AQA Jan 2010 Paper 4 Q4

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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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