AQA Jun 2010 Paper 4 Q1

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section a answer all questions in the spaces provided do not write outside the box a reaction mechanism is a series of steps by which an overall reaction may proceed the reactions occurring in these steps may be deduced from a study of reaction rates experimental evidence about initial rates leads to a rate equation a mechanism is then proposed which agrees with this rate equation ethanal dimerises in dilute alkaline solution to form compound x as shown in the following equation ch cho ch ch oh ch cho a chemist studied the kinetics of the reaction at k and then proposed the following rate equation a give the iupac name of compound x rate k ch cho oh mark b the initial rate of the reaction at k was found to be mol dm s when the initial concentration of ethanal was mol dm and the initial concentration of sodium hydroxide was mol dm calculate a value for the rate constant at this temperature and give its units calculation units marks c the sample of x produced consists of a racemic mixture racemate explain how this racemic mixture is formed marks question continues on the next page turn over wmp jun chem do not write outside the box d a three step mechanism has been proposed for this reaction according to the following equations step ch step ch oh ch ch h o ch o ch step ch o ch c h o ch oh ch c oh d i using the rate equation predict which of the three steps is the rate determining step explain your answer rate determining step explanation marks d ii deduce the role of ethanal in step mark wmp jun chem do not write outside the box d iii use your knowledge of reaction mechanisms to deduce the type of reaction occurring in step mark d iv in the space below draw out the mechanism of step showing the relevant curly arrows e in a similar three step mechanism one molecule of x reacts further with one molecule of ethanal the product is a trimer containing six carbon atoms deduce the structure of this trimer marks mark turn over wmp jun chem

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