18. Carboxylic acids and derivatives
A section of Chemistry, 9701
Listing 10 of 202 questions
Gallic acid, C7H6O5, is a naturally occurring aromatic molecule. gallic acid HO HO HO O OH Gallicacid contains the carboxylicacid and phenol functional groups. State and explain the relative acid strength of these two functional groups. A buffer solution was prepared by dissolving 2.04 g of gallic acid in 250 cm3 of a solution containing 0.0600 mol dm–3 of gallate ions, C7H5O5 –. C7H6O5 C7H5O5 – + H+ Ka = 3.89 × 10–5 mol dm–3 at 298 K Define the term buffer solution. Calculate the pH of this buffer solution.  pH = Write two equations to show how a solution containing gallic acid, C7H6O5, and gallate ions, C7H5O5 –, acts as a buffer. CompoundK is used as the starting material in a synthesis of gallic acid. A student suggested the first two steps of the synthesis could be as shown. K COOH NH2 L COOH NO2 NH2 concentrated HNO3 and concentrated H2SO4 step 1 concentrated HNO3 and concentrated H2SO4 step 2 M COOH NO2 O2N NH2 Nitronium ions, NO2 +, are generated by the reaction between concentrated sulfuricacid and concentrated nitricacid. Construct an equation for the formation of NO2 + by this method. Complete the mechanism and draw the intermediate of step1. Include all relevant charges and curly arrows to show the movement of electron pairs. COOH NH2 NO2 L + H+ intermediate +  State the name of the mechanism in . CompoundM is converted into compoundP as shown. CH3CH2OH and H2SO4 step 3 step 4 M COOH NO2 O2N NH2 N COOC2H5 NO2 O2N NH2 P COOC2H5 NH2 H2N NH2 State the reagents and conditions for step4. P reacts with an excess of sodiumnitrite, NaNO2, and dilute HCl at 5 °C to form compoundQ, C9H7N6O2Cl 3. CompoundQ is then converted into gallicacid. Q C9H7N6O2Cl 3 P COOC2H5 NH2 H2N NH2 an excess of NaNO2 and dilute HCl at 5 °C step 5 step 6 gallic acid HO HO HO O OH  Suggest the structure of compoundQ in the box provided. State the reagents and conditions for step6. State the number of peaks that would be observed in the 13C NMR spectrum of gallicacid. gallic acid HO HO HO O OH The proton NMR spectrum of gallic acid dissolved in D2O is recorded. ● ● Predict the number of peaks observed and any expected splitting pattern. ● ● State the expected chemical shift range (δ) of each peak predicted. 
9701_m20_qp_42
THEORY
2020
Paper 4, Variant 2
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Fumaric acid is a naturally occurring dicarboxylic acid. HO2C CO2H fumaric acid Identify the products of the reaction between fumaricacid and an excess of hot, concentrated, acidified manganate(. Fumaricacid can form addition and condensation polymers. Draw the repeat unit of the addition polymer poly(fumaric acid).  Draw the repeat unit of the polyester formed when fumaric acid reacts with ethane‑1,2‑diol, (CH2OH)2. The ester bond should be shown fully displayed.  Explain why polyesters normally biodegrade more readily than polyalkenes. Fumaricacid reacts with cold, dilute, acidified manganate(to form compoundP. P CO2H OH OH HO2C Only three stereoisomers of P exist. One of the stereoisomers is shown. CO2H OH OH H H HO2C Complete the three-dimensional diagrams in the boxes to show the other two stereoisomers of P. HO2C HO2C  The enzyme fumarase catalyses the reaction of fumarate ions, C4H2O4 2–, with water to form malate ions, C4H4O5 2–. C4H2O4 2– + H2O C4H4O5 2– Describe, with the aid of a suitably labelled diagram, how an enzyme such as fumarase can catalyse a reaction.  
9701_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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