REACTIONS OF ORGANIC COMPOUNDS IAS TOPIC 13

ALKANES

ALKENES

SUBSTITUTION REACTIONS OF HALOALKANES

HALOALKANES: SUBSTITUTION VERSUS ELIMINATION

OXIDATION OF ALCOHOLS

OTHER REACTIONS OF ALCOHOLS

TEST QUESTION I

TEST QUESTION II

TEST QUESTION III

TEST QUESTION IV

TEST QUESTION V

Questionsheet 1

Questionsheet 2

Questionsheet 3

Questionsheet 4

Questionsheet 5

Questionsheet 6

Questionsheet 7

Questionsheet 8

Questionsheet 9

Questionsheet 10

Questionsheet 11

QUESTIONSHEETS AS LevelCHEMISTRY

18 marks

8 marks

20 marks

15 marks

16 marks

20 marks

18 marks

17 marks

19 marks

18 marks

12 marks

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AuthorsTrevor Birt John BrockingtonDonald E Caddy Kevin FrobisherAndrew Jones Andy ShepherdAdrian Bond Stuart Barker

EditorsJohn BrockingtonStuart Barker

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ALKANES

a) Methane can be chlorinated to give a mixture of four chloromethanes.(i) State the necessary reaction conditions.

....................................................................................................................................................................... [1]

(ii) Write balanced chemical equations for the reactions.

...........................................................................................................................................................................

...........................................................................................................................................................................

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [4]

(iii) Explain, in non-mechanistic terms, why a mixture of chloromethanes is always obtained.

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [2]

(iv) By what technique could the chloromethanes be separated from one another?

....................................................................................................................................................................... [1]

(v) How could the chlorination of methane be carried out so as to favour the formation of chloromethanerather than other organic products?

....................................................................................................................................................................... [1]

(vi) How could the chlorination of methane be carried out so as to favour the formation of chloromethanerather than other organic products?

....................................................................................................................................................................... [1]

TOPIC 13 Questionsheet 1

(Continued...)

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ALKANESTOPIC 13 Questionsheet 1 Continued

18

b) In the chlorination of ethane, the product is a mixture of nine chloroethanes; not six, as might be expected.State the reason for this, and illustrate your answer by writing the structural formulae and IUPAC names of(i) the dichlorides, (ii) the trichlorides, and (iii) the tetrachlorides.

Reason ..............................................................................................................................................................

....................................................................................................................................................................... [1]

(i)

(ii)

(iii)

Tre

trac

hlor

ides

StructrualFormulae

Name

Name

Name

StructrualFormulae

StructrualFormulae

Quality of language [1]

[2]

[2]

[2]

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ALKENES

8

TOPIC 13 Questionsheet 2

a) Write a balanced equation for the complete combustion of propene

....................................................................................................................................................................... [1]

b) Draw the structural formulae of the products of reacting this alkene with the substances in the table below:

(i) Hydrogen and a nickel catalyst at 150ºC (ii) Bromine

[1] [1]

(iii) Hydrogen bromide (show both isomers produced)

[2]

c) C2H

4 is converted by steam and phosphoric acid to C

2H

5OH.

(i) Write down the balanced equation for this reaction.

....................................................................................................................................................................... [1](ii) Draw the structural formulae of both isomers that could be formed from the reaction of the following

alkene with steam and phosphoric acid.

[2]

CH3

CH C CH2

CH3

CH3

CH2

CH CH CH2

CH3

CH3

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20

SUBSITUTION REACTIONS OF HALOALKANES

a) Give the names and structural formulae of:

(i) a primary haloalkane containing three carbon atoms.

....................................................................................................................................................................... [2]

(ii) a secondary haloalkane containing four carbon atoms.

....................................................................................................................................................................... [2]

(iii) a tertiary haloalkane containing four carbon atoms.

....................................................................................................................................................................... [2]

b) (i) Give the reagent and reaction conditions you would use to convert 1-bromopropane into propan-1-ol.

...........................................................................................................................................................................

....................................................................................................................................................................... [2]

(ii) Under what conditions does 1-bromopropane react with the following reagents? Write the equation andname the organic product in each case.

Potassium cyanide

Conditions ............................................................................................................................................. [2]

Equation ................................................................................................................................................ [1]

Name of product .................................................................................................................................... [1]

Ammonia

Conditions ............................................................................................................................................. [2]

Equation ............................................................................................................................................... [1]

Name of product .................................................................................................................................... [1]

(iii) State the type of reaction occurring in both b)(i) and b (ii).

....................................................................................................................................................................... [2]

c) (i) Arrange the following compounds in increasing order of their reactivity towards NaOH(aq):C

2H

5Br , C

2H

5Cl, C

2H

5I.

....................................................................................................................................................................... [1]

(ii) How can this reactivity trend be explained ?

....................................................................................................................................................................... [1]

TOPIC 13 Questionsheet 3

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HALOALKANES: SUBSTITUTION VERSUS ELIMINATION

When 2-bromobutane is warmed with potassium hydroxide in aqueous solution, the main product is accompaniedby two by-products.

a) Give the name of the main product. State the type of reaction taking place and write an equation for it.

Name of main product ................................................................................................................................... [1]

Type of reaction ............................................................................................................................................. [1]

Equation ........................................................................................................................................................ [1]

b) Give the names and structural formulae of the two by-products. State the type of reaction which leads to theirformation and write the equation for the formation of one of them.

Names and formulae ..........................................................................................................................................

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [4]

Type of reaction ............................................................................................................................................. [1]

Equation ........................................................................................................................................................ [1]

c) How would you alter the conditions to increase the yield of these two by-products?

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

d) Suggest a change of reagent to increase the yield of the main product.

....................................................................................................................................................................... [1]

e) Suggest why, when a haloalkane is treated with aqueous potassium hydroxide, an increase in temperaturefavours elimination rather than substitution.

...........................................................................................................................................................................

....................................................................................................................................................................... [2]

TOPIC 13 Questionsheet 4

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OXIDATION OF ALCOHOLS

a) From the following list, select alcohols which are (i) primary, (ii) secondary and (iii) tertiary. Write down theirreference letters and name them.

A CH3CH(OH)CH

2CH

3 B CH

3CH

2CH

2CH

2OH C (CH

3)

2C(OH)CH

3 D (CH

3)

2CHCH

2OH

(i) Primary alcohol(s) ....................................................................................................................................

(ii) Secondary alcohol(s) .................................................................................................................................

(iii) Tertiary alcohol(s) ................................................................................................................................. [4]

TOPIC 13 Questionsheet 5

b) The reactions of alcohols with an acidified dichromate(VI) solution vary according to the alcohol used, andthe way in which the reaction is carried out. Describe the results of the following reactions, giving the namesof the products where appropriate.

(i) Propan-1-ol is boiled under reflux with excess acidified sodium dichromate(VI).

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

(ii) Propan-2-ol is boiled under reflux with excess acidified sodium dichromate(VI).

....................................................................................................................................................................... [2]

(iii) Butan-1-ol is heated whilst acidified sodium dichromate(VI) is added slowly, the product being distilledout as it is formed.

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

(iv) 2-Methylpropan-2-ol is boiled under reflux with excess acidified sodium dichromate(VI).

....................................................................................................................................................................... [1]

(v) With reference to b) (iii), explain why sodium dichromate(VI) is added to butan-1-ol (rather than theother way round) and why it is possible to distil out the product as it is formed.

Why Na2Cr

2O

7 is added to butan-1-ol .......................................................................................................

............................................................................................................................................................... [1]

Why the product can be distilled out .........................................................................................................

............................................................................................................................................................... [2]

Reflux Distillation

A: sodium dichromate(VI)/acid

B: heated butan-1-olB

A

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20

OTHER REACTIONS OF ALCOHOLS

a) The conversion of alcohols to alkenes is often carried out in the presence of concentrated sulfuric acid.

(i) Write an equation for the conversion of ethanol to ethene.

....................................................................................................................................................................... [1]

(ii) What is the optimum temperature for the conversion?

....................................................................................................................................................................... [1]

(iii) What type of reaction is this?

....................................................................................................................................................................... [1]

(iv) What is the role of the sulfuric acid?

....................................................................................................................................................................... [1]

(v) What side reaction (or ‘competing reaction’) may occur which would lower the yield of the alkene?

....................................................................................................................................................................... [1]

(vi) What substance could be used instead of concentrated sulfuric acid to avoid this problem?

....................................................................................................................................................................... [1]

b) Describe, with essential experimental details, how you could prepare samples of the following compounds,starting in each case from butan-1-ol.

(i) 1-Chlorobutane

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

(ii) 1-Bromobutane

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [4]

(iii) Butyl methanoate

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [4]

c) Write an equation for each preparation you have described in b).

(i) ............................................................................................................................................................... [1]

(ii) ............................................................................................................................................................... [1]

(iii) ............................................................................................................................................................... [1]

TOPIC 13 Questionsheet 6

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TEST QUESTION I

Study the following reaction scheme carefully before answering this Questionsheet.

a) Complete the table below to show the structural formulae and names of compounds A – G.

Conc. H2SO

4

Na2Cr

2O

7 + dil. H

2SO

4Tollens’ reagent

Silver mirrorC3H

8O

C3H

6

HBr(aq)

C3H

7Br

NaOH(aq)

C3H

8SO

4

Water

C3H

8O

C3H

6O

BA

CConc. H

2SO

4

D E

F

Na2Cr

2O

7 + dil. H

2SO

4 C3H

6O

G

Tollens’ reagentNo reaction

Compound Structural formula IUPAC name

A

B

C

D

E

F

G

[14]

b) Explain why compound B gives a silver mirror with Tollens’ reagent, although the isomeric compound Gdoes not.

...........................................................................................................................................................................

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [4]

TOPIC 13 Questionsheet 7

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TEST QUESTION II

a) Suppose that, in the laboratory, you were given three unlabelled bottles containing the colourless liquids hex-1-ene,butan-1-ol and hexane. Describe how, by suitable chemical tests, you could conclusively identify each of them.State the reagent (or reagents) you would use, the observation you would expect to make, and write an equation forthe reaction taking place. (If there is no reaction, say so.)

(i) Hex-1-eneReagent(s) ............................................................................................................................................. [1]

Observation ........................................................................................................................................... [1]

Equation ................................................................................................................................................ [1]

(ii) Butan-1-olReagent(s) ............................................................................................................................................. [1]

Observation ........................................................................................................................................... [1]

Equation ................................................................................................................................................ [1]

(iii) HexaneReagent(s) ............................................................................................................................................. [1]

Observation ........................................................................................................................................... [1]

Equation ................................................................................................................................................ [1]

b) It is possible to distinguish between 1-chloropropane, 1-bromopropane and 1-iodopropane by boiling eachone with aqueous sodium hydroxide, then acidifying the mixture with dilute nitric acid and finally addingaqueous silver nitrate. Confirmation is provided by using either dilute or concentrated aqueous ammonia.

(i) What is the purpose of boiling with aqueous sodium hydroxide?

....................................................................................................................................................................... [1]

(ii) What is the purpose of acidifying with dilute nitric acid?

....................................................................................................................................................................... [1]

(iii) On adding aqueous silver nitrate, what would you expect to happen in each case?

From 1-chloropropane .......................................................................................................................... [1]

From 1-bromopropane .......................................................................................................................... [1]

From 1-iodopropane ............................................................................................................................. [1]

(iv) Describe how ammonia solutions can be used to confirm the identities of the halopropanes.

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

TOPIC 13 Questionsheet 8

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TEST QUESTION III

a) An experiment showed that 224 cm3 (measured at s.t.p.) of a gaseous alkene W was able to react with 3.20 gof bromine dissolved in hexane. Calculate the number of carbon – carbon double bonds in one molecule ofW. (1 mol of a gas occupies a volume of 22.4 dm3 at s.t.p.)

...........................................................................................................................................................................

...........................................................................................................................................................................

....................................................................................................................................................................... [3]

b) Alkene W can be converted into butanedioic acid by the following scheme.

W Limited Br2 C

4H

6Br

2

Step A C

4H

8Br

2

Step B C

4H

10O

2

Step C HOOC–CH

2–CH

2–COOH

X Y Z Butanedioic acid

(i) Complete the following table to show the structural formulae and names of compounds X, Y and Z.

Compound Structural formula IUPAC name

X

Y

Z

[6]

(ii) Give the reagents and essential conditions for Steps A, B and C.

Step AReagent ................................................................................................................................................. [1]

Conditions ............................................................................................................................................ [2]

Step BReagent ................................................................................................................................................. [2]

Conditions ............................................................................................................................................ [1]

Step CReagents ............................................................................................................................................... [2]

Conditions ............................................................................................................................................ [1]

c) Suggest a structural formula for compound W.

....................................................................................................................................................................... [1]

TOPIC 13 Questionsheet 9

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TEST QUESTION IV

a) Although, in theory, it should be possible to reduce an alcohol to an alkane, in practice this can seldom bedone directly. Instead, it is necessary to adopt a two-stage route, by first converting the alcohol into either ahaloalkane or an alkene.

Describe how propan-2-ol could be reduced to propane by proceeding (i) via a haloalkane, and (ii) via an alkene.For each stage of each route you should name a reagent, state the conditions and write an equation.

(i) Via a haloalkane

Stage 1

Reagent .................................................................................................................................................. [1]

Conditions ............................................................................................................................................. [1]

Equation ................................................................................................................................................ [1]

Stage 2

Reagent .................................................................................................................................................. [1]

Conditions ............................................................................................................................................. [1]

Equation ................................................................................................................................................ [1]

(ii) Via an alkene

Stage 1

Reagent .................................................................................................................................................. [1]

Conditions ............................................................................................................................................. [1]

Equation ................................................................................................................................................ [1]

Stage 2

Reagent .................................................................................................................................................. [1]

Conditions ............................................................................................................................................. [1]

Equation ................................................................................................................................................ [1]

Alkenes Alcohols Haloalkanes

Alkanes

Stage 1 Stage 1

Theoreticallypossible

Stage 2Stage 2

ReductionO

xida

tion

(Continued...)

TOPIC 13 Questionsheet 10

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TEST QUESTION IV

b) The opposite conversion of that discussed in a), i.e. the oxidation of an alkane to an alcohol, must also becarried out indirectly. Use your knowledge of simple organic compounds to devise a suitable two-stage routefor the conversion of ethane to ethanol. Give the reagent, conditions and equation for each stage.

Stage 1

Reagent .......................................................................................................................................................... [1]

Conditions ..................................................................................................................................................... [1]

Equation ........................................................................................................................................................ [1]

Stage 2

Reagent .......................................................................................................................................................... [1]

Conditions ..................................................................................................................................................... [1]

Equation ........................................................................................................................................................ [1]

TOPIC 13 Questionsheet 10 Continued

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TEST QUESTION VTOPIC 13 Questionsheet 11

a) Name the reagent and conditions required to effect the following conversions;(i)

C C C C HH

HH H H

H H H H

C C C C HH

HH Br H

H H H H

....................................................................................................................................................................... [2](ii)

C C C HH

H H

H H H

C C C HH

BrBr H

H H H

....................................................................................................................................................................... [2]

(iii)

C C C C HH

H H

H H H H

C C C C HH

HH H H

H H H H

....................................................................................................................................................................... [3]

(iv)

C CH

HH

HC C O HH

HH

H H

....................................................................................................................................................................... [3]

b) Complete the reaction scheme below by drawing in the structural formula of the organic compound that ismissing at the start.(i)

u.v. light+ Br

2

C C C HH

BrH H

H

H

C HHH

C C C C HH

BrBr H H

H H H

H

C HH

+ Br2

(ii)

[1]

[1]

12