17.1. Aldehydes and ketones
A subsection of Chemistry, 9701, through 17. Carbonyl compounds
Listing 10 of 304 questions
Lidocaine is used as an anaesthetic. A synthesis of lidocaine is shown in Fig.6.1. X Y NH2 HN W O + Cl Cl O Cl HN O lidocaine N(C2H5)2 reaction 1 reaction 2 (C2H5)2NH W can be formed by reacting HOCH2COOH with an excess of SOCl 2. Write an equation for this reaction. After W and X have reacted together, an excess of CH3COONais added to the reaction mixture. Suggest why. The reaction of W with X, reaction 1, follows an addition–elimination mechanism. Complete the mechanism for the reaction of W with X. Include all relevant curly arrows, lone pairs of electrons, charges and partial charges. Use Ar–NH2 to represent X. O Ar NH2 Cl Cl  (C2H5)2NH reacts with Y in reaction2. Explain why (C2H5)2NH can act as a nucleophile. The purity of lidocaine can be checked using thin-layer chromatography. Ethyl ethanoate is used as the solvent. The Rf values of X and lidocaine are given in Table6.1. Table 6.1 compound Rf X 0.49 lidocaine 0.71 Identify the substances used as the mobile and stationary phases in this thin‑layer chromatography experiment. mobile phase stationary phase  Describe how an Rf value can be calculated. Suggest why the Rf value for X is less than that for lidocaine. The proton (1H) NMR spectrum of lidocaine is shown in Fig.6.2. HN O lidocaine N(C2H5)2 chemical shift / ppm 8.9 7.1 3.0 2.6 1.1 2.3 Table 6.2 environment of proton example chemical shift range δ / ppm alkane –CH3, –CH2–, >CH– 0.9–1.7 alkyl next to C=O CH3–C=O, –CH2–C=O, >CH–C=O 2.2–3.0 alkyl next to aromatic ring CH3–Ar, –CH2–Ar, >CH–Ar 2.3–3.0 alkyl next to electronegative atom CH3–O, –CH2–O, –CH2–Cl 3.2–4.0 attached to alkene =CHR 4.5–6.0 attached to aromatic ring H–Ar 6.0–9.0 aldehyde HCOR 9.3–10.5 alcohol ROH 0.5–6.0 phenol Ar–OH 4.5–7.0 carboxylic acid RCOOH 9.0–13.0 alkyl amine R–NH– 1.0–5.0 aryl amine Ar–NH2 3.0–6.0 amide RCONHR 5.0–12.0 Name the splitting patterns at δ 2.6 and δ 1.1. δ 2.6 δ 1.1  The relative peak area of the peaks at δ 3.0 and δ 2.3 is 1 : 3 respectively. Identify the protons in the 1H NMR spectrum of lidocaine that are responsible for the peaks at the following chemical shift values. δ 7.1 δ 3.0 δ 2.3  Predict the number of peaks in the carbon‑13 (13C) NMR spectrum of lidocaine. 
9701_m22_qp_42
THEORY
2022
Paper 4, Variant 2
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Alkenes undergo an addition reaction with a 1:1 mixture of CO and H2 to form aldehydes. shows the reaction of propene with a 1:1 mixture of CO and H2. propene A B H2 CO CHO CHO and Define addition reaction. Aldehydes A and B are structural isomers. State the type of structural isomerism shown by A and B. Name A. The complete reaction of propene with a 1:1 mixture of CO and H2 produces A and B only. The product mixture contains 96% A and 4% B. Calculate the mass of A produced in this reaction when 5.00 × 103 kg of propene is used. mass of A = kg A and B show reactions typical of aliphatic aldehydes. A undergoes a nucleophilic addition reaction with a mixture of HCN and KCN, forming compound C. Complete the diagram to show the mechanism for this reaction. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. Draw the structure of the organic intermediate. A C O OH CN C H C H C3H7 C3H7 Table 3.1 shows information about three experiments involving B. Complete Table 3.1. Table 3.1 experiment reagents observation with B solution turns from orange to green a silver mirror forms on the sides of the reaction vessel Br2 B, C4H8O, is oxidised by acidified potassium manganate(. Complete the equation for this reaction. Use to represent one atom of oxygen from the oxidising agent. C4H8O + C is a chiral molecule. Circle any chiral centres in the structure of C shown in . C OH C N III C H H C H H C H H C H H When propene reacts with CO and an excess of H2, an alkane and a mixture of alcohols are formed instead. The alcohols are isomers of each other. Suggest the molecular formulae of the alkane and the alcohols that are formed under these conditions. molecular formula of alkane molecular formula of alcohols The reaction of ethene, C2H4, with a 1:1 mixture of CO and H2 is shown in equation 1. equation 1 C2H4+ CO+ H2CH3CH2CHOAt atmospheric pressure a cobalt‑based catalyst is used in this reaction. State and explain the effect of using a catalyst on this reaction. Explain why the yield of CH3CH2CHOincreases when the overall pressure of the reaction mixture is increased. Use the information in Table 3.2 to calculate the enthalpy change, ΔHr, of the reaction in equation 1. equation 1 C2H4+ CO+ H2CH3CH2CHOTable 3.2 compound enthalpy change of formation, ΔHf / kJ mol–1 C2H4+52 CO–111 CH3CH2CHO–187 ΔHr = kJ mol–1 The reaction mixture is cooled to collect CH3CH2CHO as a liquid. Identify all types of van der Waals’ forces that are present between molecules of CH3CH2CHO.
9701_m23_qp_22
THEORY
2023
Paper 2, Variant 2
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Compound Q, heptan-2-one, is found in some blue cheeses. CH3(CH2)4COCH3 compound Q Compound Q may be reduced to R. Compound R may be dehydrated to give two different products, S and T. In the boxes below, draw the structural formulae of R, S, and T. CH3(CH2)4COCH3 R reduce S T dehydrate State the reagents that would be used for each of these reactions in a school or college laboratory. reduction dehydration In the boxes below, write the structural formula of the organic compound formed when Q is reacted separately with each reagent under suitable conditions. If you think no reaction occurs, write 'NO REACTION' in the box. Tollens’ reagent HCN K2Cr2O7 / H+ The fi rst stage of cheese making is to produce 2-hydroxypropanoic acid (lactic acid) from milk. CH3CH(OH)CO2H lactic acid Other than the use of a pH indicator, what reagent could you use to confi rm the presence of some lactic acid in a sample of heptan-2-one? State what observation you would make. reagent observation
9701_s13_qp_23
THEORY
2013
Paper 2, Variant 3
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