroethene, C2F4, also forms a polymer. Suggest why this polymer is very inert.

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(ii) Give one use for poly(tetrafluoroethene).

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(e) Ethane and ethene both react with bromine. Ethane does not react at room temperature in the dark, whereas ethene does so extremely quickly. Explain in terms of the bonding in each molecule why this is so.

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(Total 14 marks)

13. (a) A compound Z has the composition (by mass) of 68.2% C, 13.6% H and 18.2% O. It has a relative molecular mass of 88.

(i) Find the empirical formula of Z.

(3)

(ii) Deduce the molecular formula of Z.

(2)

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NT Exampro 16

(b) Compound Z is an alcohol, which can be tested for with phosphorus pentachloride,PCl5.

(i) Using the symbol ROH to represent compound Z, write an equation to show how it reacts with PCl5.

………….……………….…………………………………………………….. (2)

(ii) What would you see as the test is performed?

………….……………….…………………………………………………….. (1)

(c) (i) Draw a full structural formula for Z that is a branched-chain primary alcohol.

(2)

(ii) Draw the full structural formula of the compound that would be obtained if the primary alcohol in (c) (i) were to be oxidised so that the product distils over as it is formed.

(1)

(iii) Suggest a suitable oxidising mixture for the reaction in (c) (ii).

………….……………….…………………………………………………….. (2)

(iv) State what type of organic compound would be formed if the reaction in (c) (ii) were heated under reflux.

………….……………….…………………………………………………….. (1)

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NT Exampro 17

(d) If the alcohol Z is heated with concentrated sulphuric acid, a gas Y is produced.

Gas Y reacts with bromine solution decolourising it.

(i) Draw the functional group present in Y.

(1)

(ii) Suggest a structure for a compound that could be produced from the reaction of bromine with Y.

(2)

(Total 17 marks)

14. (a) The reactivity of organic compounds is related to their bonding. Ethane reacts very slowly with bromine in the dark but rapidly in ultraviolet light; ethene reacts rapidly with bromine even in the dark.

(i) What type of reaction is the reaction of bromine with ethane?

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(ii) Explain the difference in the reactivity of ethane and ethene with bromine in terms of the types of covalent bonding found in these two compounds.

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NT Exampro 18

(b) Halogenoalkanes such as CH3CH2CH2Br react with potassium hydroxide solution in

several ways depending on the conditions.

(i) Name the compound CH3CH2CH2Br.

………….……………….…………………………………………………….. (1)

(ii) Draw the structure of the compound obtained if CH3CH2CH2Br is reacted with KOH in ethanolic solution.

(1)

(iii) Draw the structure of the substance obtained if CH3CH2CH2Br is reacted with KOH in aqueous solution.

(1)

(iv) What is the role of the hydroxide ion in the reaction in (iii)?

………….……………….…………………………………………………….. (1)

(v) CH3CH2CH2Cl reacts much more slowly with aqueous KOH than CH3CH2CH2Br does. Why is this?

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(Total 11 marks)

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NT Exampro 19

15. (a) Bromine reacts with both ethane and ethene.

(i) Write the equations for the reactions below.

Ethane + bromine

...................................................................................................................... (1)

Ethene + bromine

...................................................................................................................... (1)

(ii) Classify the two reactions in terms of the type of reaction occurring.

Ethane + bromine

...................................................................................................................... (2)

Ethene + bromine

...................................................................................................................... (2)

(b) Chloroethene (vinyl chloride), H2C==CHCl, can be polymerised in a similar type of reaction to the polymerisation of ethene.

(i) Draw the full structural formula of the polymer poly(chloroethene), sufficient to make the structure of the polymer clear.

(1)

(ii) State one use of poly(chloroethene).

...................................................................................................................... (1)

(iii) State and explain one environmental problem arising from the disposal of poly(chloroethene).

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(Total 10 marks)

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NT Exampro 20

16. (a) Halogenoalkanes react with many nucleophiles.

Define the term nucleophile.

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............................................................................................................................... (2)

(b) (i) Identify the reagent and conditions necessary for the conversion of iodoethane to ethylamine, C2H5NH2.

Reagent:.........................................................................................................

Conditions:.....................................................................................................

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(ii) State why the rate of reaction would be slower if bromobutane were used in place of iodoethane, with all other conditions remaining the same.

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...................................................................................................................... (1)

(c) Iodoethane reacts with water to form ethanol and hydrogen iodide.

C2H5I + H2O → C2H5OH + HI ∆Hf = +36 kJ mol–1

Use some or all of the data below to calculate the CI bond enthalpy.

Bond Bond enthalpy / kJ mol–1

Bond Bond enthalpy / kJ mol–1

CH 413 HI 298

CC 347 CO 358

HO 464

(3)

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NT Exampro 21

(d) Ethanol was heated under reflux with an excess of a mixture of potassium dichromate(VI)

and dilute sulphuric acid. Draw the full structural formnula of the organic product.

(1)

(Total 10 marks)

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