Topic 5 - INTEC Chemistry Blog



Topic 5.5: Organic chemistry IV (analysis, synthesis and application) Needs Units 2.2, 4.5 and 5.3

|Organic analysis – Tests for presence of these functional groups: |Tests to distinguish between primary, secondary and tertiary alcohols |

| |Tests for the halide group, by alkaline hydrolysis, then acidification, then testing with |

| |silver nitrate(aq) |

| |Must know reactions of |

| |bromine solution, |

| |phosphorus pentachloride, |

| |2,4-dinitrophenylhydrazine solution, |

| |Fehling’s solution |

| |ammoniacal silver nitrate, |

| |sodium or potassium hydrogencarbonate, |

| |iodine in the presence of alkali (or potassium iodide and sodium chlorate(I)) solution |

| | |

| | |

| | |

| | |

| | |

| | |

| | |

| | |

|functional group |reagent conditions |result of positive test |

|-C=C-  |bromine in inert solvent  |orange bromine decolourised  |

|-Cl  |warm with NaOH(aq) |white ppt. of AgCl |

| |add HNO3 then AgNO3 then NH3 (aq) |soluble in dil. NH3 (aq)  |

|-Br  |warm with NaOH(aq) |cream ppt. of AgBr |

| |add HNO3 then AgNO3 then NH3 (aq) |soluble in conc NH3 (aq)  |

|-I  |warm with NaOH(aq) |yellow ppt. of AgI |

| |add HNO3 then AgNO3 then NH3 (aq) |Insoluble in conc NH3 (aq)  |

|-OH  |add solid PCl5 |acrid steamy fumes of HCl |

|primary |warm with acidified aqueous  |orange colour changes to  |

|-CH2-OH |potassium dichromate K2Cr2O7 |green product tests +ve for |

| | |-CHO |

|secondary |warm with acidified aqueous conc. |orange colour changes to green  |

|-CH-OH |potassium dichromate K2Cr2O7 |product does not test +ve for |

|  | | |-CHO |

|tertiary |warm with acidified aqueous conc. |no change |

|  | |potassium dichromate K2Cr2O7 | |

|-C-OH | | |

|  | | | |

|-C=O  |add 2,4-dinitrophenylhydrazine |yellow ppt. of hydrazone |

|  | |warm with Fehling's solution  |no change in blue colour  |

|-CHO  |add 2,4-dinitrophenylhydrazine |yellow ppt. of hydrazone |

| |warm with Fehling's solution  |red/brown ppt of Cu2O forms |

| | |  |

| |warm with AgNO3(aq) in NH3(aq) |silver mirror forms |

|-COOH  |add NaHCO3 |effervescence CO2 formed  |

|-C=O   -CH-OH |add iodine then aqueous NaOH |yellow ppt. and |

|  |           | | |antiseptic smell of iodoform |

| CH3      CH3   | | |

|ethanal ethanol | | |

ii Use physical/chemical data to find the structural formula of a compound

iii a interpret simple fragmentation patterns from a mass spectrometer

b interpret simple infra-red spectra

c interpret simple low-resolution nuclear magnetic resonance spectra limited to proton magnetic resonance

d interpret simple ultra-violet/visible spectra.

students will not be expected to describe the theory of or the apparatus connected with the production of uv – visible, infra-red or nuclear magnetic resonance spectra

students will be given tables of data as appropriate.

students will not be expected to recall specific spectral patterns and/or wave numbers, but may be required to inspect given spectra and tables of data to draw conclusions

Organic synthesis

i propose practicable pathways for the synthesis of organic molecules

5.5a(iii)(a) interpret simple fragmentation patterns from a mass spectrometer

The large peak on the right is the parent molecular ion and this indicates the relative molecular mass of the compound. 

Compound of relative molecular mass 46, each fragment labelled and the structural formula

[pic]

1-bromopropane Ethanoyl chloride

[pic][pic]

5.5a (iii) (b) interpret simple infra-red spectra

The bonds in organic molecule absorb infra-red radiation. 

This happens when the frequency of the radiation matches the natural frequency of vibrations in the bonds. 

A spectrometer shines infra-red light at a sample of an organic material and measures how much of the light is absorbed. 

A measure of the frequency (wavenumber) is displayed in the spectrum.  Each bond has its own frequency (wavenumber) and this can be used to identify the bonds present in a compound.

|bond |wavenumber/cm-1 seen on |

| |spectrum |

|C-H |2840 – 3095 |

| C-C |1610 – 1680 |

|C=O |1680 – 1750 |

|C-O |1000 – 1300 |

|C-Cl |700 – 800 |

|O-H |3233 - 3550 |

| |2500 – 3300 |

|N-H |3100 – 3500 |

Ethanamide Ethanoic acid

[pic][pic]

5.5a(iii)(c) Low resolution nuclear magnetic resonance spectra (NMR)

The chemical shift is the difference between the absorption frequencies of the hydrogen nuclei in the compound and those in the reference compound

Nuclei are placed in a strong magnetic field and then absorb applied radio frequency radiation

The nuclei of hydrogen atoms in different chemical environments within a molecule will have different chemical shifts

The hydrogen nuclei in a CH3 group will have a different chemical shift from those in a CH2 or in an OH group.

In low resolution NMR, each group will show as a single peak, and the area under the peak is proportional to the number of hydrogen atoms in the same environment.

Thus ethanol, CH3CH2OH will have three peaks of relative intensities 3:2:1

Methyl propane CH3CH(CH3)CH3 will have two peaks with relative intensities of 9:1

In high resolution NMR spin coupling is observed. This is caused by the interference of the magnetic fields of neighbouring hydrogen nuclei.

If an adiacent carbon atom has hydrogen atoms bonded to it, they will cause the peaks to split as follows:

1 neighbouring H atom peak splits into 2 lines (a doublet)

2 neighbouring H atoms peak splits into 3 lines (a triplet)

n neighbouring H atoms peak splits into (n + 1) lines

Thus ethanol gives three peaks:

1 peak due to the OH hydrogen, which is a single line (as it is hydrogen bonded)

1 peak due to the CH2 hydrogens, which is split into four lines by the three H atoms on the neighbouring CH3 group.

1 peak due to the CH3 hydrogens, which is split into three lines by the two H atoms on the neighbouring CH2 group.

|Type of |Chemical Shift |

|proton |(ppm) |

|R-CH3 |0.9 |

|R-CH2 |1.3 |

|R-CH2-O- |4.0 |

|C6H5- |7.5 |

|-O-H |5.0 |

|-CHO |9.5 |

[pic]

5.5a (iii) (d) The interpretation of simple ultra-violet/visible spectra.

 Some chemical structures absorb electromagnetic radiation in the ultra violet part of the spectrum. 

These include conjugated (contain alternate double and single bonds) dienes.  E.g. 1,3-butadiene. 

The ultraviolet absorption spectrum for 2,5-dimethyl-2,4-hexadiene is shown below.

[pic]

Ultra-violet wavelengths are from about 200nm to about 400nm. 

Visible light has wavelength between 400nm and 800nm.  β-carotene, which gives carrots their orange colour absorbs at 497nm. 

Lycopene, which gives tomatoes their red colour, absorbs at 505nm. 

Both of these compounds have 11 conjugated double bonds.

5.5b(i)Pathways for organic synthesis

|Compound |Reagent |Conditions |Product |Reaction type |

|Alkane |Halogen |UV light |Haloalkane |Substitution |

| |bromine  |ethane  |bromoethane  | |

| |Br2 |C2H6 |CH3CH2Br | |

|Alkene |Halogen |ethene  |Decolourised from orange to colourless|Addition |

| |bromine  |C2H4 |Dihaloalkane | |

| |Br2 | |1,2-dibromoethane  | |

| | | |CH2BrCH2Br | |

| |Hydrogen halide |prop-1-ene  |Haloalkane |Electrophilic addition |

| |Hydrogen bromide |CH3CHCH2 |2-bromopropane  | |

| |HBr | |CH3CHBrCH3 | |

| |Alkaline(purple) |ethene  |Alcohol |Reduction |

| |potassium manganate(VII) |C2H4 |ethane-1,2-diol  | |

| |KMnO4 | |CH2OHCH2OH | |

| | H2SO4 | |Alcohol |Electrophilic addition |

|Haloalkane |NaOH(aq) or KOH(aq) |bromoethane  |Alcohol |Nucleophilic |

| | |C2H5Br |ethanol  |substitution |

| | | |C2H5OH | |

| |NaOH(ethanol) or KOH(ethanol) |Ethanolic solution |Alkene |Elimination |

| | |bromoethane  |ethene  | |

| | |C2H5Br |C2H4 | |

| |Potassium cyanide |Heat under reflux |Nitrile |Nucleophilic |

| |KCN(ethanol) |Ethanolic solution |propanonitrile  |substitution |

| | |bromoethane  |C2H5CN | |

| | |C2H5Br | | |

| |Ammonia |bromoethane  |amine  | |

| | |C2H5Br |ethylamine | |

| | | |C2H5NH2   | |

| |Mg |Dry ether(reflux) |Grignard reagent | |

| | |(Ether must be perfectly |C2H5MgBr | |

| | |dry since water destroys | | |

| | |resulting Grignard | | |

| | |reagent) | | |

| | |bromoethane  | | |

| | |C2H5Br | | |

| |Heat under reflux with NaOH | |ppt of silver halide | |

| |Acidify with dilute nitric acid |Chlorides |white ppt, soluble in dil NH3 | |

| |Add silver nitrate |Bromides |cream ppt, souble in conc NH3 | |

| | |Iodides |yellow ppt, insoluble in conc NH3 | |

|Alcohol |Combustion | |Carbon dioxide and water | |

| |PCl5 |dry |Haloalkane, steamy fumes of HCl | |

| | |ethanol  |chloroethane  | |

| | |C2H5OH |C2H5Cl + POCl3 + HCl | |

| |Hydrogen halide |ethanol  |Haloalkane | |

| |Hydrogen bromide |C2H5OH |bromoethane  | |

| |HBr | |C2H5Br | |

| |carboxylic acid  |concentrated H2SO4 |ester | |

| |ethanoic acid  |ethanol  |ethyl ethanoate  | |

| |CH3COOH |C2H5OH |CH3COOC2H5 | |

| |acid chloride  |ethanol  | | |

| |ethanoyl chloride  |C2H5OH | | |

| |CH3COCl | | | |

|Primary alcohol |potassium dichromate VI(orange) |Heat and distil off |(green) aldehyde that will react with | |

| |dilute sulphuric acid |product |Tollens reagent to give a silver | |

| | |ethanol  |mirror | |

| | |C2H5OH |ethanal  | |

| | | |CH3CHO | |

|Secondary alcohol | |concentrated H2SO4 |(green) ketone will not react with | |

| | |Heat under reflux |Tollens reagent | |

| | |propan-2-ol  |propanone  | |

| | |CH3CH(OH)CH3 |CH3COCH3 | |

|Tertiary alcohol | | |(orange) no reaction | |

|Grignard reagent |Water | |Alkane RH |Nucleophilic |

|RMgX | | | |substitution |

| |Carbon dioxide |C2H5MgBr |Carboxylic acid RCOOH | |

| | | |propanoic acid  | |

| | | |C2H5COOH | |

| |Methanal | |Primary alcohol RCH2OH | |

| |HCHO | |propan-1-ol  | |

| | | |C2H5CH2OH | |

| |Aldehydes R1CHO | |Secondary alcohol RCH(OH)R1 | |

| |ethanal  | |butan-2-ol  | |

| |CH3CHO | |CH3CH2CH(OH)CH3 | |

| |Ketones R1COR2 | |Tertiary alcohol RR1R2COH | |

| |propan-2-one  | |2-methylpropan-2-ol  | |

| |(CH3)2CO | |(CH3)3OH | |

|Carboxylic acids RCOOH |Alcohol R1OH |Heat |Ester RCOOR1 |Nucleophilic |

| |ethanol  |concentrated H2SO4 |ethyl ethanoate  |substitution followed by|

| |C2H5OH |ethanoic acid  |CH3COOC2H5 |elimination |

| | |CH3COOH | | |

| |Lithium aluminium hydride |Dry ether |Alcohol RCH2OH |Reduction |

| |LiAlH4 |ethanoic acid  |ethanol  | |

| | |CH3COOH |C2H5OH | |

| |Phosphorus pentachloride |Dry |Acid chloride RCOCl |Nucleophilic |

| |PCl5 |ethanoic acid  |ethanoyl chloride  |substitution |

| | |CH3COOH |CH3COCl | |

| |Sodium carbonate/hydrogen carbonate |ethanoic acid  |Sodium salt RCOO-Na+ |Acid-base |

| |Na2CO3 and NaHCO3 |CH3COOH |CO2 gas(gives white ppt with | |

| | | |limewater) | |

| | | |sodium ethanoate | |

| | | |CH3COONa | |

|Esters RCOOR1 |concentrated H2SO4 |ethyl ethanoate  |Alcohol R1OH and acid RCOOH |Hydrolysis (equil) |

| | |CH3COOC2H5 |ethanol, ethanoic acid  | |

| | | |C2H5OH, CH3COOH | |

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

| | | |ethanol, sodium ethanoate | |

| | | |C2H5OH, CH3COONa | |

|Aldehydes RCHO or |Hydrogen cyanide(HCN(covalent)) and |ethanal  |Cyanohydrin RCH(OH)CN or RR1C(OH)CN |Nucleophilic |

|ketones RCOR1 |potassium cyanide |CH3CHO |CH3CH(OH)(CN) |substitution |

| | |or |or | |

| | |propanone  |CH3C(OH)(CH3)CN | |

| | |(CH3)2CO | | |

| |2, 4-dinitrophenylhydrazine |Dilute sulphuric acid |2, 4-dinitrophenylhydrazine |Nucleophilic |

| |Test for carbonyl(C=O) group | |(Orange ppt) |substitution followed by|

| | | | |elimination |

| |Sodium borohydride NaBH4 or lithium |ethanal  |Primary alcohol RCH2OH or secondary |Reduction |

| |aluminium hydride LiAlH4 |CH3CHO |alcohol RCH(OH)R1 | |

| | | |Primary alcohol, ethanol  C2H5OH | |

| | |or |or | |

| | |propanone  |Secondary alcohol propan-2-ol  | |

| | |(CH3)2CO |CH3CH(OH)CH3 | |

|Aldehydes RCHO (not |Ammonical silver nitrate solution (Tollens |Warm in water bath |Silver mirror |Reduction of the silver |

|ketones) |reagent) |ethanal  |Carboxylic acid |ion |

|Test for CHO group( | |CH3CHO |ethanoic acid  | |

| | | |CH3COOH | |

| |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 |Oxidation |

| |alkaline conditions | |salt RCOO-X | |

|Carbonyl compounds |NaOH + I2 |Heat |RCOONa + CHI3 (iodoform/yellow ppt) |Haloform |

|containing | | | | |

|CH3C=O and alcohols | | | | |

|containing CH3CH(OH) | | | | |

|Acid chlorides ROCl |Water |ethanoyl chloride  |Carboxylic acid |Nucleophilic |

| | |CH3COCl |ethanoic acid  |substitution |

| | | |CH3COOH | |

| |Ammonia | |Amide RCONH2 | |

| |NH3 | |ethanamide  | |

| | | |CH3CONH2 | |

| |Alcohol R1OH | |Ester RCOOR1 | |

| |ethanol | |ethyl ethanoate  | |

| |CH3CH2OH | |CH3COOC2H5 | |

| |Amine R1NH2 | |N- substituted amide R1CONHR | |

| |phenylamine  | |CH3CONHC6H5 | |

| |C6H5NH2 | | | |

|Amines RNH2 |Aqueous acid |ethylamine  |salt  RNH3+Cl- |Acid-base |

| |HCl(aq) |C2H5NH2 |C2H5NH3+Cl- | |

| |Acid chloride R1OCl | |N-substituted amide R1CONHR |Nucleophilic |

| |ethanoyl chloride | |CH3CONHC2H5 |substitution |

| |CH3COCl | | | |

|Amides RCONH2 |Phosphorus(V) oxide P4O10 |ethanamide  |Nitrile RCN |Dehydration |

| | |CH3CONH2 |ethanonitrile  | |

| | | |CH3CN | |

| |Bromine followed by NaOH(aq) | |Amine RNH2 |Substitution followed by|

| | | |methylamine  |rearrangement and |

| | | |CH3NH2 |elimination |

|Nitriles RCN |HCl(aq) |heat under reflux |Carboxylic acid |Hydrolysis |

| | |ethanonitrile  |ethanoic acid  | |

| | |CH3CN |CH3COOH | |

| |NaOH(aq) | |Salt RCOO-Na+ | |

| | | |sodium ethanoate  | |

| | | |CH3COONa | |

| |lithium aluminium hydride LiAlH4 |Dry ether |Amine RCH2NH2 |Reduction |

| | |ethanonitrile  |ethylamine  | |

| | |CH3CN |CH3CH2NH2 | |

|Amino acids |Aqueous acid eg HCl(aq) | |Salt RCH(NH3+)COOH |Acid-base |

|RCH(NH3+)COO- | | | | |

|Compound |Reagent |Conditions |Product |Reaction type |

|arene  |Nitrating mixture |heat under reflux  |nitrobenzene | |

|benzene  C6H6 |nitric acid  HNO3 |below 60oC  |C6H5NO2 + H2O | |

| |sulphuric acid H2SO4 | | | |

|arene  |Bromine |Catalyst (dry) Anhydrous |halogenoarene | |

|benzene  C6H6 |Br2 |AlCl3 |bromobenzene | |

| | | |C6H5Br(l)   + HBr(g) | |

|arene  |Chloroalkane |Catalyst (dry) Anhydrous |ethylbenzene | |

|benzene  C6H6 |Chloroethane C2H5Cl |AlCl3 |C6H5C2H5(l) + HCl(g) | |

|arene  |Acid chloride |Catalyst (dry) Anhydrous |Ketone | |

|benzene  C6H6 |Ethanoyl chloride CH3COCl |AlCl3 |phenylethanone | |

| | | |C6H5COCH3(l) + HCl(g) | |

|arene  |Potassium manganate VII |alkaline conditions  |Carboxylic acid | |

|methylbenzene  |KMnO4 |heat under reflux |benzoic acid  | |

|C6H5CH3 | | |C6H5COOH + H2O | |

|Aromatic nitro compounds|C6H5NO2 + 6H+ + 6e- (C6 H5NH2 + 2H2O |heated under reflux with |Amines | |

| |nitrobenzene                         |tin in conc. HCl as | | |

| |aminobenzene (phenylamine) |reducing agent | | |

|Phenol |Sodium hydroxide | |Sodium phenoxide | |

|C6H5OH |NaOH | |C6H5O-Na+(aq) + H2O(l) | |

|Phenol |Bromine | |C6H2Br3OH(aq) + 3HBr(aq) |substitution |

|C6H5OH |Br2 | |2,4,6-tribromophenol (TCP) | |

|Phenol |ethanoyl chloride   |Dry |ester | |

|C6H5OH |CH3COC | |CH3COOC6H5 + HCl | |

| | | |phenylethanoate | |

|Phenylamine |nitrous acid  |5oC |C6H5NH2 + HNO2 + HCl ( 2H2O  +  | |

|C6H5NH2 |HNO2 |NaNO2 and dil HCl situ |C6H5N2+Cl- | |

| | | |Diazonium ion | |

|Diazonium ion |phenol  |5oC |Yellow azo dye | |

|C6H5N2+Cl- |C6H5OH | |C6H5N2C6H5OH | |

ii propose suitable apparatus, conditions and safety precautions for carrying out organic syntheses, given suitable information

iii Know practical techniques used in organic chemistry

mixing, heating under reflux,

fractional distillation,

filtration under reduced pressure (filter pump and Buchner funnel),

recrystallisation,

determination of Mt & Bt

heating with a variety of sources, with safety and the specific hazards of the reaction/chemicals

it will be assumed that students wear eye protection during all practical work

iv demonstrate an understanding of the principles of fractional distillation in terms of the graphs of boiling point against composition.

students will not be expected to recall experimental procedures for obtaining graphs of boiling point against composition

knowledge of systems that form azeotropes will not be expected

Organic compounds may be hazardous because of

- Flammability - Avoid naked flames.  Use electrical heater, water bath.

- Toxicity – fume cupboards

|Separating a mixture of immiscible liquids (Separating a mixture of water and hexane) |

|Water and hexane are immiscible forming 2 separate layers and are separated using a separating funnel |

|Separating a solvent from solution Simple distillation |

|[pic] |

|Separating a liquid from a mixture of miscible liquids |

|Fractional distillation Separates mixtures of miscible liquids with different Bt’s, using a fractionating column increasing efficiency of redistillation process, packed with inert material(glass |

|beads) increasing surface area where vapour may condense. |

|- When mixture is boiled vapours of most volatile component(lowest Bt) rises into the vertical column where they condense to liquids. |

|- As they descend they are reheated to Bt by the hotter rising vapours of the next component. |

|- Boiling condensing process occurs repeatedly inside the column so there is a temperature gradient. |

|- Vapours of the more volatile components reach the top of the column and enter the condenser for collection |

|[pic] |Boiling under reflux is necessary when either the reactant has a low Bt or the |Solid can be identified from its Mt and Bt |

| |reaction is slow at RT |Solid must be purified by recrystallisation to have accurate Mt |

| |- condenses vapours and returns reagents to flask, prevents loss of |Impurities lower the melting point. |

| |reactants/products, prolonged heating for slow reactions |Thermometer doesn’t come into contact with the glass |

| |- For preparation of aldehyde/carboxylic acid from alcohol | |

| | |Recrystallisation |

| |(1)Reason for heating the mixture but then taking the flame away |Dissolve the solid in a minimum of hot solvent. |

| |(1)provide Ea, exothermic/prevent reaction getting out of control |Filter the hot solution through a preheated funnel using fluted filter paper. |

| | |Allow to cool. |

| | |Filter under reduced pressure (Buchner funnel), |

| | |Wash with a little cold solvent and allow to dry. |

c Applied organic chemistry

Know organic compounds use in pharmaceuticals, agricultural products and materials. Only need to know:

i changes to the relative lipid/water solubility of pharmaceuticals by the introduction of non-polar side-chains or ionic groups

ii the use of organic compounds such as urea as sources of nitrogen in agriculture and their advantages as compared with inorganic compounds containing nitrogen

iii the use of esters, oils and fats(from the viewpoint of saturation) , to include flavourings, margarine, soaps and essential oils,

Lipid/water solubility of pharrnaceutical .

Those which are ionic which can form hydrogen bonds with water, will tend to be retained in aqueous (non-fatty) tissue, and excreted

Compounds with no ionic groups and non-polar side chains, will be retained in fatty tissue and stored in the body

Esters - Food flavourings, perfumes, glues, varnishes and spray paints.

Fats - Soap

Oils - Margarine

iv properties and uses of addition polymers of ethene, propene, chloroethene, tetrafluoroethene and phenylethene, and of the condensation polymers (polyesters and polyamides).

this should include consideration of the difficulties concerned with the disposal of polymers

no specific reactions will be the subject of recall questions. Students will be expected to give some examples of compounds and reactions to illustrate their answers.

Polymers(Addition or condensation)

Addition polymer Monomers contain one or more C=C group

Ethene, polyethene plastic bags, bottles

Propene, polypropene ropes, sacks, carpets

Chloroethene, PVC Raincoats, electrical insulator, packaging

Tetrafluroethene non-stick coating on frying pans

Condensation polymer Both the monomers have 2 functional groups, one at each end.

Polyester Conveyor belt, safety belt

Polyamide Parachutes, brushes

Questions

|propenal [pic] |

|(a) (i) State what is observed when propenal reacts with 2,4-dinitrophenylhydrazine Yellow/orange precipitate |

|(b) Explain why propenal has three peaks in its low-resolution n.m.r. spectrum. Suggest the relative areas under these peaks. |

|( Hydrogen nuclei ( is in 3 different environments |

|( Ratio 2:1:1 |

|4. Phenylethanoic acid occurs naturally in honey as its ethyl ester: it is the main cause of the honey’s smell. The acid has the structure |

|[pic] Phenylethanoic acid can be synthesised from benzene as follows: |

|[pic] |

|(a) State the reagent and catalyst needed for step 1. Reagent: chloromethane/CH3Cl |

|Catalyst: (anhydrous) aluminium chloride/AlCl3/Al2Cl6 |

|(b) (i) What type of reaction is step 2? Free radical substitution |

| |

|(ii) Suggest a mechanism for step 2. The initiation step, the two propagation steps and a termination step. You may use Ph to represent the phenyl group, |

|C6H5. |

|Cl2 ( 2Cl• |

|PhCH3 + Cl• ( PhCH2• + HCl |

|PhCH2• + Cl2 ( PhCH2Cl + Cl• |

|2PhCH2• ( PhCH2CH2Ph OR PhCH2• + Cl• ( PhCH2Cl OR 2Cl• ( Cl2 |

|(iii) Draw an apparatus which would enable you to carry out step 2, in which chlorine is bubbled through boiling methylbenzene, safely. Do not show the uv |

|light source. |

|flask and vertical condenser – need not be shown as separate items [Ignore direction of water flow; penalise sealed condenser] |

|gas entry into liquid in flask [allow tube to go through the side of the flask, but tube must not be blocked by flask wall] |

|heating from a electric heater/heating mantle/sandbath/water bath/oil bath |

| |

|(c) (i) Give the structural formula of compound A. |

|[pic] |

|(ii) Give the reagent and the conditions needed to convert compound A into phenylethanoic acid in step 4. |

|HCl (aq) OR dilute H2SO4(aq) - Boil/heat (under reflux)/reflux |

|OR - NaOH(aq) and boil - Acidify |

| |

|(iii) Suggest how you would convert phenylethanoic acid into its ethyl ester. |

|ethanol and (conc) sulphuric acid |

|heat/warm/boil/reflux conditional on presence of ethanol |

|OR - PCl5 /PCl3/SOCl2 |

|- Add ethanol PCl5 and ethanol (1) PCl5 in ethanol (0) |

| |

|(d) (i) An isomer, X, of phenylethanoic acid has the molecular formula C8H8O2. This isomer has a mass spectrum with a large peak at m/e 105 and a molecular |

|ion peak at m/e 136. The ring in X is monosubstituted. Suggest the formula of the ion at m/e 105 and hence the formula of X. |

| |

|[pic] X is [pic] OR [pic] |

| |

|(ii) Another isomer, Y, of phenylethanoic acid is boiled with alkaline potassium manganate(VII) solution and the mixture is then acidified. The substance |

|produced is benzene-1,4-dicarboxylic acid: |

|[pic]Suggest with a reason the structure of Y. [pic]Side-chain(s) oxidised to COOH |

| |

|(e) Benzene-1,4-dicarboxylic acid can be converted into its acid chloride, the structural formula of which is |

|[pic]This will react with ethane-1,2-diol to give the polyester known as PET. |

|(i) What reagent could be used to convert benzene-1,4-dicarboxylic acid into its acid chloride? |

|PCl5 /Phosphorus pentachloride/phosphorus(V) chloride |

|OR PCl3/ Phosphorus trichloride/phosphorus(III) chloride |

|OR SOCl2/Thionyl chloride/sulphur oxide dichloride |

| |

|(ii) Give the structure of the repeating unit of PET. |

|[pic] |

|(iii) Suggest, with a reason, a type of chemical substance which should not be stored in a bottle made of PET. |

|(concentrated) acid/alkali (ester link) would be hydrolysed OR polymer would react to form the monomers/alcohol and acid |

|1. A chemist has synthesised a compound W believed to be |

|[pic] |

|(a) State and explain what you would see if W is reacted with: (i) sodium carbonate solution ( effervescence ( COOH present /acidic/contains H+ |

| |

|(ii) bromine water. ( Decolourises ( compound containsC=C/unsaturated ( white ppt so is a phenol |

| |

|(b) W shows both types of stereoisomerism. (i) How many stereoisomers of W are there? Briefly explain your answer |

|( Four ( (Two) cis/trans (or geometric), and (two) chiral/optical isomers/ enantiomers |

|OR ( Two cis-trans/geometric isomers ( Two optical isomers/enantiomers |

| |

|(ii) Explain why W shows optical isomerism |

|( Molecule has a chiral centre/chiral carbon/carbon with four different groups |

|( having non-superimposable mirror images |

|(c) Describe how you would show that W contains chlorine. |

|( NaOH (solution) |

|( acidify with /add excess HNO3 |

|( add silver nitrate (solution) |

|( white precipitate |

|( soluble in dilute/aqueous ammonia |

|5. Consider the reaction scheme below, which shows how the compound methyl methacrylate, CH2=C(CH3)COOCH3, is prepared industrially from propanone |

|[pic] (a) (i) State the type of reaction which occurs in Step 2. Elimination/dehydration |

|(ii) Name the reagent in Step 2. Concentrated sulphuric acid / concentrated phosphoric acid / aluminium oxide |

|(iii) State the type of reaction which occurs in Step 3. hydrolysis |

|(iv) State the type of reaction which occurs in Step 4. eterification |

|(v) Give the organic reagent required for Step 4. methanol |

|(b) (i) Give the mechanism for the reaction in Step 1 between the hydrogen cyanide and propanone. |

|[pic] OR [pic] |

|(ii) The reaction in (b)(i) is carried out at a carefully controlled pH. Given that hydrogen cyanide is a weak acid, suggest why this reaction occurs more |

|slowly at both high and low concentrations of hydrogen ions. |

|( High [H+] insufficient CN- (available for nucleophilic attack) |

|( Low [H+] insufficient H+ / HCN for the second stage |

|( High [[H+] surpresses ionisation / shifts equilibrium to left and low [H+] shifts equilibrium to right max |

| |

|(c) Methyl methacrylate polymerises in a homolytic addition reaction to form the industrially important plastic, Perspex. |

|(i) Identify the type of species that initiates this polymerisation. Free radical/peroxide |

|(ii) Draw a sufficient length of the Perspex polymer chain to make its structure clear. |

|[pic] |

|(iii) Suggest why it is not possible to quote an exact value for the molar mass of Perspex, but only an average value. |

|The polymer chain lengths are different (due to different termination steps) / different size molecules/ different numbers of monomer (units) |

|4. (a) (i) Describe the appearance of the organic product obtained when an aqueous solution of bromine is added to aqueous phenol. |

|White ppt |

|(ii) Give the equation for the reaction in (a)(i). |

|[pic] [pic] |

|(iii) Phenol reacts with ethanoyl chloride to form an ester. Complete the structural formula to show the ester produced in this reaction. |

|[pic] [pic] |

|(iv) Suggest, in terms of the bonding in ethanoyl chloride, why the reaction in (a)(iii) proceeds without the need for heat or a catalyst. |

|( C (atom) is (very) δ+ because Cl highly electronegative OR Cl electron withdrawing |

|( (so C atom) susceptible to nucleophilic attack OR (so C atom) strongly electrophilic |

|(b) Phenylamine, C6H5NH2, is formed by the reduction of nitrobenzene, C6H5NH2 Give the reagents which are used |

|Sn and HCl acid OR Fe and HCl acid |

|(c) Phenylamine is used to prepare azo dyes. (i) State the reagents needed to convert phenylamine into benzenediazonium chloride. |

|• Sodium nitrite OR NaNO2 OR sodium nitrate(III) |

|• HCl acid OR dilute sulphuric acid OR aqueous sulphuric acid |

|(ii) The reaction in (c)(i) is carried out at a temperature maintained between 0 °C and 5 °C. Explain why this is so. |

| |

|(iii) Addition of benzenediazonium chloride solution to an alkaline solution of phenol gives a precipitate of the brightly coloured dye, 4-hydroxyazobenzene. |

|Give the structural formula of 4-hydroxyazobenzene. |

|( Below 0°C : reaction too slow |

|( Above 5°C : product decomposes OR diazonium ion decomposes |

|(iv) Describe how recrystallisation is used to purify a sample of the solid dye formed in (c)(iii). |

|( Dissolve in minimum volume of boiling/hot solvent NOT “small volume” |

|( Filter hot OR filter through heated funnel |

|( Cool or leave to crystallise |

|( Filter (under suction) |

|( Wash solid with cold small volume of solvent (and leave to dry) |

|[pic] |

|(a) (i) State the catalyst that is needed for Step 1 aluminium chloride/AlCl3/Al2Cl6 / iron(III) chloride/FeCl3 |

| |

|(ii) Suggest a synthetic pathway that would enable you to make ethanoyl chloride from ethanol in two steps. You should give reagents, conditions and the |

|structure of the intermediate compound. Experimental details and balanced equations are not required. |

| |

|( First step Potassium dichromate +sulphuric acid OR acidified dichromate OR H+ + Cr2O72- OR (potassium) manganate(VII)/permanganate + |

|acid/alkali/neutral |

|( heat / reflux |

|( Intermediate: CH3COOH/CH3CO2H |

|( Second step PCl5 / PCI3 / SOCl2 |

| |

|(b) Give the reagents and conditions needed for, step 2 & 3 Step 2 ( LiAlH4 ( dry ether / ethoxyethane (followed by hydrolysis) |

|OR ( NaBH4 ( aqueous ethanol/water |

|OR ( Na ( ethanol |

|OR ( H2 ( Pt OR Ni+heat OR Ni + specified temperature |

|Step 3 ( KMnO4 ( NaOH/ alkali ( Heat |

|OR ( I2 ( NaOH ( warm |

|The IR spectra for compounds A and B are shown. |

|[pic][pic] |

|[pic] |

|(i) Using Table 1, give evidence from the spectra which shows that compound A has been reduced, comment on both spectra |

| |

|( A, spectrum shows bond due to C=O at 1680-1700cm– 1 ( B, spectrum shows bond due to OH at 3230-3550cm– 1 |

|( A has no OH / no bond at 3230-3550 OR B has no C=O bond / no bond at 1680-1700 |

|(ii) Compound B is chiral. The IR spectra of the two optical isomers of B are identical. Suggest why this is so. |

| |

|( IR spectra due to bonds present ( Same bonds/functional groups in both isomers |

|(d) Both compounds A and B will react with iodine in sodium hydroxide solution to give a yellow precipitate of triiodomethane (iodoform). |

|(i) B is oxidised to A during the reaction. Suggest the identity of the oxidising agent. Iodine/I2/sodium iodate(I) / NaOI /NaIO/iodate(I)/ OI- /IO- |

| |

|(ii) Give the equation for the reaction of A with iodine in sodium hydroxide. |

| |

|C6H5COCH3 + 3I2 + 4OH – (C6H5COO – + CHI3 + 3I – + 3H2O OR C6H5COCH3 + 3I2 + 4NaOH ( C6H5COONa + CHI3 + 3NaI + 3H2O |

|(iii) Describe a chemical test to show that triiodomethane contains iodine. |

| |

|( (Hydrolyse with) NaOH / alkali ( acidify / neutralise with HNO3/ excess HNO3 ( add silver nitrate (solution) ( yellow ppt |

|4. (a) The following equation shows the reaction of propane with chlorine to produce 1-chloropropane CH3CH2CH3 + Cl2 → CH3CH2CH2Cl + HCl |

|(i) Name the mechanism of the above reaction free radical substitution |

|(ii) State ONE essential condition. UV radiation/sunlight/white light/heat |

|(b) The boiling temperature of 1-chloropropane is 46 °C and that of 1-bromopropane is 71 °C. |

|Draw a boiling temperature/composition diagram for a mixture of these two substances. Use it to explain how fractional distillation could be used to separate |

|this mixture |

| |

|Diagram labelled axes, lozenge and b.pt. values At least 2 horizontal + 2 vertical tie lines from anywhere except 100% |

|Explanation Vapour richer in more volatile/chloropropane Condense and then reboil |

|Pure chloropropane distilled off / bromopropane left as residue |

| |

|(c) Describe how to distinguish between pure samples of 1-chloropropane and 1-bromopropane using chemical tests. |

|heat with NaOH |

|add excess HNO3 OR acidify with HNO3 |

|add AgNO3 |

|chloro gives white and bromo gives cream ppt |

|white/off white/ pale yellow ppt soluble in dil NH3, cream ppt, slightly/partially soluble in dil NH3 , (or soluble in conc NH3) |

| |

|(d) Suggest which technique, mass spectrometry or low resolution n.m.r., would be used to distinguish between 1-chloropropane and 1-bromopropane. |

|MS shows different m/e values for molecular ion |

|Because molar masses different / or reason why different |

|Nmr give same number/3 peaks with both |

|OR Nmr shows different chemical shifts |

|Due to different halides |

|In MS molecular ion peak often absent |

| |

|5. (a) An acidified solution of potassium manganate(VII) contains MnO4– ions, and can oxidise bromide ions, Br–, to bromine. |

|It was found that 23.90 cm3 of 0.200 mol dm–3 potassium manganate(VII) solution was required to oxidise a solution containing 2.46 g of sodium bromide |

|dissolved in dilute sulphuric acid. |

|Calculate the ratio of the number of moles of manganate(VII) ions reacting to the number of moles of bromide ions reacting. |

|Hence write the equation for the oxidation of bromide ions by manganate(VII) ions in acid solution. |

| |

|Moles manganate = 0.0239 x 0.2 = 0.00478 |

|Moles bromide = 2.46/103 = 0.0239 |

|ratio MnO4− : Br− = 1:5 OR ratio Br− : MnO4− = 5:1 |

|MnO4- + 5Br- + 8H+ → Mn2+ + 4H2O + 2.5Br2 |

| |

|(b) Acidified potassium manganate(VII) solution can be safely stored in containers made of poly(ethene). |

|(i) Suggest a property of poly(ethene) which makes it suitable for the storage of this solution. |

| |

|Not oxidised by manganate(VII)/ does not react with oxidising agents OR Not hydrolysed by acid |

| |

|(ii) Explain ONE environmental problem which may be caused by the disposal of a poly(ethene) container. non-biodegradable therefore fills landfill sites |

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