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1 Unit 4 + 5 (2008- syllabus). Paper details 4U4 Exam 1h 40m. 3 sections. (90 mks??). Section A,B & C A = multiple choice (objective Q's) B = Short answers.

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Presentation on theme: "1 Unit 4 + 5 (2008- syllabus). Paper details 4U4 Exam 1h 40m. 3 sections. (90 mks??). Section A,B & C A = multiple choice (objective Q's) B = Short answers."— Presentation transcript:

1 1 Unit (2008- syllabus)

2 Paper details 4U4 Exam 1h 40m. 3 sections. (90 mks??). Section A,B & C A = multiple choice (objective Q's) B = Short answers & extended Q's inc. analysis and evaluation of practical work C = Data questions and use of data

3 Paper details U5 Exam 1h 40m. 90 marks. Section A,B & C A = multiple choice (objective Q's) B = Short answers & extended Q's inc. analysis and evaluation of practical work “Contemporary context questions”.C = Questions requiring extended answers. 'Senarios' may be given and students expected to answer Q's based on the chemistry presented. “Contemporary context questions”. Sections B & C will be where a students can show their full ability. Knowledge from previous units required. QWC considered. Data book can be used.

4 Unit 2.10 (Organic I) Reaction summary Followed by Unit 4.8 Further organic chemistry ( Organic II) Mike Allan Hamzah. INTEC My information here is free of all restrictions

5 Recall of function groups… Functional groups. Atoms or sequences of atoms causing deviations in electron density to that of its hydrocarbon equivalent. E.g ethanol & ethane (C=C, -X, -OH, -COOH <<< Unit 2.10) CMgBr, -COOH, COOR, CHO, CO, -NH 2, -NHR, -NR 2, -COX, CONR 2, CN, CMgBr, -COOH, COOR, CHO, CO, -NH 2, -NHR, -NR 2, -COX, CONR 2, CN, Ether: R 3 C-O-CR 3 (R=H or carbon) Unit 2.10 summary

6 Alkanes CO 2 + H 2 O As fuels Halogenoalkanes Functionalization via halogen radicals (need X 2 and U.V.) Pyrolysis (thermal cracking) not on syallabus Alkanes of different types and alkenes

7 Alkenes KMnO 4 (aq) & OH - (aq) C=C A diol C-C HOOH polymerization C-C-C poly(ethene) - PE poly(propene) – PP poly(vinylchloride) - PVC poly(tetrafluoroethene) – PTFE Hydrogenation H 2 (g) + Rayney nickel Alkenes ADDITION REACTIONS !!! cis- and trans- isomers possible due to restricted C=C bond Polymers HX Hydrogen halogenation Use Markovnikov If unsymmetrical Halogenation (X 2 ) C-C XX

8 C-X Halogenoalkanes C-NH 2 KCN Reflux under heat (ethanol solvent) Nucleophilic substitution and Elimination reactions KOH(ethanolic) Reflux under heat (dehydrohalogenation) Elimination! C=C C chain extended !!! Polysubstitution possible. To 2 0 and 3 0 amine C-C≡N KOH(aq) Reflux under heat C-OH Displaced X - This can therefore be uses to test for the (halogen)type of R-X After reflux add HNO 3 (aq) THEN Ag(NO3)(aq) Excess c.NH 3 Reflux under heat

9 C-OH Alcohols NaX and c.H 2 SO 4 Reflux under heat Halogenoalkane (alkyl halide) C-X oxidation C-O - Na + K 2 Cr 2 O 7 (aq) + H 2 SO 4 (aq) Distill for aldehyde Reflux for carbox. acid. PCl 5 / PCl 3 / SOCl 2 2P + 3Br 2 2P + 3I 2 Nucleophilic substitution, elimination, and oxidation reactions Na(s) c. H 2 SO o (elimination) C=C sodium alkoxide C Aldehydes & ketones COOH O R R’ Carbox. acids If aldehyde oxidation Al 2 O 3 (s) 300 o C and P 4 O 10 can also be used N.B. Initial alcohol must be dry

10 4.8 Further Organic

11 enantiomers

12 4.8 Further Organic Chirality a) recall the meaning of structural and E-Z isomerism (geometric/cis-trans isomerism) Z is is cis E = trans Identify largest group by atomic number (or mass) on one side of db (e.g A & B) Identify largest group by atomic number (or mass) on one side of db (e.g A & B) Do the same on other side (D and G) Do the same on other side (D and G) Atoms of greatest at# on same side of the db, then compound = Z isomer. Atoms of greatest at# on same side of the db, then compound = Z isomer.

13 4.8.1 Chirality b) demonstrate an understanding of the existence of optical isomerism resulting from chiral centre(s) in a molecule with asymmetric carbon atom(s) and understand optical isomers as object and non-superimposable mirror images Chiral = non superimposable on its mirror image. A pair of enantiomers is the result.Chiral = non superimposable on its mirror image. A pair of enantiomers is the result. Asymetric = no element of symmetry (reflection, rotation, reflection & inversion)Asymetric = no element of symmetry (reflection, rotation, reflection & inversion) Mars101/definitions.htm creview/bp/1organic/chirality.html

14 popmonoppl ]A substance is optically active if it rotates the plane of polarisation of monochromatic plane polarised light (ppl). [ pop of mono ppl ] One enantiomer will rotate light by some angle, say +x degrees, but the other enantiomer will rotate the plane of monochromatic ppl by the same magnitude but in the opposite direction, say –x degrees Chirality c) recall optical activity as the ability of a single optical isomer to rotate the plane of polarization of plane-polarized monochromatic light in molecules containing a single chiral centre and understand the nature of a racemic mixture Huh?...

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16 scientific.nl/Producten/Polarimet er/Polarisg[1].jpg y/images/polarimeter.jpg Huh?...

17 One source of chirality (the property of being chiral) is in aliphatics with 4 different gps on the same C atom… but 4 diff gps isn’t the only way u can get chiral molecules. E.g. DNA helix, spirenes…One source of chirality (the property of being chiral) is in aliphatics with 4 different gps on the same C atom… but 4 diff gps isn’t the only way u can get chiral molecules. E.g. DNA helix, spirenes…

18 Different optical isomers can have radically different BIOLOGICAL properties. Phys props (other than optical rotation) usually the same.

19 Thalidomide – enantiomers showing different biological effects

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21 4.8.1 Chirality d) use data on optical activity of reactants and products as evidence for proposed mechanisms, as in SN2 and SN1 and addition to carbonyl compounds. Transition state.SN2 (animation page) (OR video1 vid2) rxns involve inversion of centre of chiraity (stereocentre). Product is optically active – will cause plane of polarisation of monochromatic ppl to rotate. Transition state.animation pagevideo1vid2

22 S N2 “Stereochemistry at a glance By Jason Eames, Josephine Peach. Google books P42

23 4.8.1 Chirality d) use data on optical activity of reactants and products as evidence for proposed mechanisms, as in SN2 and SN1 and addition to carbonyl compounds. Carbocation intermediate (may rearrange).SN1 (animation page) rxns have the substrate give racemic mixtures (mixtures of both enantiomer products). Product mixture is optically inactive – no effect of plane of polarisation of monochromatic ppl. Carbocation intermediate (may rearrange).animation page

24 “Mechanisms in organic reactions” By Richard A. Jackson.Google books P104 S N1

25 AldehydesAldehydes RCHO R can be H or hydrocarbon. Methanal, ethanal, propoanal… benzaldehyde KetonesKetones RCOR’ R cannot be H, must be hydrocarbon (no methanone or ethanone) propanone(acetone), cyclohexanone Carbonyl compounds a) give examples of molecules that contain the aldehyde or ketone functional group Volatility Ald’s and ket’s with larger more complicated perfumes and flavourings. Volatility is important.

26 4.8.2 Carbonyl compounds b) e xplain the physical properties of aldehydes and ketones relating this to the lack of hydrogen bonding between molecules and their solubility in water in terms of hydrogen bonding with the water Methanal (polar) gas Propanone (polar) Volatile liquid Can H bond with water.!! & both polar, so soluble in water up to a few C’s long. Electron density maps Red =  -

27 Ethanal (not shown) is the first aldehyde to be liquid at RTP. Bpt > corresponding alkanes, but corresponding alkanes, but < than corresponding alcohols. arey/student/olc/graphics/carey04oc/ch17/ figures/acetoneepot2.jpg arey/student/olc/graphics/carey04oc/ch17/ figures/methanalepot.jpg

28 Aldehydes ‘n Ketones.. O C C : C O H C : C ketone aldehyde Aldehydes tend to be more reactive than ketones because, sterically, of the lack of extra alkyl chain as present in ketones. Also the alkyl chain, by inductive effect (+ I ), releases e- density to carbonyl and lowering charge on carbonyl, delocalizing the charge over the nearby area.

29 4.8.2 Carbonyl compounds Carbonyl compounds c) describe and carry out, where appropriate, the reactions of carbonyl compounds. This will be limited to: i.oxidation with Fehling’s or Benedict’s solution, Tollens’ reagent and acidified dichromate(VI) ions ii.reduction with lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether

30 Aldehydes ‘n Ketones 1 O Alcohol 2 O Alcohol 3 O Alcohol aldehyde carboxylic acid ketone LiAlH 4 in dry ether (esters can be reduced too!!!) OXIDATION Reduction AlcoholsCarbonyls Carbox. acids NaBH 4 (can be aq too!) Aldehydes Aldehydes can undergo oxid n and Red n Ketones Ketones undergo Red n Acts as if a source of H - (a nucleophile)

31 TEST to discriminate aldehydes from ketones Aldehydes can be oxidised by a number of compounds, some are employed as a TEST to discriminate aldehydes from ketones 1)Fehlings solution (Cu 2+ complex) 2)Tollens reagent / test (ammoniacal silver nitrate – [Ag(NH 3 ) 2 ] + complex 3)Acidified K 2 Cr 2 O 7 (aq) or acidified KMnO 4 (aq) OXIDATION Aldehydes ‘n Ketones

32 Fehlings A is a solution of CuSO 4 (aq) Fehlings B sodium tartrate solution and NaOH Both solutions mixed together to form the chelated Cu 2+ after intitial Cu(OH) 2 ppte seen by the bidentate tartrate ions surrounding the Cu 2+ - deprotonation of hexaaqua ligand does not occur – tartrate is a stronger ligand. Cu 2+ only reacts in one way and that is to gain electrons! It causes the loss of e- from a different species  is an O.A. Aldehydes ‘n Ketones On heating (to inc. rate of rxn), a red Cu(I) oxide precipitate forms 1) Fehlings sol n

33 AgNO 3 (aq) + few drops of NaOH(aq)  Ag(OH)(s) Add NH 3 (aq) until black ppte just dissolves. [Ag(NH 3 ) 2 ] + forms {counter ion = - OH} Aldehydes ‘n Ketones 2) Tollens reagent Heat with aldehyde and Ag(s) is deposited on walls of glass container. A silver mirror is formed. If solution or container is dirty grey / black Ag 2 O(s) ppte can form.

34 INTERVAL

35 cyanide anionshalogenoalkanesIn rxn with of cyanide anions with halogenoalkanes, (nucleophilic substitution), X substitutes (leaves) with :C≡N, so simply use KCN in a mix of ethanol and water solvent and refluxing under heat. nucleophilic additionHowever in the addition reactions with carbonyls, nucleophilic addition takes place. HCN(a gas) adds rapdily to carbonyls, e.g ethanal + HCN(g)  2-hydroxypropanenitrile. CH 3 CH(OH)-CN HCN made by adding dil H2SO4 with KCN(in excess to allow sufficient –’ve CN ions Carbonyl compounds Carbonyl compounds c) describe and carry out, where appropriate, the reactions of carbonyl compounds. This will be limited to: iii.nucleophilic addition of HCN in the presence of KCN, using curly arrows, relevant lone pairs, dipoles and evidence of optical activity to show the mechanism Aldehydes ‘n Ketones HCN H : CN ⇁ ↼

36 Alkaline conditions don’t allow for the protonation of the carbonyl gp but do give high (:CN) - concentration. A compromise of about pH 5 gives the best results. Animation page.Animation page Aldehydes ‘n Ketones O H C H3CH3C :CN - O: H C H3CH3C CN - H+H+ OH H C H3CH3C CN A CYANOHYDRIN (an  -hydroxy nitrile) is produced. These compounds are useful for (further) synthesis. Q: State a property of cyanohydrins…

37 Alkaline conditions don’t allow for the protonation of the carbonyl gp but do give high (:CN) - concentration. A compromise of about pH 5 gives the best results. Animation pageAnimation page Aldehydes ‘n Ketones O H C H3CH3C :CN - O: H C H3CH3C CN - H+H+ OH H C H3CH3C CN A CYANOHYDRIN (an  -hydroxy nitrile) is produced. These compounds are useful for (further) synthesis. (or H-CN) (Generates H+) * Q: State a property of cyanohydrins…

38 Aldehydes ‘n Ketones Nitriles (CYANOHYDRINs) can undergo hydrolysis reactions OH H C H3CH3C CN OH H C H3CH3C O C Dilute acid (H 2 SO 4 ) Heat under reflux An  hydroxyacid Dilute NaOH can also be used. Heat under reflux but like base hydrolysis of esters, the anion of the carboxylic acid will form!!!

39 Each hydrazine reacts with carbonyls to form a hydrazone. Hydrazine itself is very toxic and so is no longer used. The dinitrophenyl version is employed instead. Aldehydes ‘n Ketones TEST Specific for carbonyl…!!! The 2,4-dnp test This lone pair is the active one and attacks the carbonyl carbon

40 H Aldehydes ‘n Ketones TEST The 2,4-dnp test O H C H3CH3C (1) (2) lp on N acts as a nucleophile.. O H C : H3CH3C : - N & O undergo proton exchange.. O H C : H3CH3C ck A hydrazone ck orange  Yellow ppte (3) (4) (5) (6) (7) ++++

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43 48 propanal acetone methylpropanal 187(183) 75 butanal butanone methylbutanal methylbutanal pentanone pentanone pentanal 107(98) methyl-2-pentanone hexen-2-one methyl-3-penten-2-one cyclopentanone hexanal 104(107) heptanone methyl-2-hexanone 95 Bp of Starting Carbonyl Unknown mp of 2,4-DNP Derivative 131 hexanal 104(107) heptanone methyl-2-hexanone heptanone heptanone heptanal cyclohexanone methylcyclohexanone octanone benzaldehyde (PhCHO) o-methylbenzaldehyde p-methylbenzaldehyde ethanoylbenzene phenyl-2-propanone (2-methylpropanoyl)benzene propanoylbenzene p-methylacetophenone butanoylbenzene phenyl-2-butanone p-methoxybenzaldehyde 253 mp of 2,4-DNP Derivative Bp of Starting Carbonyl Unknown

44 Some aldehydes, some ketones and some alcohols… Specific reaction… Triiodomethane rxn (iodoform precipitation reaction) DOES NOT: a) Identify carbonyls from alcohols b) Identify aldehydes from ketones  

45 Triiodomethane rxn (iodoform precipitation reaction) So what does it do? methyl carbonyls a) Tests for methyl carbonyls b) Tests for methyl alcohols which can be oxidised to methyl carbonyls. Note: cannot be tertiary alcohols in that case!

46 Triiodomethane rxn (iodoform precipitation reaction) Required reagents: I 2 (aq) + NaOH(aq) or KI(aq) + NaClO(aq) (ClO - is an O.A. and ‘dynamically converts I - into I 2 ) All these alpha H’s get replaced by I

47 Triiodomethane rxn (iodoform precipitation reaction) Forms rapidly Triiodomethane (ioodoform), an unpolar SOLID, ends up breaking away. (appropriate alcohol versions get oxidised to this acyl gp first) Carboxylate anion on other fragment dissolves in soln

48 Triiodomethane rxn (iodoform precipitation reaction) The triiodomethane smells like antiseptic or a dry cleaners (dry cleaners used to use trichloromethane – a compound (probably toxic: carconogenic, tetragenic and mutagenic – not that nice really and it’s said to destroy ozone.) Always better to ID iodoform from the ppte rather than the smell !!! Test may be problematical – my guess [I 2 ] is too low in the ‘bench’ test solution.

49 Further Organic revision. Source: Problem 1. Compound A, C 3 H 8 0, gives steamy fumes when reacted with phosphorus pentachloride. On oxidation with acidified potassium dichromate solution A gives B, C 3 H 6 0. This, with a source of H 3 C: - nucleophile, gives C upon addition of acid, C 4 H 10 O. C does not react with acidified potassium dichromate solution. Treatment of C with excess hot concentrated sulphuric acid gives D, C 4 H 8, which on reaction with hydrogen bromide gives mainly 2-bromo-2-methylpropane. Find the structures of A to D, giving reasons and equations for the reactions which occur.

50 Further Organic revision. Source: Problem 2. Benzene C 6 H 6 and chloromethane CH 3 Cl react in the presence of aluminium chloride to give A, C 7 H 8. A reacts with chlorine in sunlight to give B, C 7 H 7 Cl, which reacts with aqueous sodium hydroxide to give C, C 7 H 8 O. Mild oxidation of C gives D, C 7 H 6 O, which with 2,4- dinitrophenylhydrazine gives an orange precipitate. Further oxidation of D gives E, C 7 H 6 O 2, which can also be produced from A by vigorous oxidation with alkaline potassium manganate(VII) solution. The reaction of B with potassium cyanide under suitable conditions gives F, C 8 H 7 N, which in turn can be reduced to G, C 8 H 11 N. Identify the substances A to G, giving reasons for your choice and writing equations for the reactions that occur. Write the mechanism for the reaction between benzene and chloromethane. Suggest another series of reactions by means of which you could convert F to G.

51 Carboxylic acids a.give some examples of molecules that contain the carboxylic acid functional group b.explain the physical properties of carboxylic acids in relation to their boiling temperatures and solubility due to hydrogen bonding

52 Palmitic acid C16 H32 O2 benzoic acid C16 H32 O2

53 R-COOH & bpt formic acid, boils at 101 °C Carboxylic acids have much higher boiling points than hydrocarbons, alcohols, ethers, aldehydes, or ketones of similar molecular weight. Even the simplest carboxylic acid, formic acid, boils at 101 °C which is considerably higher than the boiling point of ethanol (ethyl alcohol), C2H5OH, which boils at 78.5 °C, although the two have nearly identical molecular weights. The difference is that two molecules of a carboxylic acid form two hydrogen bonds with each other (two alcohol molecules can only form one). Thus, carboxylic acids exist as dimers (pairs of molecules), not only in the liquid state but even to some extent in the gaseous state. Therefore, boiling a carboxylic acid requires the addition of more heat than boiling the corresponding alcohol, because (1) if the dimer persists in the gaseous state, the molecular weight is in effect doubled; and, (2) if the dimer is broken upon boiling, extra energy is required to break the two hydrogen bonds. Carboxylic acids with higher molecular weights are solids at room temperature (e.g., benzoic and palmitic acids). Virtually all salts of carboxylic acids are solids at room temperature, as can be expected for ionic compounds.

54 NameFormulaMelting Point ( o C)Boiling Point ( o C) formicHCOOH aceticCH3COOH propionicCH3CH2COOH butyricCH3(CH2)2COOH-6164 valericCH3(CH2)3COOH caproicCH3(CH2)4COOH-3205 lauricCH3(CH2)10COOH44225 myristicCH3(CH2)12COOH54251 palmiticCH3(CH2)14COOH63269 stearicCH3(CH2)16COOH70287 oleiccis-9-Octadecenoic16223 cyclohexanecarboxyliccyclo-C6H11COOH31233 phenylaceticC6H5CH2COOH77266 benzoicC6H5COOH o-toluico-CH3C6H4COOH m-toluicm-CH3C6H4COOH p-toluicp-CH3C6H4COOH

55 A look at the COOH functional group O O C H Because both functional groups are on the same carbon, each group strongly affects the properties of the other group, therefore each part produces: a unique whole. So do NOT consider the COOH group as showing properties of alcohol or of carbonyls. carbonyl alcohol At first sight…

56 c.describe the preparation of carboxylic acids to include oxidation of alcohols and carbonyl compounds and the hydrolysis of nitriles d.describe and carry out, where appropriate, the reactions of carboxylic acids. This will be limited to: i.reduction with lithium tetrahydridoaluminate (lithium aluminium hydride) in dry ether (ethoxyethane) ii.neutralization to produce salts, eg to determine the amount of citric acid in fruit iii.phosphorus(V) chloride (phosphorus pentachloride) iv.reactions with alcohols in the presence of an acid catalyst, eg the preparation of ethyl ethanoate as a solvent or as pineapple flavouring.

57 K 2 Cr 2 O 7 (aq) + HCl (aq) Unit Carboxylic acids 1 o alcohols O O C H aldehydes K 2 Cr 2 O 7 (aq) + HCl (aq) Grignards 1)CO 2 2)HCl (aq) Acid halides H 2 O (l) Esters ( Inc. polyesters ) Hydrolysis of amides and acidic workup PCl 5 Acid halides

58 1 O Alcohol 2 O Alcohol 3 O Alcohol aldehyde carboxylic acid ketone LiAlH 4 in dry ether (esters can be reduced too!!!) OXIDATION Reduction AlcoholsCarbonyls Carbox. acids NaBH 4 (can be aq too!) Memory aid. Alcohols and related compounds

59 Carbox. acids

60 Nitriles

61 Acid chlorides

62 Fatty acids

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67 Margarine

68 Margarine (?) Unsaturated oil + H2(g) -> saturated fat Add vitamins, colour…

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70 Soap: Where you get fatty acids, you can get esters! Esters Production of Biodiesel (esters) and base hydrolysis of esters to Make Soap Make Soap

71 Transesterification - Boidiesel

72 Transesterification

73 Biodiesel.Transesterification

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