Unit 4.5

Unit 4.5 Organic chemistry II Recognise structural isomers, stereoisomerism as geometrical (cis-trans) or opticalExplain the existence of geometrical (cis-trans) isomerism resulting from restricted rotation about a carbon-carbon double bondUnderstand the existence of optical isomerism resulting from a chiral centre in molecules with a single asymmetric carbon atom,Understand optical isomers as object and non-superimposable mirror imagesRecall optical activity as the ability of a single optical isomer to rotate the plane of polarisation of plane polarised monochromatic light and understand the nature of a racemic mixture

Isomer Same molecular formula, different structural formulae

Structural isomerism Occurs when 2 or more different structural formulae can be written for the same molecular formulaChain isomers Different arrangements of carbon skeleton Similar chemical properties, differ in physical properties(Mt)because of change in shape of molecule

Positional isomers Same skeleton and functional group, side chains/functional groups are in different positions on the carbon chain Differ in physical properties

Functional group isomers Same atoms arranged into different functional groups Differ in physical & chemical properties

2 bonds in the C=C double bond are not the same, bond energy of C=C (612kJmol –1) is greater than C-C (348kJmol –1) but not as twice as big hence pi bond is weaker than the sigma bondStereoisomerism Molecules have same molecular formula, same structural formula, but atoms have a different 3d arrangement(orientation in space). Differ in physical properties

Stereoisomerism found in any molecule of the type:

Geometric Isomerism Occurs when there’s restricted rotation about a bond(C=C double bond where each of the two C atoms carries 2 different atoms/groups)differ in physical properties(different positions of groups, chains affects shape, dipoles, intermolecular forces)Single sigma bond Free rotation about this bond without any reduction in degree of overlapDouble bond Restricted rotation about C=C double bond because rotation would lead to a decrease in overlap of p orbitals that give the pi bond

Optical Isomerism Where molecules(chiral molecules) have mirror-image isomers that are not superimposable on the original compound. Sole criterion for chirality is existence of non-superimposable mirror images• Commonest origin of chirality is a carbon atom having 4 diff groups attached to it(the chiral centre)• Molecules will not be chiral if one chiral centre is the mirror image of the other in a 2 chiral centred molecule• Possible to have chirality in molecules that don’t have chiral centres(molecule is helical)

Chiral molecules rotate plane of polarisation if plane-polarised monochromatic light is shone through them(sodium light) must be monochromatic because angle of rotation depends on wavelength of light used. In some wavelengths it’s 0Dextrorotatory (+) in front of the name, molecules that rotate the plane to the right(clockwise looking into the sample)Laevorotatory (-) in front of the name, molecules rotating the plane to the leftRacemic Mixture No rotation, solution contains equal(molar) amounts of each 2

forms of chiral molecule. Clockwise rotation of one isomer cancelled by anticlockwise rotation from the other

Chiral Has 2 isomers that are non superimposable mirror imagesChiral molecule A molecule that is non-superimposable on its mirror image

QuestionsHow is optical activity detected experimentally? Rotation of plane polarised light

bond polarityElectronegativity(EN) Strength(of an atom)to attract(the pair of)electrons in a covalent bond - EN affects bond length with larger differences giving shorter bonds- More electronegative atoms attract shared electrons more towards, itself and acquire a partial negative charge• Electronegativity decreases going down a group(most electronegative element is fluorine)• Electronegativity increases across period 3, elements on the LHS lose electrons and elements on the RHS gain electrons to achieve a stable structure* Ionic bonds are partially covalent when EN is small * Covalent bonds are partially ionic(creation of dipoles)when EN is largePolarisability The ease with which the electron cloud of an anion is distorted by a cation so there’s electron sharing• Smaller and higher the charge(higher the charge density)on the cation, the more polarising it is• Larger and higher the charge on the anion, the more easily it is polarized

Features favouring ionic bonding:• Large cation metal, of low charge, having a low IE• Large anion non metal, of low charge, having a high EA

- Large anions most stable with large cations Small cations most stable with small anions- A covalent bond is polar if electrons in the bond are unequally shared

formation of polyesters and polyamides

Condensation polymers

esters with acids and alkalis in aqueous solutioncarbonyl compounds with hydrogen cyanide, 2,4-dinitrophenylhydrazine, alkaline ammoniacal silver nitrate solution, Fehling’s solution, ethanoyl chloride with water, alcohols, ammonia and primary aminesprimary amines with aqueous hydrogen ions, acid chlorides nitriles undergoing hydrolysis and undergoing reductionamides with phosphorus(V) oxide and bromine in aqueous alkaliamino acids with acids and bases, their zwitterion structures.iodine in the presence of alkali (or potassium iodide and sodium chlorate(I)), (sodium borohydride) sodium tetrahydridoborate(III) (lithium aluminium hydride) lithium tetrahydridoaluminate(III) Halogeno-compounds with magnesium to form Grignard reagents. Grignard reagents reactions with water, carbon dioxide and carbonyl compounds.

Recall that Grignard reagents act as nucleophilesCarboxylic acids with alcohols, (lithium aluminium hydride), phosphorus pentachloride, sodium carbonate and sodium hydrogencarbonaterules for nomenclature

Functional group An atom/group of atoms in an organic compound that determines all the possible chemical reactions for that compound

Compound type Functional group Compound type Functional groupHalogenoalkanesGrignard reagentAldehydesKetones

R-X (X is Cl, Br, I)R-MgX (X is a halogen atom)R1-CHO R1 can be a H atomR1-CO-R2

R1 & R2 must contain at least one C atom

Acid chloridesAminesAmidesNitrilesAmino acids

R-COClR-NH2

R-CONH2

R-CNRCH(NH3

+)COO-

Names based on longest continuous C chainMeth = 1 Eth = 2 Prop = 3 But = 4 Pent = 5 Hex = 6Hept = 7Oct = 8

Carbonyl(C=O) compoundsaldehydes & ketones

Alkyl groupsA methyl group is CH3

An ethyl group is CH3CH2

2-methylpentane 2,3-dimethylbutane

2,2-dimethylbutane 1,1,1-trichloroethane

pentan-3-one

ethylamine

Propanamide

Dimethylamine Trimethylamine

2-aminopropane

Ethanenitrile

2-hydroxypropanenitrile

ethanoyl chloride(acid chloride)

primary (1°), secondary (2°) and tertiary (3°) alcohols is based upon the number of carbon atoms the C-OH group's carbon is bonded to.Ene – means C=C bondAlkyl group names come before name of longest C chain preceded, by a number to indicate C atom at which substitution occurredAlkyl group number comes from shortest C chain

3-ethyl-2-methylhexane 3-methylhex-2-ene

2-bromo-2-methylpropane 1-iodo-3-methylpent-2-ene

2-methylpropan-1-ol ethane-1,2-diol

HCHO methanol CH3COCH3 butanoneCH3CHO ethanol2-methylpentanal(aldehyde) propanone(ketone)

2-hydroxypropanoic acid(carboxylic acid)The hydroxy part of the name shows the presence of an -OH group. Normally, you would show that by the ending ol, but this time you can't because you've already got another ending.

esters

Alanine (2-aminopropanoic acid)An amino acid contains both an amino group, -NH2, and a carboxylic acid group, -COOH Glycine(amino acid) where R=R1=H

Grignard reagent

recognise oxidation, reduction, condensation, nucleophilic substitution or nucleophilic additionRedox (reduction oxidation reaction) describes / all chemical reactions in which atoms have their oxidation number/state changedOxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionicOxidation describes the loss of electrons by a molecule, atom or ion (From +2 to +4)Reduction describes the gain of electrons by a molecule, atom or ion (From +4 to +2)Elimination reaction Elements of a simple molecule(H2O)are removed from the organic molecule and not replaced by any other atom/group of atomsAddition reaction 2 molecules react together forming a single productElectrophilic addition Addition reaction where, electrophile attacks a molecule at a region of high electron density Substitution reaction(atom/group of atoms in a molecule replaced by another atom/group of atoms)Nucleophilic substitution δ+ C atom can be attacked by a nucleophileOH–, CN–, NH3 nucleophiles which react with haloalkanes :OH– provides a pair of electrons for C C–Br bond breaks heterolytically, both electrons from the bond taken by Br– then OH– bonds to CNucleophile (literally nucleus lover as in nucleus and phile) is a reagent that forms a chemical bond to its reaction partner (the electrophile) by donating both bonding electronsElectrophile (literally electron-lover) is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophileCondensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride, methanol, or acetic acid.

Compound Reagent Product Reaction typeAlkane Halogen Haloalkane SubstitutionAlkene Acidic(purple)KMnO4 Alcohol (colourless) Reduction

Alkaline(purple)KMnO4 Alcohol (green)HBr haloalkane Electrophilic additionH2SO4 Alcohol Electrophilic additionBromine water Decolourised from orange to

colourlessDihaloalkane

Addition

Haloalkane NaOH(aq) or KOH(aq) Alcohol Nucleophilic substitution

NaOH(ethanol) or KOH(ethanol) Alkene EliminationKCN(ethanol) Nitrile Nucleophilic

substitutionDilute nitric acid, then silver nitrate ppt of silver halide,

white- chloride, yellow – iodideAlcohol Combustion Carbon dioxide and water

PCl5 RCl + POCl3 + HClMisty fumes of HCl which turn blue litmus red

HX HaloalkanePrimary alcohol Acidified potassium dichromate

(orange)(green) aldehyde that will react with Tollens reagent to give a silver mirror

Secondary alcohol (green) ketone will not react with Tollens reagent

Tertiary alcohol (orange) no reaction

Grignard reagent• Metal carbon bond has ionic character because electronegativities(ability to attract electrons) of metals are less than that of carbon

Ether must be perfectly dry since water destroys resulting Grignard reagentdry ether, heat(reflux)

C2H5I + Mg C2H5MgIHalogenalkane ethyl magnesium iodide(Grignard reagent)

Compound Reagent Product Reaction typeGrignard reagentRMgX

Water Alkane RH Nucleophilic substitutionCarbon dioxide Carboxylic acid RCOOHMethanal HCHO Primary alcohol RCH2OHAldehydes R1CHO Secondary alcohol

RCH(OH)R1

Ketones R1COR2 Tertiary alcohol RR1R2COHCarboxylic acids RCOOH Alcohol R1OH Ester RCOOR1 Nucleophilic substitution

followed by eliminationLiAlH4 Alcohol RCH2OH ReductionPCl5 Acid chloride RCOCl Nucleophilic substitutionNa2CO3 and NaHCO3 Sodium salt RCOO-Na+

CO2 gas(gives white ppt with limewater)

Acid-base

Esters RCOOR1 Aqueous mineral acid eg HCl(aq) Alcohol R1OH and acid RCOOH

Hydrolysis (equil)

NaOH(aq) Alcohol R1OH and salt RCOO-Na+

Hydrolysis (equil)

Aldehydes RCHO or ketones RCOR1

Hydrogen cyanide(HCN(covalent)) and potassium cyanide

Cyanohydrin RCH(OH)CN or RR1C(OH)CN

Nucleophilic substitution

2, 4-dinitrophenylhydrazineTest for carbonyl(C=O) group

2, 4-dinitrophenylhydrazine(Orange ppt)

Nucleophilic substitution followed by elimination

Sodium borohydride NaBH4 or lithium aluminium hydride LiAlH4

Primary alcohol RCH2OH or secondary alcohol RCH(OH)R1

Reduction

Aldehydes RCHO (not ketones)Test for CHO group

Ammonical silver nitrate solution (Tollens reagent)

Silver mirror Reduction of the silver ion

Fehling’s solution/Benedicts solution(Blue)

Copper(I) oxide ppt (Red) Reduction of the copper(II) ion

potassium dichromate(VI)(orange)

(green)

Aldehydes RCHO acidic conditions Carboxylic acid RCOOH Oxidationalkaline conditions salt RCOO-X

ketone, 2° alcohol NaOH + I2 RCOONa + CHI3 (iodoform/yellow ppt)

Haloform

Acid chlorides ROCl Water Acid RCOOH Nucleophilic substitutionAmmonia Amide RCONH2

Alcohol R1OH Ester RCOOR1

Amine R1NH2 N- substituted amide R1CONHR

Amines RNH2 Aqueous acid eg HCl(aq) RNH3+Cl- Acid-base

Acid chloride R1OCl N-substituted amide R1CONHR

Nucleophilic substitution

Amides RCONH2 Phosphorus(V) oxide P4O10 Nitrile RCN DehydrationBromine followed by NaOH(aq) Amine RNH2 Substitution followed by

rearrangement and elimination

Nitriles RCN Aqueous acid eg HCl(aq) Acid RCOOH HydrolysisNaOH(aq) Salt RCOO-Na+

lithium aluminium hydride LiAlH4

Amine RCH2NH2 Reduction

Amino acids RCH(NH3

+)COO-Aqueous acid eg HCl(aq) Salt RCH(NH3

+)COOH Acid-baseNaOH(aq) Salt RCH(NH2)COO- Na+

QuestionsState the reagents and conditions necessary to convert CH3CH2CH(CONH2)CH3 to 2-aminobutane

• heat • with bromine • and sodium hydroxide

C H C H C H B rC H G rig na rd A B

P C L

C H C H C C H C

C O N H

H

2

2

3

3 32

2

5

3

D

M gi) C Oii) H C l(a q )

A CH3CH2CH(MgBr)CH3 B CH3CH2CH(COOH)CH3 C CH3CH2CH(COCl)CH3Reagents and conditions for CD • ammonia • and room temperatureButanone can be made from 2-bromobutane by a synthetic route involving two steps, the first using aqueous sodium hydroxide and the second potassium dichromate(VI) solution acidified with dilute sulphuric acid.(i) Give the structural formula of the intermediate compound in this synthetic route.

C H C H C HC H

O H

3 2 3

(ii) Butanone reacts with 2,4-dinitrophenylhydrazine solution but not with Fehling’s solution. Why is this?• contains C=O so reacts with 2,4 dnp • but cannot be oxidised so no reaction with Fehlings’ solution

(iii) Butanone also reacts with iodine in sodium hydroxide solution. What structural feature of butanone is shown by this reaction?

(1 )

C C HC H C H C H

O O H

3 3if in c lu d e d th en

zero

(iv) Give the structural formulae of both the organic products from the reaction in (iii).CHI3 and CH3CH2COONa

(a) Write the structural formulae of the organic products obtained when ethanoyl chloride reacts with the following compounds. Give the names of these products.(i) Ammonia, NH3 (ii) Methanol, CH3OH.

CH3CONH2 CH3COOCH3

(b) Bromoethane reacts with magnesium to form the Grignard reagent CH3CH2MgBr.This Grignard reagent reacts with: CO2, followed by hydrochloric acid, to form compound A;

water to form compound B; methanal, followed by hydrochloric acid, to form compound C.

Compounds A and C react together, in the presence of a suitable catalyst, to form compound D.(i) Write the structural formulae of compounds A, B, and C.

A = CH3CH2COOH or C2H5COOH B = CH3CH3 C = CH3CH2CH2OH or C2H5CH2OH

(ii) Draw the full structural formula of compound D

H HO HH H

C CC CC CO HH

H H HH H

(iii) Give the names of compounds C and DC = propan-1-ol D = propyl propanoate

(iv) Identify a catalyst for the reaction between compounds A and C

sulphuric acid / phosphoric acid / hydrochloric acid(a) Write equations to show the reactions of the amino acid alanine, CH3CH(NH2)COOH, with:(i) HCl CH3CH(NH2)COOH + HCl CH3CH(NH3

+Cl)COOH (ii) NaOH CH3CH(NH2)COOH + NaOH CH3CH(NH2)COONa+ + H2O

(b) Explain why alanine has a relatively high melting temperature (290 °C) Exists as zwitterion Strong attraction between oppositely charged ions

(c) Explain why alanine exists as two optical isomersDraw diagrams to show the structures of the two optical isomers.

C C

N H N H

H HC H C H3 3

2 2

C O O H C O O H

(ii) Explain how separate pure samples of each optical isomer can be distinguished from each other. Rotates the plane of (plane) polarised (monochromatic) light in opposite directions measure rotation (of plane of polarised light) in opposite directions

(d) A mixture of isomeric alkenes is obtained when butan-2-ol is dehydrated.(i) Draw diagrams to show the two structural isomers obtained when butan-2-ol is dehydrated.

H H H H

C C C CH H

H H

H H H H

C C C CH H

H Hbut-1-ene but-2-ene

(ii) One of the above structural isomers can itself exist as two different stereoisomers. Draw diagrams to clearly illustrate these two stereoisomers, and name this type of stereoisomerism.

C H H

H C H

H C

H

H CC CC C

3

H

3 3

3

geometric cis- but-2-ene trans-but-2-ene

H J K + C O

C H

C H

3

3

33

3

2

2

2

33

3

p ro p an o n eR eag en t 1

R eagen t 3

R eagen t 2C H O H

C H C O O H

C H C l

C H C O

C H C l

C H C O

CC

C

C l

N H

B r

N aO H

H C N

N aC N

I

N aO H

M

(a) Give the structural formula of: H J K M

H is CHl3 J is CH3 COONa/CH3COO– K is

C H

C O HC H

C N

3

3

M is

C H C H

C CN H O HC H C Ho r

C l N H

3 3

3 32

2

(1 )

(b) Identify: Reagent1/2/3Reagent 1 Named dilute acid e.g. HCl(aq) or NaOH (aq) then add HCl

Reagent 2 PCl5 / SOCl2 / PCl3 Reagent 3 (Conc) ammonia (solution) / NH3

(c) Compounds produced when glucose C6H12O6, is metabolised include:CH2(OH)CH(OH)CHO CH3COCOOH CH3CH(OH)COOH2,3-dihydroxypropanal 2-oxopropanoic acid 2-hydroxypropanoic acid

(i) Draw the full structural formula for 2,3-dihydroxypropanal.HH H

C C C OC

O H O H (1 )(ii) Suggest two of these compounds which would give a positive test with 2,4-dinitrophenylhydrazine solution. State what you would see for a positive test result.

2,3-dihydroxypropanal and 2-oxopropanoic acid yellow / orange / orange–red ppt / solid / crystals

(iii) Describe a test which would enable you to distinguish between the two compounds identified in part (ii).Add Fehlings’ solution/ Benedicts’ solution red/orange ppt for2,3-dihydroxypropanal and no result for 2-oxopropanoic acid

Add ammoniacal silver nitrate silver mirror for2,3dihydroxypropanal and no result for 2-oxopropanoic acid

Add named carbonate effervescence/ bubbling for 2-oxopropanoic acid and no result for2,3-dihydroxypropanal

Add iodine + sodium hydroxide solution / Kl + NaClOyellow ppt for 2-oxopropanoic acid and no result for 2,3-dihydroxypropanal

Add dilute sulphuric acid + potassium dichromate dichromate goes green for 2,3-dihydroxypropanal and no result for 2-oxopropanoic acid

Draw two diagrams to clearly represent the optical isomers that result from the chirality of this alcohol C4H9OH

C C

H HO H H O

C H C H

C H C H5 5

3 3

2 2

(b) Alcohols react with carboxylic acids to form esters. Write an equation for a typical esterification reaction.CH3COOH + C2H5OH CH3COOC2H5 + H2O

(ii) Suggest how this type of reaction could be used to form polyestersAlcohol group at one end and acid group at the other React at each end

(iii) Give another type of reagent that could be used to make an ester from an alcoholAcyl chlorides / acid chlorides / acid halides / RCOCl / acid anhydride

(a) (i) Give the structural formula of a nitrile, C4H7N, that has an unbranched chain.H H H

C C C CH N

H H H

(1 )

(ii) Primary amines can be made by reducing nitriles. Suggest a reagent that could be used for this purpose.LiAlH4

(iii) Draw the structural formula of the amine produced by reducing the nitrile given in (a)(i).

H

H

H H H H

C C C CH N

H H H H

(1 )

(b) Draw the structure of an isomer of C4H11N which has a chiral centre in the molecule and identify the chiral centre

H

H

H

H

H

C

C

C

H

CH

H

N

H H H

*

(c) (i) What feature of an amine molecule makes it both a base and a nucleophile?lone pair of electrons on the N atom

(ii) Give, by writing an equation, an example of an amine acting as a base.C4H9NH2 + H+ C4H9NH3

+

(d) Ethanoyl chloride, CH3COCl, reacts with both amines and alcohols.(i) Give the name of the type of compound produced when ethanoyl chloride reacts with ethylamine, C2H5NH2

Amide

(ii) State one of the advantages of reacting ethanoyl chloride with ethanol to make an ester rather than reacting ethanoic acid with ethanol.

faster / more control / better yield / not equilibrium / no need to heat

(e) Ethanoyl chloride can be made from ethanoic acid.Suggest a reagent suitable for this conversion.PCl5 / PCl3 SOCl2

(ii) Suggest how chloromethane can be converted into ethanoic acid via a Grignard reagent.

3

3 2

2

2

3 2

4

2 7

23 3C H C l C H M g C l C H C O O H

M g /drye th er

(1 )(1)

C O a c id

(1 )(1 )

H C H Oac id (1 )

K C r OH S O

C H C H O H

C H C O H

(1 ) fo r a ll o fth e s tep san d reag e n tsap ar t fro macid w h ic h iss ta n d a lo n e

(a) Three isomers A, B and B have the molecular formula C4H8O.All three compounds give an orange precipitate with 2,4-dinitrophenylhydrazine reagent. B and C also give a silver mirror when warmed with ammoniacal silver nitrate solution. Write the structural formulae of A, B and C .A is CH3CH2COCH3 B and C are CH3CH2CH2CHO and CH3CH(CH3)CHO

(b) Substance A reacts with the Grignard reagent, C2H5MgBr. Give the equation for the preparation of this Grignard reagent.C2H5Br + Mg C2H5MgBr

(ii) State the conditions for this preparation dry ether (iii) Write the structural formula of the product obtained when this Grignard reagent reacts with substance A.

CH3CH2C(OH)(CH3) C2H5

(c) C2H5MgBr reacts with carbon dioxide to form the acid C2H5COOH, converted to propanamide in a two step process.

C2H5COOH

s tep 1 C2H5COCl

s tep 2 C2H5CONH2 State the reagent required for each step

step 1 PCl5 /PCl3 SOCl2 step 2 NH3

(d) C2H5MgBr also reacts with ethanal to form substance D, which exists as a pair of optical isomers(i) Draw the structural formulae of these two isomers and use them to explain why these isomers exist

C H C H

C C

H HC H C HO H H O

2 25 5

3 3

Has asymmetric carbon atom (4 diff groups on a carbon) mirror image non-superimposable

(ii) What is the difference in property between these isomers? rotate the plane of plane polarised light in opposite directions(e)(i) Write down the name and the structural formula of the organic compound formed when substance D is heated under reflux with a solution of potassium dichromate(VI) in dilute sulphuric acid.Name and Structural formula. State the colour of the solution remaining after this reaction

Butanone CH3CH2COCH3 green

(b) (i) Draw the structural formula of the secondary alcohol, C5H12O, which does NOT exist as optical isomers.H

H H H

H

O H H

H H H

C C C CCH H

(ii) X is obtained by oxidising this secondary alcohol with potassium dichromate(VI) acidified with dilute sulphuric acid.Draw the structural formula of X.

H

H H H HO

H H H

H HC C C C C

(v) X does not give a yellow precipitate when treated with iodine in the presence of sodium hydroxide solution. Explain why notno CH3CO / CH3CH(OH) / methyl ketone / methyl secondary alcohol present

C H O C H O A B

K C r O ind ilu te s u lp hu r ica c id

C D

3

2 2 7

38 6

c o nc s u lp h ur ic a c id

H B r

•None of the compounds in the scheme shows cis-trans isomerism•D reacts with KCN to form 2-methylpropanonitrile•An isomer of A will form C by the same route but will not produce B by reaction with potassium dichromate(VI) acidified with (dil) H2SO4 Instead it makes E, C3H6O2

Identify using a name or structural formulae:A,B,C,D,E

A Propan-2-ol B Propanone C Propene D 2-bromopropane E Propanoic acid

Ethanol can be converted into ethylamine by two different routes.

(a) Identify organic compounds V and W by writing their full structural formulae showing all bonds.

(b) Identify the reagents used in Steps A to EStep A: NH3 Step B: K2Cr2O7 and H2SO4 Step C: PCl5 OR SOCl2 OR PCl3

Step D: P2O5 OR P4O10 Step E: LiAlH4

(c) (i) What type of organic compound would be formed when ethylamine, CH3CH2NH2 reacts with ethanoyl chloride, CH3COCl?(N-substituted) amide(ii) A polymer is formed when the two monomers shown below react together under suitable conditions.

H2N(CH2)6NH2 ClOC(CH2)4COCl Draw sufficient of the polymer chain to make its structure clear.

An organic compound, A, with molecular formula C5H10O contains a carbonyl group.(a) Compound A is reacted with iodine in the presence of alkali. A pale yellow precipitate forms.(i) What is the formula of this precipitate? CHI3

(ii) What does this reaction indicate about the structure of A? methyl ketone(iii) Compound A has a branched carbon chain. Draw the structural formula and give the name of A

methylbutanone (b) Pentanal is a structural isomer of A. When heated with Fehling’s solution, it reacts to produce sodium pentanoate and a red precipitate.(i) Identify the homologous series to which pentanal belongs. aldehyde(ii) Suggest the identity of the red precipitate formed in this reaction. copper(I) oxide(c) State a reagent which could be used to convert the sodium pentanoate made in the reaction above into pentanoic acid.

Conc HCl/conc H2SO4

(d) Solid sodium hydrogencarbonate, NaHCO3, is reacted with excess concentrated pentanoic acid solution.(i) State what you would see as this reaction proceeds. effervescence/fizzing/bubbles(ii) Write a balanced chemical equation for this reaction CH3(CH2)3COOH + NaHCO3 → CH3(CH2)3COONa + H2O +

CO23. Two compounds, A and B, are isomers with molecular formula C4H8O.• A and B give an orange-yellow precipitate with 2,4-dinitrophenylhydrazine.• Both compounds react with sodium borohydride (sodium tetrahydridoborate(III)).• When the compounds are warmed separately with Fehling’s solution, A forms a red-brown precipitate but B does not.• Compound B forms yellow crystals when warmed with aqueous iodine and sodium hydroxide, whereas A does not.(a) Draw full structural formulae for A and B, showing all bonds.

A BGive name and formula for the organic product of the reaction between compound B and sodium borohydride in waterbutan(-)2(-)ol CH3CH(OH)C2H5

(e) Compound C has the molecular formula C4H8O.• When phosphorus pentachloride, PCl5, was added to a dry sample of C, steamy fumes were observed.• When bromine water was shaken with a sample of C, the bromine water turned colourless.• Compound C can be oxidised to a carboxylic acid which has a geometric isomer.Use the information above to draw the formulae of the two isomers which could be compound C

Cinnamaldehyde (a) To show the presence of the carbonyl group, a few drops of a solution of 2,4-dinitrophenylhydrazine are added to a sample of cinnamaldehyde.(i) What observation is made in the reaction above? yellow / orange/red and precipitate / crystals / solid(iii) Suggest a further reaction, including the result, to show that cinnamaldehydecontains an aldehyde group.(warm with) Fehling’s/Benedict’s solution, red ppt(iv) Why does the reaction you have given in (iii) not give a positive result with a ketone? ketone cannot be oxidised(b) Cinnamaldehyde can be converted into compound A

(i) Give the reagents and conditions which bring about this conversion. HCN+base or KCN+acid(ii) State, with a reason, how many stereoisomers exist for compound A. Four(c) Compound A reacts with lithium tetrahydridoaluminate(III), LiAlH4. The mixture is then treated with dilute acid to give the final organic product. (i) Name the type of reaction occurring between compound A and LiAlH4. reduction (ii) Draw the structural formula of the final organic product. C6H5CH=CHCH(OH)CH2NH2 (d) Cinnamaldehyde reacts with the Grignard reagent ethyl magnesium bromide, C2H5MgBr.(iii) Draw the structural formula of product formed when cinnamaldehyde reacts with C2H5MgBr, and the intermediate is hydrolysed.

C6H5CH=CHCH(OH)CH2CH3 (iv) State the type of alcohol formed in (d)(iii) Secondary