itrogen ompounds - MS. (a) (i) is an amine and a carboxylic acid / contains both and functional groups () AW (c) R( ) () R Does not fit the formula because and are not attached to the same carbon () AW 3 displayed amide bond () rest of the structure also correct () (allow full marks for a correct anhydride structure) [7]. (i) one amide link shown correctly () glycine and phenylalanine parts shown correctly () proline linked correctly () 3 6 () 3. (i) water / evidence of a solution in water eg (aq), dil, 6M or conc for l () T conc 3 or conc S 4 a named strong acid or alkali (heated under) reflux /() amino acids () (iii) correct structure for one of the amino acids () correct ionic form for reagent used in a(i) eg + - / () (iv) reaction with water to split/break down the compound () peptide bond in the compound is broken / diagram to show AW () [4] [7] 4. General formula of an α-amino acid R () Diagram to show length of polypeptide / repeat unit eg R R R3 with: displayed peptide bond ()
5. (i) correct structure with a minimum of two amino acids joined (can be scored by a dipeptide) () idea of polymerisation shown by end bonds () loss of water () relate variety to different R groups / sequence of amino acids () AW 6 Quality of written communication: correct organisation and use of both of the terms: condensation polymer(isation) and peptide bond/link () [7] R must attempt 3D ALLW R( ) any order for R, and but must be next to must be shown ALLW brackets around are not essential ALLW structure use RE symbol in the tools to denote whether or not each chiral is a reflection of the one given in the question RE RE RE 3 3 3 3 3 3 both chiral s are mirror images RE top chiral only is a mirror image bottom chiral only is a mirror image each chiral must have bonds, wedge bond (IGRE shading) & dash bond (IGRE wedge) check the clockwise orientation of each. For each start with the and if on the: top the is followed by it is not a mirror image. If it is a mirror image annotate using RE. bottom the is followed by 3 it is not a mirror image. If it is a mirror image annotate using RE. the four groups can be attached in any order. If the molecule is drawn upside down clockwise becomes anti-clockwise. MUST check that the drawn structure is non-superimposable irrespective of the orientation or the way it has been drawn. IGRE bond linkage for all groups 3 [4]
6. (a) (i) R / R allow R and in any order they both have the () group / or in words () T just they both have and (b) + 3 R group is in glycine and in glutamic acid () 3 + () - and side chain unaffected () one () - - both () - and rest of molecule () (c) glutamic acid/molecule with optical isomers is chiral () has four different / distinguishable groups attached to a carbon () T just different atoms the mirror images/isomers cannot be superimposed AW () one diagram showing two 3-D bonds not opposite each other, and not with angles looking like 90 () 5 3-D diagram of the other isomer (allow ecf on one 3-D error) () all groups correctly connected for glutamic acid in both diagrams () glycine only has three different groups / two groups are the same / 3-D diagram used to show symmetry () 8 quality of written communication for correct use and organisation of at least one technical term: *(in the correct place), non-superimposable, enantiomer, stereoisomer(ism), tetrahedral, assymetric () [6] 7. and at least one correct skeletal formula () correct cis and trans isomers of but--enal () []
9. ( ) 6 ( ) 8 ALLW ALLW ALLW for ALLW acid chloride, l( ) 8 l ALLW displayed formulae or skeletal formulae [] 0. (i) l l or () () any valid suggestion to explain or describe stronger intermolecular forces e.g. omex is planar so packs together more easily / greater -bonding / London forces between molecules () AW (ignore arguments based on Mr) [3]. (i) addition (polymerisation) () T additional (iii) π-bond breaks () () many molecules join / a long chain forms / equation to show this using n () [4]
. (a) ( ) ( ) e 4 () ( ) ( ) 4 6 monomers connected by () correct repeat shown () condensation addition () for both (b) l + + (c) 3 ( ) 6 3 ( ) 4 () allow mark for: both 3 + ( ) 6 + 3 and ( ) 4 4 (d) (i) 4 (iii) R where R=, 3, or 6 5 () any three different chemically or biologically correct differences between amino acids and the nylon monomers ()()() - eg protein monomers are amino acids / nylon monomers are a (di)amine/base and a (di)acid protein monomers have different types/r groups / nylon monomers are two types/no variation protein monomers have stereo/optical isomers/are chiral protein monomers have higher melting points/ form zwitterions other possible answers include: nylon monomers have longer chain length/no other functional groups / no aromatic content / are symmetrical etc 3 don t allow comparisons solubility or M r []
3. (i) equation ( 3 ) + reactants 3 + 3 ALLW products ( 3 ) + 6 4 3 6 4 + 3 ALLW 0 3 is D T ALLW molecular formulae 3 3 R 3 3 ALLW amide shown as either 3 R 3 R 3 R 3 ALLW ester shown as either 3 R 3
(iii) to ensure that there are no (harmful) side effects ALLW impurities reduce effectiveness (of drug) R might be toxic R avoids litigation R harmful R hazardous ALLW to ensure that the drug/active component is safe IGRE dangerous R nasty R can kill R increased dosage [4] 4. (i) 3 0 3 () ketone () ester () alkene () 3 (iii) op t i c a l * E / Z * * op t i c a l both optical () E/Z () (iv) possible side effects of other chiral compound () increased costs/difficulty of separating of isomers () using bacteria within synthetic route () max [8] 5. (a) (i) ab 4 () 4-hydroxypentanoic acid () (b) (i) section of the polymer () e.g. 3 3 3 a correct repeat shown () e.g. 3 allow ecf from (i) only if the repeat is every carbons along the chain and has a
(c) (i) 7 3 () 7 3 + 8½ 7 + 6 or ecf from (i)) formulae () balancing () (iii) idea of providing oxygen / reducing incomplete combustion AW () (d) (i) heat/warm/reflux () a / K(aq) () G is an ester / sensible argument based on polarity () [] 6. (i) a carbon with four different groups attached () a chiral carbon /centre () different spatial / 3-D arrangement (of the groups) () (stereo)isomers / mirror images are non-superimposable / molecules are asymmetric () 3 AY 3 out of 4 marks contains chiral centres () each can have (stereo)isomers/ possibilities AW () (iv) higher doses are required () the drug /other stereoisomers may have (harmful) side-effects () [8]