Edexcel Jan 2012 Paper 1 Q26 (with explained solutions) |

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Edexcel Jan 2012 Paper 1 Q26

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PMT 26(cid:3) (cid:11)(cid:68)(cid:12)(cid:3)(cid:55)(cid:75)(cid:72)(cid:3)(cid:68)(cid:79)(cid:78)(cid:72)(cid:81)(cid:72)(cid:86)(cid:3)(cid:75)(cid:68)(cid:89)(cid:72)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:74)(cid:72)(cid:81)(cid:72)(cid:85)(cid:68)(cid:79)(cid:3)(cid:73)(cid:82)(cid:85)(cid:80)(cid:88)(cid:79)(cid:68)(cid:3)(cid:38)nH2n. However, a compound with this (cid:74)(cid:72)(cid:81)(cid:72)(cid:85)(cid:68)(cid:79)(cid:3)(cid:73)(cid:82)(cid:85)(cid:80)(cid:88)(cid:79)(cid:68)(cid:3)(cid:76)(cid:86)(cid:3)(cid:81)(cid:82)(cid:87)(cid:3)(cid:81)(cid:72)(cid:70)(cid:72)(cid:86)(cid:86)(cid:68)(cid:85)(cid:76)(cid:79)(cid:92)(cid:3)(cid:68)(cid:81)(cid:3)(cid:68)(cid:79)(cid:78)(cid:72)(cid:81)(cid:72)(cid:17)(cid:3)(cid:3)(cid:54)(cid:88)(cid:74)(cid:74)(cid:72)(cid:86)(cid:87)(cid:3)(cid:90)(cid:75)(cid:92)(cid:3)(cid:87)(cid:75)(cid:76)(cid:86)(cid:3)(cid:76)(cid:86)(cid:3)(cid:86)(cid:82)(cid:17) (1)(cid:3) (cid:11)(cid:69)(cid:12)(cid:3)(cid:42)(cid:76)(cid:89)(cid:72)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:72)(cid:84)(cid:88)(cid:68)(cid:87)(cid:76)(cid:82)(cid:81)(cid:15)(cid:3)(cid:88)(cid:86)(cid:76)(cid:81)(cid:74)(cid:3)(cid:86)(cid:78)(cid:72)(cid:79)(cid:72)(cid:87)(cid:68)(cid:79)(cid:3)(cid:73)(cid:82)(cid:85)(cid:80)(cid:88)(cid:79)(cid:68)(cid:72)(cid:15)(cid:3)(cid:73)(cid:82)(cid:85)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:85)(cid:72)(cid:68)(cid:70)(cid:87)(cid:76)(cid:82)(cid:81)(cid:3)(cid:82)(cid:73)(cid:3)(cid:83)(cid:85)(cid:82)(cid:83)(cid:72)(cid:81)(cid:72)(cid:3)(cid:90)(cid:76)(cid:87)(cid:75)(cid:3)(cid:72)(cid:68)(cid:70)(cid:75)(cid:3)(cid:82)(cid:73)(cid:3) the following. (i) Hydrogen: (ii) Hydrogen bromide to form the major product: (c) Give the mechanism for the reaction of propene with hydrogen bromide, HBr, to form the major product. (1) (2) (3) (Total for Question 26 = 7 marks) TOTAL FOR SECTION B = 60 MARKS TOTAL FOR PAPER = 80 MARKS *P39295A02324* 23<br />

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Question Number 26(a) Question Number 26(b)(i) Acceptable Answers Reject Mark (CnH2n could be a) ring / cyclic (compound) ALLOW identification of any specific cyclic compound (e.g. cyclohexane) IGNORE any reference to fewer hydrogen atoms Acceptable Answers Reject Mark 6CH0101 1201<br />
Question Number 26(c) Acceptable Answers Reject Mark H3C Br (:)Br H3C H3C Br H3C HH H + Br carbocation (1) both arrows (1) attack of bromide ion (1) First mark: Curly arrow from C=C to H (in H-Br) AND curly Full + arrow from bond in H-Br to the Br andIGNORE polarity of HBr even if incorrect (1) charges on HBr Second mark: Extra / Structure of correct secondary carbocation (1) spare bond dangling from the C+ carbon Third mark: Curly arrow from anywhere on the bromide ion towards the C+ on the carbocation don NOTE: The bromide ion must have a full negative charge, but the lone pair of electrons on the Br bromide ion NEED NOT be shown instead of Br NOTE: A correct mechanism leading to the formation of 1-bromopropane scores the first and third marks only (so max (2)) Skeletal formulae can be used 6CH0101 1201<br />
If but-2-ene is the starting alkene, only 3rd mark can be awarded If but-1-ene is the starting alkene, 2nd and 3rd marks can be awarded If single-headed arrows used throughout but all else correct, then max (2) can be awarded for mechanism TOTAL FOR SECTION B = 60 MARKS TOTAL FOR PAPER = 80 MARKS 6CH0101 1201<br />

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