Topic 5 Organic chemistry IV _analysis_ synthesis and application_

					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              - Tests to distinguish between primary, secondary and tertiary
functional groups:                                               alcohols
                                                            - Tests for the halide group, by alkaline hydrolysis, then
                                                                 acidification, then testing with silver nitrate(aq)
          C C                 C Cl             C Br               C I
                                                            - Must know reactions of
                                                                 bromine solution,
                                                                 phosphorus pentachloride,
             H               H                                   2,4-dinitrophenylhydrazine solution,
            C OH             C OH              C OH              Fehling’s solution
                                                                 ammoniacal silver nitrate,
             H                                                   sodium or potassium hydrogencarbonate,
                                  O                O             iodine in the presence of alkali (or potassium iodide and sodium
            C O                C                C       chlorate(I)) solution
                                      H             OH

                 O                H
             C                    C CH3
                 CH3
                                  OH


functional
                 reagent conditions         result of positive test
group
                                            orange bromine
-C=C-            bromine in inert solvent
                                            decolourised
                 warm with NaOH(aq)
                                            white ppt. of AgCl
-Cl              add HNO3 then AgNO3
                                            soluble in dil. NH3 (aq)
                 then NH3 (aq)
                 warm with NaOH(aq)
                                            cream ppt. of AgBr
-Br              add HNO3 then AgNO3
                                            soluble in conc NH3 (aq)
                 then NH3 (aq)
                 warm with NaOH(aq)
                                            yellow ppt. of AgI
-I               add HNO3 then AgNO3
                                            Insoluble in conc NH3 (aq)
                 then NH3 (aq)
-OH              add solid PCl5             acrid steamy fumes of HCl
                 warm with acidified
                                            orange colour changes to
primary          aqueous
                                            green product tests +ve for
-CH2-OH          potassium dichromate
                                            -CHO
                 K2Cr2O7
                                            orange colour changes to
                 warm with acidified
secondary                                   green
                 aqueous conc.
-CH-OH                                      product does not test +ve
                 potassium dichromate
 |                                          for
                 K2Cr2O7
                                            -CHO
tertiary         warm with acidified
  |              aqueous conc.
                                            no change
-C-OH            potassium dichromate
  |              K2Cr2O7
                 add 2,4-
-C=O             dinitrophenylhydrazine     yellow ppt. of hydrazone
 |               warm with Fehling's        no change in blue colour
                 solution
                 add 2,4-
                 dinitrophenylhydrazine     yellow ppt. of hydrazone
                 warm with Fehling's        red/brown ppt of Cu2O
-CHO             solution                   forms

                 warm with AgNO3(aq) in     silver mirror forms
                 NH3(aq)
-COOH          add NaHCO3                   effervescence CO2 formed
-C=O -CH-
OH
                                            yellow ppt. and
 |      | add iodine then aqueous
                                            antiseptic smell of
 CH3 CH3 NaOH
                                            iodoform
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




1-bromopropane                                                                                                        Ethanoyl
chloride
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.
       wavenumber/cm-1
bond
       seen on spectrum
C-H    2840 – 3095
C-C    1610 – 1680
C=O    1680 – 1750
C-O    1000 – 1300
C-Cl   700 – 800
       3233 - 3550
O-H
       2500 – 3300
N-H    3100 – 3500
Ethanamide                                                                                                 Ethanoic acid




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 CH 2 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
proton      Shift (ppm)
R-CH3       0.9
R-CH2       1.3
R-CH2-O- 4.0
C6H5-       7.5
-O-H        5.0
-CHO        9.5




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.




Ultra-violet wavelengths are from about 200nm to about 400nm.
Visible light has wavelength between 400nm and 800nm. -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     Addition
                   bromine                           C2H4                  colourless
                   Br2                                                     Dihaloalkane
                                                                           1,2-dibromoethane
                                                                           CH2BrCH2Br
                   Hydrogen halide                   prop-1-ene            Haloalkane                      Electrophilic
                   Hydrogen bromide                  CH3CHCH2              2-bromopropane                  addition
                   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        C2H5MgBr
                                                     perfectly 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
                                                     Iodides               NH3
                                                                           yellow ppt, insoluble in conc
                                                                           NH3
Alcohol            Combustion                                              Carbon dioxide and water
                   PCl5                              dry                   Haloalkane, steamy fumes of
                                                     ethanol               HCl
                                                     C2H5OH                chloroethane
                                                                           C2H5Cl + POCl3 + HCl
                   Hydrogen halide                   ethanol               Haloalkane
                   Hydrogen bromide                  C2H5OH                bromoethane
                   HBr                                                     C2H5Br
                   carboxylic acid                   concentrated          ester
                   ethanoic acid                     H2SO4                 ethyl ethanoate
                   CH3COOH                           ethanol               CH3COOC2H5
                                                     C2H5OH
                   acid chloride                     ethanol
                   ethanoyl chloride                 C2H5OH
                   CH3COCl
Primary alcohol    potassium dichromate VI(orange)   Heat and distil off   (green) aldehyde that will
                   dilute sulphuric acid             product               react with Tollens reagent to
                                                     ethanol               give a silver mirror
                                                     C2H5OH                ethanal
                                                                           CH3CHO
Secondary                                            concentrated          (green) ketone will not react
alcohol                                              H2SO4                 with Tollens reagent
                                                     Heat under reflux     propanone
                                                     propan-2-ol           CH3COCH3
Tertiary alcohol                                     CH3CH(OH)CH3          (orange) no reaction
Grignard reagent   Water                                                    Alkane RH                      Nucleophilic
RMgX               Carbon dioxide                      C2H5MgBr             Carboxylic acid RCOOH          substitution
                                                                            propanoic acid
                                                                            C2H5COOH
                   Methanal                                                 Primary alcohol RCH2OH
                   HCHO                                                     propan-1-ol
                                                                            C2H5CH2OH
                   Aldehydes R1CHO                                          Secondary alcohol
                   ethanal                                                  RCH(OH)R1
                   CH3CHO                                                   butan-2-ol
                                                                            CH3CH2CH(OH)CH3
                   Ketones R1COR2                                           Tertiary alcohol RR1R2COH
                   propan-2-one                                             2-methylpropan-2-ol
                   (CH3)2CO                                                 (CH3)3OH
Carboxylic acids   Alcohol R1OH                        Heat                 Ester RCOOR1                   Nucleophilic
RCOOH              ethanol                             concentrated         ethyl ethanoate                substitution
                   C2H5OH                              H2SO4                CH3COOC2H5                     followed by
                                                       ethanoic acid                                       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           ethanoic acid        Sodium salt RCOO-Na+           Acid-base
                   carbonate                           CH3COOH              CO2 gas(gives white ppt with
                   Na2CO3 and NaHCO3                                        limewater)
                                                                            sodium ethanoate
                                                                            CH3COONa
Esters RCOOR1      concentrated H2SO4                  ethyl ethanoate      Alcohol R1OH and acid          Hydrolysis (equil)
                                                       CH3COOC2H5           RCOOH
                                                                            ethanol, ethanoic acid
                                                                            C2H5OH, CH3COOH
                   NaOH(aq)                                                 Alcohol R1OH and salt          Hydrolysis (equil)
                                                                            RCOO-Na+
                                                                            ethanol, sodium ethanoate
                                                                            C2H5OH, CH3COONa
Aldehydes          Hydrogen                            ethanal              Cyanohydrin RCH(OH)CN          Nucleophilic
RCHO or ketones    cyanide(HCN(covalent)) and          CH3CHO               or RR1C(OH)CN                  substitution
RCOR1              potassium cyanide                   or                   CH3CH(OH)(CN)
                                                       propanone            or
                                                       (CH3)2CO             CH3C(OH)(CH3)CN
                   2, 4-dinitrophenylhydrazine         Dilute sulphuric     2, 4-dinitrophenylhydrazine    Nucleophilic
                   Test for carbonyl(C=O) group        acid                 (Orange ppt)                   substitution
                                                                                                           followed by
                                                                                                           elimination
                   Sodium borohydride NaBH4 or         ethanal              Primary alcohol RCH2OH or      Reduction
                   lithium aluminium hydride           CH3CHO               secondary alcohol
                   LiAlH4                                                   RCH(OH)R1
                                                       or                   Primary alcohol, ethanol
                                                       propanone            C2H5OH
                                                       (CH3)2CO             or
                                                                            Secondary alcohol propan-2-
                                                                            ol
                                                                            CH3CH(OH)CH3
Aldehydes          Ammonical silver nitrate solution   Warm in water bath   Silver mirror                  Reduction of the
RCHO (not          (Tollens reagent)                   ethanal              Carboxylic acid                silver ion
ketones)                                               CH3CHO               ethanoic acid
Test for CHO                                                                CH3COOH
group             Fehling’s solution/Benedicts                             Copper(I) oxide ppt (Red)      Reduction of the
                   solution(Blue)                                                                          copper(II) ion
                   potassium                                                (green)
                   dichromate(VI)(orange)
Aldehydes          acidic conditions                                        Carboxylic acid RCOOH          Oxidation
RCHO             alkaline conditions                                     salt RCOO-X
Carbonyl         NaOH + I2                       Heat                    RCOONa + CHI3             Haloform
compounds                                                                (iodoform/yellow ppt)
containing
CH3C=O and
alcohols
containing
CH3CH(OH)
Acid chlorides   Water                           ethanoyl chloride       Carboxylic acid           Nucleophilic
ROCl                                             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
                 phenylamine                                             R1CONHR
                 C6H5NH2                                                 CH3CONHC6H5
Amines RNH2      Aqueous acid                    ethylamine              salt RNH3+Cl-             Acid-base
                 HCl(aq)                         C2H5NH2                 C2H5NH3+Cl-
                 Acid chloride R1OCl                                     N-substituted amide       Nucleophilic
                 ethanoyl chloride                                       R1CONHR                   substitution
                 CH3COCl                                                 CH3CONHC2H5
Amides RCONH2    Phosphorus(V) oxide P4O10       ethanamide              Nitrile RCN               Dehydration
                                                 CH3CONH2                ethanonitrile
                                                                         CH3CN
                 Bromine followed by NaOH(aq)                            Amine RNH2                Substitution
                                                                         methylamine               followed by
                                                                         CH3NH2                    rearrangement
                                                                                                   and 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       Dry ether               Amine RCH2NH2             Reduction
                 LiAlH4                          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)         halogenoarene
benzene C6H6     Br2                               Anhydrous AlCl3        bromobenzene
                                                                          C6H5Br(l) + HBr(g)
arene            Chloroalkane                      Catalyst (dry)         ethylbenzene
benzene C6H6     Chloroethane    C2H5Cl            Anhydrous AlCl3        C6H5C2H5(l) + HCl(g)
arene            Acid chloride                     Catalyst (dry)         Ketone
benzene C6H6     Ethanoyl chloride CH3COCl         Anhydrous AlCl3        phenylethanone
                                                                          C6H5COCH3(l) + HCl(g)
arene            Potassium manganate VII           alkaline               Carboxylic acid
methylbenzene    KMnO4                             conditions             benzoic acid
C6H5CH3                                            heat under reflux      C6H5COOH + H2O
Aromatic nitro   C6H5NO2 + 6H+ + 6e- C6 H5NH2     heated under reflux    Amines
compounds        + 2H2O                            with tin in conc.
                 nitrobenzene                      HCl as reducing
                 aminobenzene                      agent
                                 (phenylamine)
Phenol           Sodium hydroxide                                         Sodium phenoxide
C6H5OH               NaOH                                                            C6H5O-Na+(aq) + H2O(l)
Phenol               Bromine                                                         C6H2Br3OH(aq) +              substitution
C6H5OH               Br2                                                             3HBr(aq)
                                                                                     2,4,6-tribromophenol
                                                                                     (TCP)
Phenol                 ethanoyl chloride                     Dry                     ester
C6H5OH                 CH3COC                                                        CH3COOC6H5 + HCl
                                                                                     phenylethanoate
Phenylamine            nitrous acid                          5oC                     C6H5NH2 + HNO2 + HCl
C6H5NH2                HNO2                                  NaNO2 and dil            2H2O + C6H5N2+Cl-
                                                             HCl situ                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




 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 red
 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
                                                     Boiling under reflux is necessary when either the reactant has a         Solid can be iden
                                                     low Bt or the reaction is slow at RT                                     Solid must be pur
                                                     - condenses vapours and returns reagents to flask, prevents loss of      Impurities lower t
                                                     reactants/products, prolonged heating for slow reactions                 Thermometer doe
                                                     - For preparation of aldehyde/carboxylic acid from alcohol
                                                                                                                              Recrystallisation
                                                     (1)Reason for heating the mixture but then taking the flame away         Dissolve the solid
                                                     (1)provide Ea, exothermic/prevent reaction getting out of control        Filter the hot solu
                                                                                                                              paper.
                                                                                                                              Allow to cool.
                                                                                                                              Filter under reduc
                                                                                                                              Wash with a little




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

(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


                                     Phenylethanoic acid can be synthesised from benzene as follows:
(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.




(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.




                                              X is                          OR

(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:
            Suggest with a reason the structure of Y.




                                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




           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.




(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




(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, CH 2=C(CH3)COOCH3, is
prepared industrially from propanone




                                                                                (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.




                                                                           OR




(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.
(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).




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




(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)
(a) (i) State the catalyst that is needed for Step 1                                                                  aluminium
chloride/AlCl /Al Cl / iron(III) chloride/FeCl
                3     2   6                      3


(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.
                                                                                             +         2-
 First step        Potassium dichromate +sulphuric acid   OR acidified dichromate     OR H + Cr O            OR (potassium)
                                                                                                  2   7
manganate(VII)/permanganate + acid/alkali/neutral
 heat / reflux
 Intermediate: CH COOH/CH CO H
                          3           3   2
 Second step          PCl / PCI / SOCl
                              5   3       2


(b) Give the reagents and conditions needed for, step 2 & 3                             Step 2    LiAlH               dry ether /
                                                                                                              4
ethoxyethane (followed by hydrolysis)
                                                                                        OR        NaBH                aqueous
                                                                                                              4
ethanol/water
                                                                                        OR        Na                  ethanol
                                                                                        OR        H                   Pt OR
                                                                                                          2
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.
(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
                                        –1
shows bond due to OH at 3230-3550cm
                                              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/I /sodium iodate(I) / NaOI /NaIO/iodate(I)/ OI /IO
                 2


(ii) Give the equation for the reaction of A with iodine in sodium hydroxide.
                          –              –             –
C H COCH + 3I + 4OH C H COO + CHI + 3I + 3H O                                  OR      C H COCH + 3I + 4NaOH 
 6   5      3    2              6   5            3           2                            6   5     3     2
C H COONa + CHI + 3NaI + 3H O
 6   5               3              2
(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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