3 Nucleophilic addition

 

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6.1.2 carbonyls Page 2

Oxford Textbook Pages : 457 - 459

CGP Revision Guide Pages : 180 - 181

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Show Specification Ref : 6.1.2b, 6.1.2c

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Question 1 / 5

AQA Jan 2010 Paper 4 Q4 areas outside the box will not be scanned for marking two isomeric ketones are shown below ch c ch ch ch ch ch c ch ch o q o r a name and outline a mechanism for the reaction of compound q with hcn and name the product formed name of mechanism mechanism name of product marks wmp jan chem b some students were asked to suggest methods to distinguish between isomers q and r areas outside the box will not be scanned for marking one student suggested testing the optical activity of the products formed when q and r were reacted separately with hcn by considering the optical activity of these products formed from q and r explain why this method would not distinguish between q and r marks extra space c other students suggested using mass spectrometry and the fragmentation patterns of the molecular ions of the two isomers to distinguish between them they predicted that only one of the isomers would have a major peak at m z in its mass spectrum so that this method would distinguish between q and r c i identify the isomer that has a major peak at m z in its mass spectrum mark c ii write an equation for the fragmentation of the molecular ion of this isomer to form the species that produces the peak at m z marks c iii predict the m z value of a major peak in the mass spectrum of the other isomer mark turn over wmp jan chem
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Question 2 / 5

AQA Jan 2011 Paper 4 Q6 section b answer all questions in the spaces provided do not write outside the box many synthetic routes need chemists to increase the number of carbon atoms in a molecule by forming new carbon carbon bonds this can be achieved in several ways including reaction of an aromatic compound with an acyl chloride reaction of an aldehyde with hydrogen cyanide a consider the reaction of benzene with ch ch cocl a i write an equation for this reaction and name the organic product identify the catalyst required in this reaction write equations to show how the catalyst is used to form a reactive intermediate and how the catalyst is reformed at the end of the reaction marks extra space wmp jan chem do not write outside the box a ii name and outline a mechanism for the reaction of benzene with this reactive intermediate marks extra space question continues on the next page turn over wmp jan chem do not write outside the box b consider the reaction of propanal with hcn b i write an equation for the reaction of propanal with hcn and name the product marks extra space b ii name and outline a mechanism for the reaction of propanal with hcn marks extra space wmp jan chem do not write outside the box b iii the rate determining step in the mechanism in part b ii involves attack by the nucleophile suggest how the rate of reaction of propanone with hcn would compare with the rate of reaction of propanal with hcn explain your answer marks extra space turn over for the next question turn over wmp jan chem
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Question 3 / 5

AQA Jun 2013 Paper 4 Q5 do not write outside the box lactic acid ch ch oh cooh is formed in the human body during metabolism and exercise this acid is also formed by the fermentation of carbohydrates such as sucrose c h o a i give the iupac name for lactic acid mark a ii write an equation for the formation of lactic acid from sucrose and water mark b a molecule of lactic acid contains an asymmetric carbon atom the lactic acid in the body occurs as a single enantiomer a racemic mixture racemate of lactic acid can be formed in the following two stage synthesis ch c o stage hcn ch c cn oh stage ch c cooh oh b i name and outline a mechanism for stage name of mechanism mechanism marks wmp jun chem do not write outside the box b ii give the meaning of the term racemic mixture racemate mark b iii explain how you could distinguish between a racemic mixture racemate of lactic acid and one of the enantiomers of lactic acid marks c a mixture of lactic acid and its salt sodium lactate is used as an acidity regulator in some foods an acidity regulator makes sure that there is little variation in the ph of food c i write an equation for the reaction of lactic acid with sodium hydroxide mark c ii the acid dissociation constant ka for lactic acid has the value mol dm at k calculate the ph of an equimolar solution of lactic acid and sodium lactate marks question continues on the next page turn over wmp jun chem do not write outside the box c iii suggest an alternative name for the term acidity regulator explain how a mixture of lactic acid and sodium lactate can act as a regulator when natural processes increase the acidity in some foods name explanation marks extra space d the cup shown is made from pla poly lactic acid pla is the condensation polymer formed from lactic acid the polymer is described as biodegradable and compostable compostable material breaks down slowly in contact with the moist air in a garden bin this produces compost that can be used to improve soil the manufacturers stress that pla cups differ from traditional plastic cups that are neither biodegradable nor compostable d i draw a section of pla that shows two repeating units marks wmp jun chem do not write outside the box d ii name the type of condensation polymer in pla mark d iii an intermediate in the production of pla is a cyclic compound c h o that is formed from two pla molecules draw the structure of this cyclic compound d iv traditional non biodegradable plastic cups can be made from poly phenylethene commonly known as polystyrene draw the repeating unit of poly phenylethene mark mark d v the manufacturers of pla claim that the material will break down to compost in just weeks suggest one reason why pla in landfill may take longer than weeks to break down mark turn over wmp jun chem
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Question 4 / 5

AQA Jun 2013 Paper 4 Q8 section b do not write outside the box answer all questions in the spaces provided a this question is about the primary amine ch ch ch nh the amine ch ch ch nh reacts with ch cocl name and outline a mechanism for this reaction give the iupac name of the organic product marks wmp jun chem do not write outside the box b isomers of ch ch ch nh include another primary amine a secondary amine and a tertiary amine b i draw the structures of these three isomers label each structure as primary secondary or tertiary b ii use table on the data sheet to explain how you could use infrared spectra in the range outside the fingerprint region to distinguish between the secondary amine and the tertiary amine marks marks question continues on the next page turn over wmp jun chem do not write outside the box c the amine ch ch ch nh can be prepared by two different routes route a is a two stage process and starts from ch ch br route b is a one stage process and starts from ch ch ch br c i identify the intermediate compound in route a give the reagents and conditions for both stages in route a and the single stage in route b marks c ii give one disadvantage of route a and one disadvantage of route b marks wmp jun chem
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Question 5 / 5

AQA Jun 2014 Paper 4 Q5 do not write outside the box a the carbonyl compound ch ch cho reacts very slowly with hcn name and outline a mechanism for the reaction of ch ch cho with hcn marks name of mechanism mechanism b the reaction in question a produces a pair of enantiomers b i draw the structure of each enantiomer to show how they are related to each other marks wmp jun chem b ii state and explain how you could distinguish between the two enantiomers do not write outside the box marks c give the iupac name of the product of the reaction in question a mark d in practice kcn rather than hcn is added to the carbonyl compound given that ka for hcn mol dm suggest why the reaction with hcn is very slow marks question continues on the next page turn over wmp jun chem do not write outside the box e acrylic fibres are used as a substitute for wool acrylics are copolymers of acrylonitrile with other compounds acrylonitrile is the common name for the following compound e i acrylonitrile can be formed from propene h c ch c n write an equation for the reaction of propene with ammonia and oxygen to form acrylonitrile and one other product mark e ii the term copolymer is used to describe the product obtained when two or more different monomers form a polymer draw the repeating unit of the acrylic copolymer that contains acrylonitrile monomer and chloroethene monomer mark e iii name the type of polymerisation involved in question e ii mark wmp jun chem turn over for the next question do not write on this page answer in the spaces provided turn over wmp jun chem
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