CIE Jun 2016 v3 Paper 2 Q4

Answers available below

Acetoin, CH3COCH(OH)CH3, and diacetyl, CH3COCOCH3, are two of the compounds that give butter its characteristic flavour. Their skeletal formulae are shown. PMT HO acetoin diacetyl (a) Give the systematic name for acetoin.[1] (b) Identify the reagents and conditions necessary for the conversion of acetoin into diacetyl.[2] (c) The infra-red spectrum for acetoin is shown. 100 transmittance 50 0 4000 3000 2000 wavenumber / cm1 1500 1000 500 (i) Explain the main features of this spectrum, with reference to the peaks with wavenumbers greater than 1500 cm1.[3]UCLES 2016 9701/23/M/J/16<br /> PMT (ii) State and explain how the infra-red spectrum for diacetyl would differ from the infra-red spectrum for acetoin.[2] (d) If a sample of acetoin is reacted with concentrated sulfuric acid, a single product is formed that does not exhibit stereoisomerism. However, if a sample of acetoin is reacted with HBr, a mixture of a pair of stereoisomers is produced. (i) Give the structural formula of the product of the reaction of acetoin with concentrated sulfuric acid.[1] (ii) Explain why the product in (i) does not exhibit stereoisomerism.[2] (iii) Explain why the product of reaction of acetoin with HBr does exhibit stereoisomerism.[1] (iv) Draw the two stereoisomers from (iii) using the conventional representation.UCLES 2016 9701/23/M/J/16 [2] [Total: 14] [Turn over<br />

Show answer