1 13C NMR

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Oxford Textbook Pages : 512 - 519

CGP Revision Guide Pages : 209 - 211

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Show Specification Ref : 6.3.2a, 6.3.2c, 6.3.2d

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Question 1 / 4

January 2011 QP – Unit 4 AQA Chemistry A-level_question_5 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 2 / 4

January 2012 QP – Unit 4 AQA Chemistry A-level_question_6 do not write outside the box a compound x c h o was analysed by infrared spectroscopy and by proton nuclear magnetic resonance spectroscopy the infrared spectrum of x is shown below use table on the data sheet to help you answer the question transmittance wavenumber cm identify the functional group that causes the absorption at cm in the spectrum mark wmp jan chem b the proton n m r spectrum of x consists of singlet peaks do not write outside the box the table below gives the chemical shift for each of these peaks together with their integration values ppm integration value use table on the data sheet to help you answer the following questions use the chemical shift and the integration data to show what can be deduced about the structure of x from the presence of the following in its proton n m r spectrum b i the peak at mark b ii the peak at mark b iii the peak at mark b iv deduce the structure of x c h o mark turn over wmp jan chem
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Question 3 / 4

January 2013 QP – Unit 4 AQA Chemistry A-level_question_5 do not write outside the box a this question concerns isomers of c h o and how they can be distinguished using n m r spectroscopy the non toxic inert substance tms is used as a standard in recording both h and c n m r spectra a i give two other reasons why tms is used as a standard in recording n m r spectra reason reason marks a ii give the structural formula of tms b the proton n m r spectrum of compound p c h o is represented in figure figure mark ppm the integration trace gave information about the five peaks as shown in figure figure ppm integration ratio wmp jan chem do not write outside the box b i use table on the data sheet figure and figure to deduce the structural fragment that leads to the peak at b ii use table on the data sheet figure and figure to deduce the structural fragment that leads to the peaks at and mark b iii use table on the data sheet figure and figure to deduce the structural fragment that leads to the peaks at and mark b iv deduce the structure of p question continues on the next page mark mark turn over wmp jan chem do not write outside the box c these questions are about different isomers of p c h o c i draw the structures of the two esters that both have only two peaks in their proton n m r spectra these peaks both have an integration ratio of ester ester c ii draw the structure of an optically active carboxylic acid with five peaks in its c n m r spectrum marks mark c iii draw the structure of a cyclic compound that has only two peaks in its c n m r spectrum and has no absorption for c o in its infrared spectrum mark 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 / 4

June 2013 QP – Unit 4 AQA Chemistry A-level_question_7 do not write outside the box a n m r spectroscopy can be used to study the structures of organic compounds compound j was studied using h n m r spectroscopy cl ch ch a c ch ch j ch cl a i identify a solvent in which j can be dissolved before obtaining its h n m r spectrum mark a ii give the number of peaks in the h n m r spectrum of j mark a iii give the splitting pattern of the protons labelled a mark a iv give the iupac name of j mark b compound k was studied using c n m r spectroscopy ch c ch ch ch b i give the number of peaks in the c n m r spectrum of k mark b ii use table on the data sheet to suggest a value of the peak for the carbon labelled b mark b iii give the iupac name of k mark turn over wmp jun chem
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