3 Free radical substitution

 

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4.1.2 alkanes Page 3 - 4

Oxford Textbook Pages : 195 - 197

CGP Revision Guide Pages : 90 - 91

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Show Specification Ref : 4.1.2f, 4.1.2g

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Question 1 / 5

AQA Jan 2011 Paper 2 Q7 do not write outside the box a the reaction of bromine with propane is similar to that of chlorine with methane three steps in the mechanism for the bromination of propane to form bromopropane are shown below step step step br br cid ch ch ch ch ch ch cid br br cid ch ch ch cid hbr ch ch ch br br cid a i name the type of mechanism in this reaction mark a ii give an essential condition for step to occur mark a iii name the type of step illustrated by steps and mark a iv in this mechanism a different type of step occurs in which free radicals combine name this type of step write an equation to show how hexane could be formed from two free radicals in the mechanism of this reaction type of step equation marks a v write an overall equation for the reaction between bromine and propane by the same mechanism to produce octabromopropane c br mark wmp jan chem do not write outside the box b bromine reacts with alkenes even though bromine is a non polar molecule b i explain why bromine molecules react with the double bonds in alkenes marks extra space b ii name the type of mechanism involved in this reaction mark b iii draw the structure of the compound with mr formed when penta diene h c chch ch ch reacts with an excess of bromine c two products are formed when propene reacts with hydrogen bromide draw the structure of the intermediate that leads to the formation of the major product in the reaction of propene with hydrogen bromide give the name of this type of intermediate structure of intermediate mark type of intermediate marks turn over wmp jan chem there are no questions printed on this page do not write on this page answer in the spaces provided wmp jan chem
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Question 2 / 5

AQA Jan 2013 Paper 2 Q7 do not write outside the box the refrigerant r a used in air conditioners is a mixture of two fluoroalkanes pentafluoroethane and difluoromethane a i the mechanism for the reaction of fluorine with either an alkane or a fluoroalkane is similar to that for the reaction of chlorine with methane name the type of mechanism for the reaction of chlorine with methane mark a ii write equations for the following steps in the mechanism for the reaction of fluorine with fluoromethane ch f to form difluoromethane ch f initiation step first propagation step second propagation step a termination step leading to the formation of difluoroethane marks a iii write an overall equation for the reaction of fluorine with ethane to form pentafluoroethane cf chf by this mechanism mark wmp jan chem do not write outside the box b the refrigerant r a ccl cf cl has been banned because of concerns about ozone depletion give the iupac name for ccl cf cl mark c nitrogen monoxide no catalyses the decomposition of ozone into oxygen c i write the overall equation for this decomposition mark c ii use the overall equation to deduce step in the following mechanism that shows how nitrogen monoxide catalyses this decomposition step step o no o no o no o step mark turn over for the next question turn over wmp jan chem
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Question 3 / 5

AQA Jun 2010 Paper 2 Q7 do not write outside the box chlorine is a useful industrial chemical a chlorine gas is used in the manufacture of chlorine containing organic compounds a i write equations for the following steps in the mechanism for the reaction of chlorine with ethane to form chloroethane ch ch cl initiation step first propagation step second propagation step a termination step producing butane marks a ii give one essential condition and name the type of mechanism in this reaction of chlorine with ethane essential condition type of mechanism marks wmp jun chem do not write outside the box b chlorine reacts with cold water b i write an equation for this reaction mark b ii give one large scale application of the use of chlorine in water explain why it is used in this application even though chlorine is very toxic do not include cost example of application explanation of use marks b iii two different chlorine containing compounds are formed when chlorine reacts with cold dilute sodium hydroxide solution one of these compounds is sodium chloride name the other chlorine containing compound formed mark c chlorine is used in the extraction of bromine from seawater c i write the simplest ionic equation for the reaction of chlorine with bromide ions mark c ii explain why bromine has a higher boiling point than chlorine marks turn over wmp jun chem
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Question 4 / 5

AQA Jun 2011 Paper 2 Q7 do not write outside the box a halogens are used to make halogenated organic compounds the refrigerant used in air conditioners is a mixture of fluorinated alkanes these compounds are made by fluorination reactions the mechanism for the reaction of fluorine with an alkane or with a fluoroalkane is a free radical substitution similar to the reaction of chlorine with methane a i write the overall equation for the reaction of fluorine with methane to form trifluoromethane chf mark a ii write equations for the following steps in the mechanism for the reaction of fluorine with trifluoromethane chf to form tetrafluoromethane cf initiation step first propagation step second propagation step a termination step leading to the formation of hexafluoroethane marks wmp jun chem do not write outside the box b chlorofluorocarbons cfcs were used as refrigerants in the upper atmosphere ultra violet radiation breaks bonds in the cfcs to produce a reactive intermediate that catalyses the decomposition of ozone b i an example of a cfc is trichloro difluoroethane draw the displayed formula of this cfc mark b ii identify a bond in a cfc that is broken by ultra violet radiation to produce a reactive intermediate give the name of this reactive intermediate that catalyses the decomposition of ozone write an overall equation for this decomposition of ozone bond broken name of the reactive intermediate overall equation marks turn over for the next question turn over wmp jun chem
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Question 5 / 5

AQA Jun 2012 Paper 2 Q6 do not write outside the box chloromethanes such as dichloromethane and trichloromethane are produced in industry as they have many uses trichloromethane has been used in the manufacture of the refrigerant chlorodifluoromethane a chlorine can react with dichloromethane ch cl to form trichloromethane chcl a i write an equation for each of the following steps in the mechanism for this reaction initiation step first propagation step second propagation step marks a ii give one essential condition for this reaction and name the type of mechanism essential condition type of mechanism marks question continues on the next page turn over wmp jun chem do not write outside the box b an organic product x with mr is obtained when chlorine reacts with trichloromethane b i write an equation for the overall reaction of chlorine with trichloromethane to form x by the same mechanism as that outlined in part a i mark b ii the following infrared spectrum was obtained for a sample of x produced in this reaction transmittance wavenumber cm use this infrared spectrum to explain why it is possible to deduce that this sample of x contains no trichloromethane you may find it helpful to refer to table on the data sheet marks extra space wmp jun chem do not write outside the box c explain with the aid of equations and the intermediates that form in the ozone layer why the european union has banned the use of chlorodifluoromethane chclf as a refrigerant marks extra space d the compound tetrafluoropropene is the refrigerant used in all new car air conditioners d i draw the displayed formula for tetrafluoropropene d ii give one reason why tetrafluoropropene is a more environmentally acceptable refrigerant than chlorodifluoromethane mark mark turn over wmp jun chem
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