11177 14 The buttery flavour of butterscotch is due to the presence of diacetyl, CH3COCOCH3. (a) Suggest the IUPAC name for diacetyl. [1] (b) Diacetyl can be made from the corresponding alcohol. (i) Write an equation for the reaction, using [O] to represent the oxidising agent. [2] (ii) State the reagent and the condition required for this reaction. [2] 11177 [Turn over (iii) Diacetyl is a liquid at room temperature with a melting point of −3 °C and a boiling point of 88 °C. The diacetyl obtained in this reaction contains water. Explain how you would use fractional distillation to purify the diacetyl. Describe how you would dry the diacetyl. State how you would use infrared spectroscopy to confirm the diacetyl is pure. In this question you will be assessed on using your written communication skills including the use of specialist scientific terms. [6] 11177 (c) Diacetyl may react with one or two molecules of 2,4-dinitrophenylhydrazine. (i) Write the equation for the reaction of diacetyl with one molecule of 2,4-dinitrophenylhydrazine. [2] (ii) Describe the appearance of the product. [1] (iii) Explain why the melting point of the product formed with one molecule of 2,4-dinitrophenylhydrazine would differ from that formed from the reaction with two molecules of 2,4-dinitrophenylhydrazine. [2] BLANK PAGE DO NOT WRITE ON THIS PAGE (Questions continue overleaf) 11177 [Turn over