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AS LEVEL CHEMISTRY

2.1.3 ALKENES

ASSESSED HOMEWORK

Answer all questions
Max 63 marks

| Name		…………………………………………………………….. |
| Mark		……../63	……....%	Grade ……… |

1.	Cyclohexene can be converted into cyclohexane.

cyclohexene	cyclohexane
	Suggest suitable reagents and conditions for this reaction.
reagents ...................................................................................................................
conditions .................................................................................................................
[Total 2 marks]

2.	Leaf alcohol reacts with bromine as shown in the equation below.

(i)	State what you would see when bromine reacts with leaf alcohol.
.........................................................................................................................
[1]
(ii)	Complete, with the aid of curly arrows, the mechanism involved in the reaction between leaf alcohol and bromine. Show any relevant dipoles, charges and lone pairs of electrons.

[4]
[Total 5 marks]

3.	(a)	Propan-2-ol can be formed by the hydration of an alkene in the presence of a catalyst.
(i)	Suggest a suitable catalyst for this reaction.
................................................................................................................
[1]
(ii)	This is an electrophilic addition reaction. What is meant by the term electrophile?
................................................................................................................
[1]
(b)	A mechanism for the reaction in (a) is shown below.

(i)	Add ‘curly arrows’ to the mechanism to show the movement of electron pairs in steps 1, 2 and 3.
[3]
(ii)	Suggest, with a reason, the role of the H^+.
................................................................................................................
[1]
[Total 6 marks]

4.	Propene, CH_3CH==CH_2, also reacts with HBr to produce two bromoalkanes that are structural isomers.

Propyne, CH_3CºCH, reacts like propene. It reacts with HBr to give three isomers with molecular formula C_3H_6Br_2.
Draw the three isomers with molecular formula C_3H_6Br_2.
[Total 3 marks]

5.	Polymer A, shown below, can be formed from an alkene.

polymer A
(i)	State the type of polymerisation involved in the formation of polymer A.
.........................................................................................................................
[1]
(ii)	Draw a circle around the repeat unit of polymer A.
[1]
(iii)	Identify the monomer that formed polymer A.
[1]
(iv)	Name polymer A.
.........................................................................................................................
[1]
[Total 4 marks]

6.	But-1-ene can undergo polymerisation. Draw a section of the polymer that can be formed from but-1-ene. Show two repeat units.

[Total 2 marks]

7.	Long chain alkanes, such as nonane, can be cracked into shorter chain alkanes and alkenes.
(i)	Write a balanced equation for the cracking of nonane into heptane and ethene.
.........................................................................................................................
[1]
(ii)	Much of the ethene is then converted into ethanol.
Write a balanced equation for the conversion of ethene into ethanol. State the essential conditions.
equation ..........................................................................................................
[1]
conditions ........................................................................................................
.........................................................................................................................
[2]
[Total 4 marks]

8.	Propene, CH_3CH=CH_2, is an alkene and undergoes an addition reaction with bromine.
(i)	State what you would see when propene reacts with bromine.
.........................................................................................................................
[1]
(ii)	Complete, with the aid of curly arrows, the mechanism involved in the reaction between propene and bromine. Show any relevant dipoles and charges.
H_3C ¾ CH ==CH_2		
	Br
½
Br
[4]
[Total 5 marks]

9.	(a)	Hex-3-ene reacts with Br_2 to produce 3,4-dibromohexane.
	Describe, with the aid of curly arrows, the movement of the electrons in the mechanism.
	Show the intermediate, any relevant dipoles and lone pairs of electrons.

                           Intermediate                 3,4-dibromohexane
[4]
(b)	The mechanism in (a) shows cis-hex-3-ene reacting with Br_2. Trans-hex-3-ene also reacts with Br_2 to produce 3,4-dibromohexane.
(i)	How does the structure of trans-hex-3-ene differ from that of cis-hex-3-ene?

................................................................................................................
................................................................................................................
[1]
(ii)	Explain why both cis and trans hex-3-ene react with Br_2 to produce the same structural isomer.
................................................................................................................
................................................................................................................
................................................................................................................
[1]
[Total 6 marks]

10.	Chloroethene, CH_2CHCl, is polymerised to form poly(chloroethene) commonly known as pvc.
(i)	Draw a section of pvc showing three repeat units. Put a bracket round one repeat unit.

[2]
(ii)	Polymers such as pvc are difficult to dispose of because they are non-biodegradable. Increasingly, they are disposed of by combustion.
State the problem associated with the combustion of polymers such as pvc.
.........................................................................................................................
.........................................................................................................................
[1]
(iii)	State two ways in which chemists are trying to minimise the damage to the environment caused by the disposal of halogenated plastics such as pvc.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[2]
[Total 5 marks]

11.	Body odour often begins with secretions from glands called apocrine glands, which are most numerous in the armpits. Bacteria, which live in the armpits, use these secretions to produce energy and many different waste products. Scientists have isolated one of these waste products, compound E, which is shown below.
	
	Compound E contains two functional groups, one of which is a primary alcohol.
(i)	Name the other functional group and state how you could test for it.
	name of the other functional group .................................................................
	test ..................................................................................................................
	observation .....................................................................................................
[3]
(ii)	Name compound E .........................................................................................
[1]
[Total 4 marks]

12.	(a)	Compound A is a chloroalkene with the percentage composition by mass:
C, 24.7%; H, 2.1%; Cl, 73.2%.
(i)	Calculate the empirical formula of compound A. Show your working.

[2]
(ii)	The relative molecular mass of compound A is 145.5. Show that the molecular formula is C_3H_3Cl_3.

[2]

(b)	Compound A is one of six possible structural isomers of C_3H_3Cl_3 that are chloroalkenes. Two of these isomers are shown below as isomer 1 and isomer 2.

(i)	Draw two other structural isomers of C_3H_3Cl_3 that are chloroalkenes.
[2]
(ii)	Name isomer 1. ......................................................................................
[2]

(c)	All of the isomers in (b) readily polymerise.
(i)	Draw a section of the polymer P that could be formed when isomer 2 polymerises.
	Show two repeat units.
polymer P
[2]
 (ii)	Addition polymers can be difficult to dispose of.
	State two general problems in the disposal of polymers and identify an extra problem when disposing of polymer P.
................................................................................................................
................................................................................................................
................................................................................................................
................................................................................................................
................................................................................................................
[3]
[Total 13 marks]

13.	2-Methylbut-1-ene can be formed by the partial hydrogenation of isoprene.
2-Methylbut-1-ene reacts with Br_2 to produce 1,2-dibromo-2-methylbutane by an electrophilic addition mechanism. The mechanism for the reaction is shown below.

(i)	In step 1, Br_2 behaves as an electrophile. Explain what is meant by the term electrophile.
.........................................................................................................................
[1]
(ii)	Label any relevant dipoles and add ‘curly arrows’ to the mechanism to show the movement of electron pairs in step 1 and in step 2.
[3]
[Total 4 marks]

Paddington Academy