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More Past Papers at: www.pastpapers.org 1 Subject: Chains and Rings Code: 2812 Session: January Year: 2003 Final Mark Scheme 25/1/2003 MAXIMUM MARK Mike Smith Page 1 60 24/02/2003 More Past Papers at: www.pastpapers.org 3 1. (a)(i) B [1] (ii) C [1] (iii) B [1] (iv) A [1] (b) equation C4H9Br + NH3 → C4H9NH2 name: 1-aminobutane/(n-)butylamine/butan-1-amine solvent ethanol/alcohol (c) (i) lone pair (of electrons) donor (ii) and [1] + HBr (or C4H9NH3+Br-) [1] [1] [1] [1] oo o o o xH O oo (iii) C If diagram shows a total of 8 electrons [1] and has a negative charge. [1] only award if the diagram shows 8 electrons unambiguous identification of organic product: 2-methylpropan-1-ol, (CH3)2CHCH2OH H CH3 H C C H H [1] H C H OH [Total : 12] Mike Smith Page 3 24/02/2003 More Past Papers at: www.pastpapers.org 4 2. (a)(i) same molecular formula -different structure [2] same formula -different structure only scores 1 mark (ii) H H Br H Br H H C C C Br H C C C Br H H H H Br C C C Br H H 3 [1] (iii) Br Br C C C H C C C H H H 2 1 Br H H H Br H 4 5 [1] [1] 1,1-dibromopropene [1] (b) (i) H3C H3C H C C C C [1] Br cis Br Br Br [1] H trans (ii) bond angle = 120o ± 4o [1] (iii) Each C in the C=C is not bonded to two different atoms/groups/ or equivalent. [1] Must be 1,3-dibromopropene. [1] (iv) [Total : 11] Mike Smith Page 4 24/02/2003 More Past Papers at: www.pastpapers.org 5 3. (a) (i) H [1] (ii) G [1] (iii) van der Waals/ instantaneous or temporary induced dipoles [1] (b) (i) contains a single/unpaired/lone electron/ not free electron [1] (ii) Br2 → 2 Br• [1] (iii) Homolysis/ homolytic fission/homolytic cleavage [1] (iv) Br• + C5H12 → •C5H11 + HBr [1] •C5H11 + Br2 → C5H11Br [1] (c) + Br• I isomer G, 1 [1] II isomer H, 3 [1] III isomer I, 4 [1] [Total : 11] Mike Smith Page 5 24/02/2003 More Past Papers at: www.pastpapers.org 6 4. (a) (i) C10H20O [1] (ii) alcohol/ OH/ hydroxy(l) [1] secondary [1] (b) or or and 1 mark for each alkene [2] (c) O O or or O C CH3 OOCCH3 or or O2CCH3 OCOCH3 O or full structural formula showing all the atoms 1 mark is available for the ester group showing CH3 bonded via COO to a ring 2 marks for structure as shown [2] [Total : 7] Mike Smith Page 6 24/02/2003 More Past Papers at: www.pastpapers.org 7 5. (a) (i) electrophilic [1] addition [1] (ii) intermediate 1 mark H2C CH2 H2C CH2 + Cl Clδ + Cl δ− curly arrow must be from the pi-bond 1mark 4 marking points: (c) (i) look for 2 Cl + backbone of 4 C’s curly arrow to show hetrolysis of the Cl-Cl bond 1 mark Cl ClH2C CH2Cl curly arrow 1mark dipoles or 1 mark curly arrow from double bond to Cl2, curly arrow showing movement of electrons in the Cl-Cl bond or the dipole in the Cl-Cl, Intermediate carbocation/carbonium ion, Curly arrow from Cl- to intermediate. [4] H Cl H Cl [1] C C C C H H H H (ii) H2C +CH2 Cl “must show end-bonds” general problems: non-biodegradable/ not broken down by bacteria/ do not decompose [1] when burnt toxic fumes are produced [1] [1] specific problem of PVC: also produce HCl/ Cl free radicals when burnt (ii) removal of toxic products or HCl formed during combustion by gas scrubbers/ by dissolving in a spray of alkali/ recycling/feedstock recycling/use energy from combustion for domestic heating/ manufacture biodegradable polymers . [1] [Total : 10] Mike Smith Page 7 24/02/2003 More Past Papers at: www.pastpapers.org 8 6. 3 marks for equations, 2 marks for correctly explaining (in words) each of the 3 processes. 1 mark for correctly explaining (in words) 2 of the processes. Cracking. equation for long chain alkane into shorter chain alkane + alkene. [1] [1] Isomerisation equation for straight chain alkane converted into a branched chain alkane equation could be in the form of: or into anyone of or or Reforming to show straight chain into ring (& must be balanced with appropriate number of H2.) [1] + 4H2 + 3H2 into either of + 2H2 + H2 (All three processes require) the use of heat and/or a catalyst Importance of the products: • • • • • (Allow once) max of 3 marks. [1] [3] more volatile/lower boiling points used in fuels because they burn better/smoother/more efficiently/more efficient fuel additive to petrol reduce knocking/pinking/increase octane number or rating alkenes can form polymers/PVC (see Q5)/alcohols etc 1 mark for quality of written communication to be awarded for clear presentation and SPAG. [1] [Total :8] Mike Smith Page 8 24/02/2003