22.1. Infrared spectroscopy
A subsection of Chemistry, 9701, through 22. Analytical techniques
Listing 10 of 14 questions
Compound S is used in food flavourings. A possible synthesis of S is shown in . CN HBr reaction 1 KCN in ethanol reaction 2 H+reaction 3 P R COOH S Q P, Q, R and S show stereoisomerism. Complete Table 4.1 by identifying with a tick (3) the type of stereoisomerism that each molecule shows. The type of stereoisomerism shown by Q is given. Table 4.1 P Q R S geometrical isomerism optical isomerism Give the structural formula of Q. Name the mechanism in reaction 2. Complete the equation for reaction 3. R is represented as C4H9CN. C4H9CN + Compounds S and T react to form organic compound U, which has a single functional group. COOH S + + H2O T U Table 4.2 shows some data from the mass spectrum of U. Table 4.2 peak relative abundance M+ 7.2 [M+1]+ 0.55 Use the data from Table 4.2 to show that U contains 7 carbon atoms. Show your working. shows the infrared spectrum of U. wavenumber / cm–1 transmittance / % Table 4.3 bond functional groups containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=C aromatic compound, alkene 1500–1680 C=O amide carbonyl, carboxyl ester 1640–1690 1670–1740 1710–1750 C≡N nitrile 2200–2250 C–H alkane 2850–2950 N–H amine, amide 3300–3500 O–H carboxyl hydroxy 2500–3000 3200–3650 Use and Table 4.3 to identify the functional group present in U. Explain your answer fully. functional group explanation T also has a single functional group. Use the information in and your answer to to identify T and U. Draw the structures of T and U in the boxes. T U
9701_m24_qp_22
THEORY
2024
Paper 2, Variant 2
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A sample of but-2-enoic acid, CH3CH=CHCOOH, is analysed using infrared spectroscopy. The infrared spectrum shows a broad peak in the range 2500–3000 cm–1. bond functional groups containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=O amide carbonyl, carboxyl ester 1640–1690 1670–1740 1710–1750 C=C aromatic compound, alkene 1500–1680 C–H alkane 2850–2950 O–H carboxyl hydroxy 2500–3000 3200–3600 N–H amine, amide 3300–3500 C≡N nitrile 2200–2250 Which bond is responsible for this peak?
9701_s24_qp_13
MCQ
2024
Paper 1, Variant 3
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Compound W has molecular formula C4H10O. It contains only one functional group. Table 5.1 shows the two peaks with the greatest m / e values in the mass spectrum of W. Table 5.1 m / e relative abundance x Calculate the relative abundance, x, of the peak at m / e = 75 using the information from Table 5.1. x = The mass spectrum of W also shows peaks at m / e = 29 and m / e = 59. Suggest the molecular formulae of these fragments. m / e = 29 m / e = 59 A sample of W, C4H10O, is heated under reflux with an excess of acidified K2Cr2O7 until there is no further reaction. Only one organic product, X, is present in the mixture at the end of the reaction. shows the infrared spectrum of W. wavenumber / cm–1 transmittance / % A shows the infrared spectrum of X. wavenumber / cm–1 transmittance / % B Table 5.2 bond functional groups containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=C aromatic compound, alkene 1500–1680 C=O amide carbonyl, carboxyl ester 1640–1690 1670–1740 1710–1750 C≡N nitrile 2200–2250 C–H alkane 2850–2950 N–H amine, amide 3300–3500 O–H carboxyl hydroxy 2500–3000 3200–3650 Absorption A is shown in . Absorption B is shown in . Complete Table 5.3 using the information given in , and Table 5.2. Table 5.3 absorption bond functional group containing the bond A B , , Use the information in and to draw the structure of X in the box in . C4H10O W X acidified K2Cr2O7 + Y is a structural isomer of W. Both W and Y produce colourless bubbles when sodium is added to them. Y does not react when heated with acidified K2Cr2O7. Y does not react when warmed with alkaline I2. Name the functional group present in Y. Complete the equation to describe the reaction of W or Y with sodium. C4H10O + Na Draw the structure of Y. , ,
9701_s24_qp_22
THEORY
2024
Paper 2, Variant 2
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Questions Discovered
14