12 6 This question is about halogenoalkanes. 2‑chloro‑2‑methylpropane can be hydrolysed by water. The equation for this reaction is (CH3)3CCl + H2O → (CH3)3COH + H+ + Cl− The graph shows how the concentration of 2‑chloro‑2‑methylpropane changes with time during an investigation of this reaction. 0 [(CH3)3CCl] / mol dm–3 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 Time / s 50 100 150 200 (a) Calculate the rate of reaction at 50 s. Show your working on the graph. Include units with your final answer. (3) Rate of reaction at 50 s = .............................................................. (b) What is the classification of the mechanism for the hydrolysis of 2‑chloro‑2‑methylpropane by water? (1) A addition B elimination C free radical substitution D nucleophilic substitution Turn over 13 (c) The letters X, Y and Z refer to three different halogenoalkanes: X 1‑bromobutane Y 2‑bromobutane Z 2‑bromo‑2‑methylpropane 1 cm3 of each of these halogenoalkanes was added to separate test tubes containing 5 cm3 of ethanol and 5 cm3 of aqueous silver nitrate solution in a water bath at 50 °C. (i) State the visible change in the reaction of an ethanol/silver nitrate solution with halogenoalkane X. Include the formula of the compound responsible for this observation. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) The three halogenoalkanes were placed in order of decreasing rate of reaction. Which is the correct sequence? (1) A X, Z, Y B Z, X, Y C Z, Y, X D X, Y, Z 14 (d) Under different conditions, 2‑chloro‑2‑methylpropane can react to produce 2‑methylpropene, (CH3)2C CH2 . (i) State the reagent and conditions needed for this reaction. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) Draw the displayed formula for the repeat unit of a polymer that is made by the polymerisation of 2‑methylpropene, (CH3)2C CH2 . (1) (iii) Draw a mechanism for the addition of hydrogen bromide, HBr, to 2‑methylpropene to form 2‑bromo‑2‑methylpropane. Include curly arrows, and any relevant dipoles and lone pairs. (4) (Total for Question 6 = 14 marks)