Ch 3 c c ch 3 c ch 3 ch 2 oh c c oh allowed allowed

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CH3CCCH3CCH3CH2OHCCOHallowedallowednot allowednot allowednot allowedNH2CCNH2NH2NH2NO2allowedallowedallowedallowednot allowedCNCCCNCOOHCCCOOHCCOOHnot allowednot allowednot allowednot allowednot allowedCHOCCCHOCCHOCOClCCCOClnot allowednot allowednot allowednot allowednot allowedRepresentation of CH2byCH2will be penalisedSome examples are given here ofstructuresfor specific compounds that shouldnotgain credit (but, exceptionsmaybe made in the context of balancing equations)CH3COHforethanalCH3CH2HOforethanolOHCH2CH3forethanolC2H6OforethanolCH2CH2foretheneCH2.CH2foretheneCH2:CH2foretheneEach of the followingshould gain creditas alternatives to correct representations ofthe structures.CH2= CH2forethene,H2C=CH2CH3CHOHCH3forpropan-2-ol,CH3CH(OH)CH3
MARK SCHEMEA-LEVEL CHEMISTRY7405/1JUNE 20208In most cases, the use of ‘sticks’to represent C ─ H bonds in a structure shouldnotbepenalised.The exceptions to this when “sticks” will be penalised includestructures in mechanisms wherethe C ─ H bond is essential (egeliminationreactions in halogenoalkanes and alcohols)when a displayed formula is requiredwhen a skeletal structure is required or has been drawn by the candidate.3.13Organic namesAs a general principle, non-IUPAC names or incorrect spelling or incomplete namesshouldnotgain credit.Some illustrations are given here.Unnecessary but not wrong numbers willnotbe penalised such as the number ‘2’ in2-methylpropane or the number ‘1’ in 2-chlorobutan-1-oic acid.but-2-olshould bebutan-2-ol2-hydroxybutaneshould bebutan-2-olbutane-2-olshould bebutan-2-ol2-butanolshould bebutan-2-olethan-1,2-diolshould beethane-1,2-diol2-methpropan-2-olshould be2-methylpropan-2-ol2-methylbutan-3-olshould be3-methylbutan-2-ol3-methylpentanshould be3-methylpentane3-mythylpentaneshould be3-methylpentane3-methypentaneshould be3-methylpentanepropanitrileshould bepropanenitrileaminethaneshould beethylamine(although aminoethane can gain credit)2-methyl-3-bromobutaneshould be2-bromo-3-methylbutane3-bromo-2-methylbutaneshould be2-bromo-3-methylbutane3-methyl-2-bromobutaneshould be2-bromo-3-methylbutane2-methylbut-3-eneshould be3-methylbut-1-enedifluorodichloromethaneshould bedichlorodifluoromethane
MARK SCHEMEA-LEVEL CHEMISTRY7405/1JUNE 202093.14Organic reaction mechanismsCurly arrows should originate either from a lone pair of electrons or from a bond.The following representationsshould not gain creditand will be penalised each timewithin a clip.CH3BrCH3BrCH3Br....OHOH..__:For example, the following would score zero marksH3CCHHBrHOWhen the curly arrow is showing the formation of a bond to an atom, the arrow can godirectly to the relevant atom, alongside the relevant atom ormore than half-waytowardsthe relevant atom.

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Chemistry, Atom, Ion, MARK SCHEME, M2 Browning machine gun

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