M. (a) Functional group (isomerism) (b) M Tollens (reagent) (Credit ammoniacal silver nitrate a description of making Tollens ) (Ignore either AgNO or [Ag(NH ) 2 + ] or the silver mirror test on their own, but mark M2 and M) M Fehling s (solution) or Benedict s solution (Ignore Cu 2+ (aq) or CuSO 4 on their own, but mark on to M2 and M) M2 silver mirror M2 Red solid/precipitate (Credit orange or brown solid) black solid/precipitate (NOT silver precipitate) M (stays) colourless or no change or no reaction M (stays) blue or no change or no reaction Mark on from an incomplete/incorrect attempt at the correct reagent, penalising M No reagent, CE=0 Allow the following alternatives M (acidified) potassium dichromate(vi) (solution) M2 (turns) green M (stays) orange/no change M (acidified) potassium manganate(vii) (solution) M2 (turns) colourless M (stays) purple/no change For M Ignore nothing (happens) Ignore no observation (c) (Both have) C=O a carbonyl (group) (d) (i) (Free-) radical substitution ONLY Penalise (free) radical mechanism (ii) Initiation Page 2
Cl 2 2Cl Penalise absence of dot once only. First propagation Cl + CH CH 2CH CH 2CH 2CH + HCl C H 8 Penalise incorrect position of dot on propyl radical once only. Penalise C H 7 once only Second propagation Cl 2 + CH 2CH 2CH CH CH 2CH 2Cl + Cl C H 7Cl Accept CH CH 2CH 2 with the radical dot above/below/to the side of the last carbon. Termination (must make C 6H 4) 2 CH 2CH 2CH C 6H 4 or CH CH 2CH 2CH 2CH 2CH Use of the secondary free radical might gain of the four marks 4 (e) M r = 44.0652 (for propane) M r = 4.98982 (for carbon dioxide) Mark independently M a correct value for both of these M r values. M2 a statement or idea that two peaks appear (in the mass spectrum) two molecular ions are seen (in the mass spectrum). 2 [2] M2. (a) (i) M pentan--one only M2 CH CH 2CH 2COCH (insist on C=O being drawn out) (penalise use of C H 7) Page
(ii) aldehyde (CH ) 2CHCH 2CHO ketone (CH ) 2CHCOCH (insist on a clear structure for the C=O of the functional groups, but do not be too harsh on the vertical bonds between carbon atom son this occasion) (If both structures correct, but wrong way around, award one mark) (ignore names) (b) (i) CH CH 2CH 2CH 2CHO + [O] CH CH 2CH 2CH 2COOH (accept C 4H 9CHO going to C 4H 9COOH) (insist on a balanced equation for example do not credit [O] over the arrow alone) (ii) pentanoic acid (credit pentan oic acid) (c) (i) CH CH 2CH 2CH 2CH 2OH pentan ol (If both a structure and a formula are given, credit either correct one of these provided the other is a good, if imperfect, attempt) (ii) Primary (credit o or ) [8] M.(a) Eliminate / reduce fire risk; Allow ethanol flammable / burns / combusts. Page 4
(b) Orange to green; Need full colour change to score mark. [2] M4. (a) M Displayed formula for butan-2-ol M2 Alcohol X is M displayed formula must have all bonds drawn out, including the O H but ignore angles Penalise sticks M2 structure must be clearly identifiable as 2-methylpropan-2-ol and may be drawn in a variety of ways. M Alcohol Y is named (2)-methylpropan--ol ONLY M must be correct name, but ignore structures (b) M The infrared spectrum shows an absorption/peak in the range 20 to 550 (cm )(which supports the idea that an alcohol is present) In M, allow the words dip, spike, low transmittance and trough as alternatives for absorption. M2 Reference to the fingerprint region or below 500 (cm ) M Match with or same as known sample/database spectra Check the spectrum to see if alcohol OH is labelled and credit. M2 Run infrared spectra (of the alcohols) M Find which one matches or is the same as this spectrum. Page 5
(c) M balanced equation C 6H 2O 6 CH CH 2CH 2CH 2OH + 2CO 2 + H 2O or C 4H 9OH Or multiples for M and M In M and M penalise use of C 4H 0O or butan-2-ol once only M2 Any one from excess/adequate/sufficient/correct amount of/enough/plenty/ a good supply of oxygen or air good mixing of the fuel and air/oxygen For M2, do not accept simply oxygen or air alone Ignore reference to temperature M CH CH 2CH 2CH 2OH + 6O 2 4CO 2 + 5H 2O or C 4H 9OH M4 A biofuel is a fuel produced from (renewable) biological (re)source(s) (renewable) (re)source(s) from (a specified) plant(s)/fruit(s)/tree(s) In M4 Ignore references to carbon neutral Ignore sugar and glucose 4 (d) M butan--ol is a primary or (alcohol) M2 Displayed formula (ONLY) for butanal CH CH 2CH 2CHO M Displayed formula (ONLY) for butanoic acid CH CH 2CH 2COOH M2 and M displayed formula must have all bonds drawn out including the O H but ignore angles. If butanal and butanoic acid formulae are both correctly given but not displayed, credit one mark out of two. M4 Oxidation (oxidised) Redox M5 orange to green Both colours required for M5 Ignore states 5 [5] Page 6
M5. (a) Allow mark each for any correctly drawn primary, secondary and tertiary alcohol of molecular formula C 4H 8O Tertiary alcohol cannot be oxidised (b) Region 500 400 cm exact match to spectrum of known compound (c) A B CH CH 2CH 2OH CH CH 2 O CH () or CH CH(OH)CH () C one alkene e.g. D one cycloalkane e.g. CH 2=CHCH 2CH 2CH CH CH=CH CH 2CH (CH ) 2C=CHCH H 2C=C(CH )CH 2CH () etc E F CH CH 2CHO () CH COCH () 6 [2] Page 7