A Level Chemistry 9701/23/M/J/20 Q4
4 Hexane, C6H14, is a colourless liquid. Two test-tubes contain equal amounts of hexane. 1cm3 of bromine, Br2(aq), is added to both test-tubes. One test-tube is kept in the dark and the other is exposed to sunlight.The table describes the appearance of each test-tube after one hour.
(a) The test-tube in the dark is kept cool and is not exposed to ultraviolet light. Explain the observations for the test-tube kept in the dark.
(b) In sunlight, bromine reacts with hexane by a mechanism which occurs via a series of steps.
(i) State the name of the mechanism of the reaction that occurs.
(ii) Give an equation which shows a propagation step in this reaction in which hexane produces •C6H13.
(iii) Give an equation which shows a propagation step in this reaction that produces 1-bromohexane.
(iv) Give an equation which shows a termination step in this reaction that produces 1-bromohexane.
(c) A and B are different straight chain alkenes with molecular formula, C6H12.
A does not show stereoisomerism.
A reacts with potassium manganate(VII) to form hexane-1,2-diol.
(i) Draw the structural formula of A.
(ii) State the conditions needed for this reaction of A.
(d) B reacts with hydrogen gas in the presence of a platinum catalyst to produce hexane.
(i) Name the type of reaction occurring.
(ii) In terms of σ and π bonds, describe any similarities and differences in the type of carbon-carbon bonds in B and the type of carbon-carbon bonds in hexane.