Alkenes - exam practice
Alkenes
Question 1 of 10
This question is about the structure and properties of alkenes.
Alkenes are unsaturated hydrocarbons.
Explain the meaning of the term unsaturated.
Give the general formula of an alkene.
What is the geometric shape around the carbon atoms involved in the double bond of an alkene?
Explain the term pi-bond in relation to the carbon-carbon double bond of an alkene.
Why are alkenes generally more reactive than alkanes?
This question is about the addition reactions of 2-methylpropene.
2-methylpropene can undergo an addition reaction to form 2-methylpropane.
Suggest suitable reagents and conditions for this reaction.
Name the type of product formed when 2-methylpropene reacts with steam in the presence of an acid catalyst.
Name and outline a mechanism for the reaction between 2-methylpropene and hydrogen bromide to form 2-bromo-2-methylpropane.
Draw the structure of the alternative carbocation that could be formed in the reaction between 2-methylpropene and hydrogen bromide.
Explain why the carbocation you drew in part d) leads to the formation of a minor product.
Alkenes undergo addition reactions to form saturated compounds.
Define the term electrophile.
Complete the mechanism below for the reaction between ethene and HCl.
When 2-methylbut-2-ene reacts with HCl, two products are formed as shown in the diagram below.
Explain which of the two structures shown will be the major product.
Describe the test for an unsaturated hydrocarbon. Include the positive result of the test in your answer.
The alkene hex-3-ene has stereoisomers.
Explain the meaning of the term stereoisomer.
Draw the structures of the E and Z isomers of hex-3-ene.
The alkene 3-methylpent-2-ene is an isomer of hex-3-ene.
Outline a mechanism for the reaction of 3-methylpent-2-ene with HBr to form 3-bromo-3-methylpentane.
Explain why 3-bromo-3-methylpentane is the major product in this reaction.
This question is about the alkene 2-bromopropene.
Three reactions of 2-bromopropene are shown in the diagram below.
Complete the flowchart to show the product formed in each reaction.
Suggest a suitable catalyst for reaction C.
State the name of the process used to produce poly(2-bromopropene) from 2-bromopropene.
Complete the equation below to show the polymerisation of 2-bromopropene.
Give one advantage and one disadvantage of the disposal of poly(2-bromopropene) by incineration.
This question is about the reactions of some alkenes.
Explain why alkenes are generally more reactive than alkanes.
Complete the table below to show the structures of the products formed and the type of each reaction when propene reacts with the following reagents.
The diagram below shows the structure of the polymer polystyrene.
Draw the structure of the monomer used to produce polystyrene.
Waste polymers can be disposed of by combustion.
State one problem with the disposal of polymers containing the element chlorine by combustion.
State two ways, other than combustion, of processing waste polymers.
The diagram below shows the structure of an alkene, X.
Explain why alkene X does not have E/Z stereoisomers.
Alkene Y is a structural isomer of alkene X which does show E/Z stereoisomerism.
Draw the structure of the *Z-*isomer of alkene Y, and name this isomer.
Alkene Y is reacted with steam in the presence of an acid catalyst.
Draw the structure of the product formed.
Pent-2-ene and cyclopentane are structural isomers with the molecular formula C5H10.
Identify a suitable reagent that could be used to distinguish between separate samples of these two hydrocarbons.
State the observations you would make in each case.
2-methylbut-2-ene also has the molecular formula C5H10.
Outline a mechanism for the formation of 2-chloro-2-methylbutane from the reaction between 2-methylbut-2-ene and HCl.
Explain why 2-chloro-3-methylbutane would also be formed in this reaction but in a smaller quantity.
Poly(chloroethene) is commonly known as PVC.
Complete the equation below to show the formation of poly(chloroethene) from chloroethene.
This question is about the alkene but-1-ene.
Explain why the bond angle of the carbon atoms in the double bond of but-1-ene are approximately 120°.
Why does but-1-ene react more readily than butane?
Draw the mechanism for the reaction between but-1-ene and Br2 to form 1,2-dibromobutane.
Explain why the reaction of but-1-ene with HCl results in the formation of two isomeric products.
This question is about unsaturated hydrocarbons.
Define the term unsaturated.
Three reactions of propene are shown below.
Complete the flowchart to show the structures of the products formed.
The alkene pent-2-ene exists as stereoisomers.
Explain the meaning of the term stereoisomers.
Draw the structure of the E-isomer of pent-2-ene.