Gallic acid, C₇H₆O₅, is a naturally occurring aromatic molecule. [Figure 5.1]

1. (a)Gallic acid contains the carboxylic acid and phenol functional groups. State and explain the relative acid strength of these two functional groups.[2]
2. (b)(i)A buffer solution was prepared by dissolving 2.04g of gallic acid in 250cm³ of a solution containing 0.0600 moldm⁻³ of gallate ions, C₇H₅O₅⁻. C₇H₆O₅ ⇌ C₇H₅O₅⁻ + H⁺ Ka = 3.89 × 10⁻⁵ mol dm⁻³ at 298 K Define the term buffer solution.[2]
3. (b)(ii)Calculate the pH of this buffer solution. pH =[3]
4. (b)(iii)Write two equations to show how a solution containing gallic acid, C₇H₆O₅, and gallate ions, C₇H₅O₅⁻, acts as a buffer.[2]
5. (c)(i)Construct an equation for the formation of NO₂⁺ by this method.[1]
6. (c)(ii)Complete the mechanism and draw the intermediate of step 1. Include all relevant charges and curly arrows to show the movement of electron pairs. [Figure 5.2][2]
7. (c)(iii)State the name of the mechanism in (c)(ii).[1]
8. (c)(iv)State the reagents and conditions for step 4.[2]
9. (c)(v)Suggest the structure of compound Q in the box provided. [Figure 5.3][2]
10. (c)(vi)State the reagents and conditions for step 6.[1]
11. (d)(i)State the number of peaks that would be observed in the ¹³C NMR spectrum of gallic acid.[1]
12. (d)(ii)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.[2]

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