2 Mass spectrometry

 

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4.2.4 analytical techniques Page 3

Oxford Textbook Pages : 252 - 255

CGP Revision Guide Pages : 108 - 109

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Show Specification Ref : 4.2.4f, 4.2.4g

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Question 1 / 5

AQA Jun 2013 Paper 2 Q5 do not write outside the box haloalkanes are used in the synthesis of other organic compounds a hot concentrated ethanolic potassium hydroxide reacts with bromo methylbutane to form two alkenes that are structural isomers of each other the major product is methylbut ene a i name and outline a mechanism for the conversion of bromo methylbutane into methylbut ene according to the equation ch chchbrch koh ch c chch kbr h o name of mechanism mechanism a ii draw the displayed formula for the other isomer that is formed marks mark a iii state the type of structural isomerism shown by these two alkenes mark wmp jun chem do not write outside the box b a small amount of another organic compound x can be detected in the reaction mixture formed when hot concentrated ethanolic potassium hydroxide reacts with bromo methylbutane compound x has the molecular formula c h o and is a secondary alcohol b i draw the displayed formula for x mark b ii suggest one change to the reaction conditions that would increase the yield of x mark b iii state the type of mechanism for the conversion of bromo methylbutane into x mark b iv identify one feature of this infrared spectrum of a pure sample of x that may be used to confirm that x is an alcohol you may find it helpful to refer to table on the data sheet transmittance wavenumber cm feature mark turn over wmp jun chem
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Question 2 / 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 3 / 5

AQA Jan 2011 Paper 4 Q5 do not write outside the box atenolol is an example of the type of medicine called a beta blocker these medicines are used to lower blood pressure by slowing the heart rate the structure of atenolol is shown below ch h n oh ch ch ch p ch ch ch q a give the name of each of the circled functional groups labelled j and k on the structure of atenolol shown above functional group labelled j functional group labelled k marks b the h n m r spectrum of atenolol was recorded one of the peaks in the h n m r spectrum is produced by the ch group labelled p in the structure of atenolol use table on the data sheet to suggest a range of values for this peak name the splitting pattern of this peak range of values name of splitting pattern marks c n m r spectra are recorded using samples in solution the h n m r spectrum was recorded using a solution of atenolol in cdcl c i suggest why cdcl and not chcl was used as the solvent mark c ii suggest why cdcl is a more effective solvent than ccl for polar molecules such as atenolol mark wmp jan chem do not write outside the box d the c n m r spectrum of atenolol was also recorded use the structure of atenolol given to deduce the total number of peaks in the c n m r spectrum of atenolol e mark part of the c n m r spectrum of atenolol is shown below use this spectrum and table on the data sheet where appropriate to answer the questions which follow ppm e i give the formula of the compound that is used as a standard and produces the peak at ppm in the spectrum mark e ii one of the peaks in the c n m r spectrum above is produced by the ch group labelled q in the structure of atenolol identify this peak in the spectrum by stating its value mark e iii there are three ch groups in the structure of atenolol one of these ch groups produces the peak at in the c n m r spectrum above draw a circle around this ch group in the structure of atenolol shown below ch ch oh ch ch ch ch ch h n question continues on the next page mark turn over wmp jan chem do not write outside the box f atenolol is produced industrially as a racemate an equimolar mixture of two enantiomers by reduction of a ketone both enantiomers are able to lower blood pressure however recent research has shown that one enantiomer is preferred in medicines f i suggest a reducing agent that could reduce a ketone to form atenolol mark f ii draw a circle around the asymmetric carbon atom in the structure of atenolol shown below ch ch oh ch ch ch ch ch h n mark f iii suggest how you could show that the atenolol produced by reduction of a ketone was a racemate and not a single enantiomer marks f iv suggest one advantage and one disadvantage of using a racemate rather than a single enantiomer in medicines advantage disadvantage marks wmp jan chem turn over for the next question do not write on this page answer in the spaces provided turn over wmp jan chem
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Question 4 / 5

AQA Jun 2011 Paper 4 Q5 do not write outside the box items softened with plasticisers have become an essential part of our modern society compound s shown below is commonly known as phthalic acid esters of phthalic acid are called phthalates and are used as plasticisers to soften polymers such as pvc poly chloroethene cooh cooh a give the iupac name for phthalic acid mark b draw the displayed formula of the repeating unit of poly chloroethene mark question continues on the next page turn over wmp jun chem do not write outside the box c the ester diethyl phthalate dep is used in food packaging and in cosmetics c i complete the following equation showing the formation of dep from phthalic anhydride cooch ch cooch ch dep marks c ii deduce the number of peaks in the c n m r spectrum of dep mark c iii one of the peaks in the c n m r spectrum of dep is at ppm table on the data sheet can be used to identify a type of carbon atom responsible for this peak draw a circle around one carbon atom of this type in the structure below cooch ch cooch ch d the mass spectrum of dep includes major peaks at m z the molecular ion and at m z write an equation to show the fragmentation of the molecular ion to form the fragment that causes the peak at m z mark marks wmp jun chem do not write outside the box e because of their many uses phthalates have been tested for possible adverse effects to humans and to the environment the european council for plasticisers and intermediates is an organisation that represents the manufacturers of plasticisers the text below is taken from a document written by the organisation research demonstrates that phthalates at current and foreseeable exposure levels do not pose a risk to human health or to the environment experimental evidence shows that phthalates are readily biodegradable and do not persist for long in the environment e i hydrolysis of dep in an excess of water was found to follow first order kinetics write a rate equation for this hydrolysis reaction using dep to represent the ester mark e ii suggest what needs to be done so that the public could feel confident that the research quoted above is reliable marks extra space turn over wmp jun chem
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Question 5 / 5

AQA Jun 2016 Paper 4 Q4 do not write outside the box compound x clch cocl is used as a reagent in organic synthesis a the mass spectrum of x contains several molecular ion peaks a i chlorine exists as the isotopes cl and cl in a ratio calculate the m z value of the most abundant molecular ion peak in the mass spectrum of x mark a ii the most abundant fragment ion in the mass spectrum of x has m z draw the displayed formula of this fragment ion mark a iii a molecular ion of x that contains one cl atom and one cl atom undergoes fragmentation to form an ion with m z and one other species write an equation for this fragmentation show which isotope of chlorine is present in each product species marks b one important reaction of x is in the preparation of compound p as shown alcl cl ch c cl ch cl hcl wmp jun chem b i draw the structure of the electrophile formed by the reaction of x with alcl do not write outside the box mark b ii outline the mechanism for the reaction of the electrophile from part b i with benzene in the preparation of p marks c compound q is an alternative product that could be formed when x reacts with benzene cl ch describe how you could distinguish between p and q by a test tube reaction give the reagent used and the observation with each compound marks reagent observation with p observation with q turn over wmp jun chem do not write outside the box d x is also used to make the compound hoch cooh this compound is polymerised to form the polymer known as pga pga is used in surgical sutures stitches d i draw the repeating unit of pga mark d ii production of pga occurs via a cyclic compound two hoch cooh molecules react together to form the cyclic compound and two molecules of water draw the structure of this cyclic compound mark e poly propene is also used in surgical sutures e i draw the repeating unit of poly propene mark wmp jun chem do not write outside the box e ii suggest an advantage of surgical sutures made from pga rather than from poly propene explain your answer marks turn over for the next question turn over wmp jun chem
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