22. Analytical techniques
A section of Chemistry, 9701
Listing 10 of 112 questions
The combination of mass spectroscopy and NMR spectroscopy provides a powerful method of analysis for organic compounds. The mass spectrum of a compound G contains M and M+1 peaks in the ratio of their heights of 74 : 2.5. Use these data to calculate the number of carbon atoms present in G. Show your working. The NMR spectrum of compound G is shown. δ / ppm Use the Data Booklet and your knowledge of NMR spectroscopy to identify the type of proton responsible for each of the three absorptions.  / ppm type of proton 1.1 2.2 11.8 The addition of D2O causes one of these absorptions to disappear. Explain why this happens and state which absorption is affected. Draw the structural formula of G. Several structural isomers of G exist. Draw the structural formula of an isomer of G with only two absorptions in its NMR spectrum. Use the Data Booklet to suggest where these absorptions would occur. peak  / ppm
9701_s14_qp_43
THEORY
2014
Paper 4, Variant 3
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Use the Data Booklet to draw the structure of the tripeptide Ala-Ser-Gly showing its peptide bonds in full. Ala-Ser-Gly Calculate the relative molecular mass, Mr, of Ala-Ser-Gly. Mr = Electrophoresis can be used to separate mixtures of amino acids and peptides. A mixture of the tripeptide Ala-Ser-Gly and its three constituent amino acids was subjected to electrophoresis in a buffer at pH 11. Draw the structure of serine at pH 11. At the end of the experiment the following results were seen. mixture applied here P G H Q R S I F Identify the components labelled F-I in the above diagram. F G H I Suggest the identities of the species responsible for spot P, spot S. Explain your answers. State the reagents and conditions needed for converting the tripeptide into its three constituent amino acids. Name the type of reaction in .
9701_s16_qp_41
THEORY
2016
Paper 4, Variant 1
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Use the Data Booklet to draw the structure of the tripeptide Ala-Ser-Gly showing its peptide bonds in full. Ala-Ser-Gly Calculate the relative molecular mass, Mr, of Ala-Ser-Gly. Mr = Electrophoresis can be used to separate mixtures of amino acids and peptides. A mixture of the tripeptide Ala-Ser-Gly and its three constituent amino acids was subjected to electrophoresis in a buffer at pH 11. Draw the structure of serine at pH 11. At the end of the experiment the following results were seen. mixture applied here P G H Q R S I F Identify the components labelled F-I in the above diagram. F G H I Suggest the identities of the species responsible for spot P, spot S. Explain your answers. State the reagents and conditions needed for converting the tripeptide into its three constituent amino acids. Name the type of reaction in .
9701_s16_qp_43
THEORY
2016
Paper 4, Variant 3
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Calcitriol is a steroid hormone found in human blood. HO HO OH calcitriol Give the number of primary, secondary and tertiary alcohol groups in one molecule of calcitriol. primary secondary tertiary Give the number of chiral carbon atoms in one molecule of calcitriol. Calcitriol shows geometrical isomerism. Give the number of geometrical isomers of calcitriol, including calcitriol. A sample of calcitriol is treated with an excess of hot, concentrated, acidified potassium manganate(. There are three different carbon‑containing products of this reaction. One of these three products, X, is shown. O O X O O Predict the number of peaks in the carbon-13 NMR spectrum of X. For the carbon‑13 NMR spectrum of X, state the expected chemical shift ranges (δ) of the peaks predicted in and the number of peaks in each range. Predict the number of peaks this compound would show in its proton NMR spectrum. For each of the peaks in the proton NMR spectrum you have identified in give the expected splitting pattern. Explain your reasoning. In addition to the product shown in , two other carbon-containing products are formed when a sample of calcitriol is treated with an excess of hot, concentrated, acidified potassiummanganate(. Of these two other carbon-containing products, identify the product with the smaller molecular mass. Explain how this product is formed. Of these two other carbon-containing products, identify the product with the larger molecular mass by drawing its skeletal formula in the space below.
9701_s18_qp_42
THEORY
2018
Paper 4, Variant 2
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The mass spectrum of compoundX, C5H10O2, is recorded. The peak heights of the M and M+1 peaks are 22.65 and 1.25 respectively. Use these data to show that there are five carbon atoms present in one molecule of X. Show your working.  The mass spectrum has a peak at m/e = 57. Complete the equation to show the fragmentation of X to produce this peak. + +  State the use of TMS and CDCl 3 in NMR spectroscopy. ● TMS ● CDCl 3  The proton NMR spectrum of compound X, C5H10O2, is shown. δ / ppm By considering both the relative peak areas and their δ values, use the Data Booklet to ● deduce the part of the molecule that produces the peak at δ 2.2, ● deduce the part of the molecule that produces the peaks at δ 1.2 and δ 3.5, ● deduce the part of the molecule that produces the peak at δ 4.0.  When reacted with aqueous alkaline iodine, X produces a yellow precipitate. Use this information and your answers to to suggest a structure for X.  Compound W is an ester with the molecular formula C5H10O2. The proton NMR spectrum of W contains only two peaks. The relative areas of these two peaks are in the ratio 9 : 1. Suggest a structure for this ester, W.  Compound V is a carboxylic acid which contains a chiral centre. It also has the molecular formula C5H10O2. Explain what is meant by the term chiral centre. Suggest a structure for V.  
9701_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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The mass spectrum of compoundX, C5H10O2, is recorded. The peak heights of the M and M+1 peaks are 22.65 and 1.25 respectively. Use these data to show that there are five carbon atoms present in one molecule of X. Show your working.  The mass spectrum has a peak at m/e = 57. Complete the equation to show the fragmentation of X to produce this peak. + +  State the use of TMS and CDCl 3 in NMR spectroscopy. ● TMS ● CDCl 3  The proton NMR spectrum of compound X, C5H10O2, is shown. δ / ppm By considering both the relative peak areas and their δ values, use the Data Booklet to ● deduce the part of the molecule that produces the peak at δ 2.2, ● deduce the part of the molecule that produces the peaks at δ 1.2 and δ 3.5, ● deduce the part of the molecule that produces the peak at δ 4.0.  When reacted with aqueous alkaline iodine, X produces a yellow precipitate. Use this information and your answers to to suggest a structure for X.  Compound W is an ester with the molecular formula C5H10O2. The proton NMR spectrum of W contains only two peaks. The relative areas of these two peaks are in the ratio 9 : 1. Suggest a structure for this ester, W.  Compound V is a carboxylic acid which contains a chiral centre. It also has the molecular formula C5H10O2. Explain what is meant by the term chiral centre. Suggest a structure for V.  
9701_s19_qp_43
THEORY
2019
Paper 4, Variant 3
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Z is a molecule which contains the elements carbon, hydrogen and oxygen only. Z contains only alkene and carboxyl functional groups. Complete Table6.1 by describing the observations that occur when two different reagents are added to separate samples of Z. Table 6.1 reagent added to Zobservation Br2Na2CO3 Table6.2 shows the percentage by mass of each element present in Z. Table 6.2 element percentage by mass / % carbon 41.38 hydrogen 3.45 oxygen 55.17 Using the data in Table6.2, demonstrate that the empirical formula of Z is CHO. Show your working.  Fig.6.1 shows the mass spectrum of Z. relative abundance m / e Deduce the molecular formula of Z. Explain your answer by referring to the molecular ion peak in Fig.6.1 and the empirical formula of Z.  Use Fig.6.1 to suggest the formulae of the fragments with m / e peaks at 45 and at 71. m / e 45 m / e 71  Suggest the structure of Z using relevant information from Table6.1, and .  
9701_s22_qp_22
THEORY
2022
Paper 2, Variant 2
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But-2-ene reacts with KMnO4 to form organic product, Y. Y does not react with Na2CO3. A gas is produced when an excess of Na is added to Y. Describe the conditions for the KMnO4 used in the reaction to form Y from but-2-ene. 24.0 cm3 of gas is produced when an excess of Na is added to 0.001 mol of Y, when measured under room conditions. Assume that 1 mol of gas occupies 24.0 dm3 under room conditions. Deduce a possible structure of Y. Explain your answer.  Z contains three types of atom: carbon, hydrogen and a halogen. The mass spectrum of Z is recorded. Fig.5.1 shows a section of the mass spectrum at m/e greater than 63. The fragment at m/e = 64 is the molecular ion peak. 2.2 33.3 relative abundance m/e Deduce the number of carbon atoms present in a molecule of Z using Fig.5.1. Show your working. Deduce which halogen is present in Z using Fig.5.1. Explain your answer. There are also peaks at m/e = 29 and m/e = 49. Suggest the formulae of these fragments. Deduce the name of Z. m/e = 29 m/e = 49 name of Z  
9701_s22_qp_23
THEORY
2022
Paper 2, Variant 3
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State the uses of TMS and D2O in NMR spectroscopy. TMS D2O  The three isomeric ketones with molecular formula C5H10O are: ● pentan-2-one ● pentan-3-one ● 3-methylbutanone. Complete Table 7.1 to show the number of peaks observed in the proton (1H) NMR spectrum and in the carbon-13 NMR spectrum for each compound listed. Table 7.1 ketone number of peaks observed in the proton (1H) NMR spectrum number of peaks observed in the carbon-13 NMR spectrum pentan-2-one pentan-3-one 3-methylbutanone  State all the ketones with molecular formula C5H10O that have: a doublet in their proton (1H) NMR spectrum a singlet in their proton (1H) NMR spectrum.  Cortisone, C21H28O5, is a naturally occurring chemical that contains chiral carbon atoms. CH3 O O O CH3 OH OH cortisone Deduce the number of chiral carbon atoms in one molecule of cortisone. Cortisone is reacted with an excess of NaBH4. State the molecular formula of the organic compound formed. Cortisone is an optically active molecule. Explain what is meant by optically active. 
9701_s22_qp_42
THEORY
2022
Paper 4, Variant 2
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Questions Discovered
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