The structure of butamben is shown. butamben H₂N
- (a)(i)Complete the equation for a reaction in which butamben acts as a base. [1][1]
- (a)(ii)Predict whether butamben is a stronger or weaker base than ammonia. Give a reason for your answer. [1][1]
- (b)Complete the reaction scheme below to show the structural formulae of the products formed when butamben is treated separately with the stated reagent. [3][3]
- (c)(i)State the number of peaks in the spectrum that show a triplet splitting pattern. [1][1]
- (c)(ii)On the diagram of butamben below, circle the protons responsible for the peak or peaks you identified in (c)(i). [1][1]
- (c)(iii)Describe and explain how the proton NMR spectrum of butamben in D₂O would differ from the proton NMR spectrum of butamben in CDCl₃. [2][2]
- (d)The mass spectrum of butamben includes peaks at m/e 92 and 57. Identify the fragments responsible for these peaks. m/e 92 = .......................................................................................................................................................... m/e 57 = .......................................................................................................................................................... [1][1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [1] RNH2 + H+ → RNH3+ OR RNH2 + HCl → RNH3Cl
- [1] weaker AND lone pair of N delocalised into benzene ring
- [3] [Diagrams for each product]
- [1] 2
- [1] CH2 next to ester and terminal CH3 are circled
- [2] • one less peak • the lost peak is NH2 / aryl amine • protons exchange with D OR protons are labile OR valid equation
- [1] C6H4NH2+ and CH3CH2CH2CH2+
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