Topic 5.5 Organic chemistry analysis, synthesis and application

(a) Organic analysis(i) Functional groups

Task 5.5a.1 Complete a copy of the table below with names and structural formulae:

Task 5.5a.2 Write an equation for each of the reactions above.
Task 5.5a.3 Predict the result of carrying out an iodoform test on the following compounds: methanol, ethanol, propan-1-ol, methanal, ethanal, propanone.

(ii) Interpretation of physical data

* A pure solid can be identified by its melting temperature, a pure liquid by its boiling temperature. Aldehydes and ketones produce solid derivatives with 2,4-dinitrophenylhydrazine (hydrazones) which have high melting points. The melting points of these derivatives can be used to identify the original ketone or aldehyde.

substance	boiling point/oC	melting point of hydrazone/oC
propanal	48	156
pentan-2-one	102	141
pentan-3-one	102	156

What are the identities of the following:
Compound A forms a yellow precipitate with  2,4-dinitrophenylhydrazine and an orange precipitate with Fehlings solution. When the yellow precipitate is purified it melts at 156^oC.
Compound B forms a yellow precipitate with  2,4-dinitrophenylhydrazine but does not form a silver mirror with Tollens reagent. When the yellow precipitate is purified it melts at 156^oC.

The percentage by mass of Carbon and Hydrogen in a hydrocarbon can be found by the following method; 
A known mass of the compound heated in a stream of pure, dry oxygen in the presence of copper (II) oxide when hydrogen and carbon are oxidised, to steam and carbon dioxide respectively.  The steam absorbed in weighed calcium chloride tubes, and carbon dioxide absorbed in weighed bulbs of concentrated potassium hydroxide solution.  The masses of carbon and hydrogen in the sample are found from the increases in mass.

Draw suitable labelled apparatus for the above procedure.
If 7.80g of a hydrocarbon causes calcium chloride to increase in mass by 5.40g and potassium hydroxide to increase in mass by 26.4g what was the formula of the hydrocarbon?

5.5a(iii)(a) interpret simple fragmentation patterns from a mass spectrometer
An organic compound produces ions in a mass spectrometer.  The ions generate pulses of electric current which are sent as signals to a computer (or chart plotter) to be displayed as a mass spectrum.  On the spectrum the large peak on the right is the parent molecular ion and this indicates the relative molecular mass of the compound.  In the spectrometer the molecules are fragmented into positive ions which form a pattern which depends on the structure of the molecule. e.g.  ether

Another compound of relative molecular mass 46 also contains carbon, hydrogen and oxygen has the mass spectrum below.  Identify each fragment and the structural formula.

Sketch the mass spectrum of propanal showing the masses of each fragment.
Task 5.5a(iii)a

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.  These might be stretching, or bending vibrations.  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.

Infra-red spectrum for propanone

Is substance A in the infra-red spectrum below most likely to be ethyl ethanoate or butane?
Task 5.5aiiib

5.5a(iii)(c) Low resolution nuclear magnetic resonance spectra (NMR)
Hydrogen atoms can be detected using this sort of spectrometry.  The nucleus of a hydrogen atom, the proton, spins and so has a magnetic moment.  This can be aligned or not aligned with a magnetic field .  When electromagnetic radiation of the right frequency is applied resonance occurs and the protons flip from one state to the other and absorb energy.  This absorption of energy is used to detect protons in organic compounds.   The exact resonance frequency for a proton (hydrogen atom) depends on its environment.  For example the frequency is different for hydrogen atoms in CH₃, CH₂ , C₆H₅- and in O-H.  Trimethylsilane,  TMS, is used as a standard.  The distance in the spectrum from the TMS peak is called the chemical shift.

To which functional groups do the protons in the following NMR spectrum belong?  Identify the compound.

Sketch an NMR spectrum for propanal.

An excellent guide to low resolution nmr.

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.  b-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

 Alkanes

Organic reactant	Reagent	Conditions	Organic Products
Alkane  ethane  C2H6	halogen  bromine  Br2	UV light inert solvent	halogenoalkane  bromoethane  CH3CH2Br
Alkane  ethane  C2H6	halogen  chlorine  Cl2	UV light inert solvent	halogenoalkane  chloroethane  CH3CH2Cl

Alkenes

Organic reactant	Reagent	Conditions	Organic Products
Alkene  ethene  C2H4	halogen  bromine  Br2	inert solvent	halogenoalkane  1,2-dibromoethane  CH2BrCH2Br
unsymmetric alkene  prop-1-ene  CH3CHCH2	hydrogen halide  hydrogen bromide  HBr	inert solvent	halogenoalkane  2-bromopropane  CH3CHBrCH3
Alkene  ethene  C2H4	potassium manganate(VII)  KMnO4	alkaline solution	ethane-1,2-diol  CH2OHCH2OH

Arenes

Organic reactant	Reagent	Conditions	Organic Products
arene  benzene  C6H6	nitric acid  sulphuric acid	heat under reflux  below 60oC  concentrated acids	nitrobenzene  C6H5NO2
arene  methylbenzene  C6H5CH3	potassium manganate VII	alkaline conditions  heat under reflux	benzoic acid  C6H5COOH
arene  benzene  C6H6	chloroalkane  chloromethane  CH3Cl	anhydrous aluminium chloride as catalyst	arene  methylbenzene  C6H5CH3
arene  benzene  C6H6	acid chloride  ethanoyl chloride  CH3COCl	anhydrous aluminium chloride as catalyst	ketone  methylphenylketone  C6H5COCH3
arene  benzene  C6H6	halogen bromine Br2	anhydrous aluminium chloride as catalyst	halogenoarene bromobenzene C6H5Br
diazonium salt  benzen diazonium chloride C6H5N2+Cl-	phenol  C6H5OH	below 5oC	azo dye  C6H5N2C6H5OH
diazonium salt  benzene diazonium chloride C6H5N2+Cl-	2-naphthol	below 5oC	azo dye  C10H6(OH)N2C6H5
phenylamine  C6H5NH2	nitrous acid  HNO2	below 5oC  NaNO2 and dil HCl	diazonium salt  benzenediazonium chloride C6H5N2+Cl-
nitrobenzene  C6H6NO2	concentrated hydrochloric acid and tin HCl and Sn	heat under reflux	phenylamine  C6H5NH2
phenol C6H5OH	sodium hydroxide	aqueous	sodium phenoxide C6H5ONa
phenol C6H5OH	bromine	aqueous	2,4,6-tribromophenol C6H2Br3OH
phenol C6H5OH	ethanoyl chloride		ester ethylbenzoate C6H5COOC2H5

Primary alcohols

Organic reactant	Reagent	Conditions	Organic Products
primary alcohol  ethanol  C2H5OH	aqueous potassium dichromate VI  dilute sulphuric acid	distil product mild conditions	aldehyde  ethanal  CH3CHO
primary alcohol  ethanol  C2H5OH	aqueous potassium dichromate VI  dilute sulphuric acid	boil under reflux forcing conditions	carboxylic acid  ethanoic acid  CH3COOH
primary alcohol  ethanol  C2H5OH	hydrogen halide  hydrogen bromide  HBr	heat under reflux HBr formed in situ from KBr and conc. H2SO4	halogenoalkane  bromoethane  C2H5Br
primary alcohol  ethanol  C2H5OH	phosphorus and iodine	red phosphorus	halogenoalkane iodoethane C2H5I
primary alcohol  ethanol  C2H5OH	carboxylic acid  ethanoic acid  CH3COOH	concentrated H2SO4	ester  ethyl ethanoate  CH3COOC2H5
primary alcohol  ethanol  C2H5OH	acid chloride  ethanoyl chloride  CH3COCl	.	ester  ethyl ethanoate  CH3COOC2H5
primary alcohol  ethanol  C2H5OH	phosporus pentachloride	.dry	halogenoalkane  chloroethane  C2H5Cl

Secondary alcohols

Organic reactant	Reagent	Conditions	Organic Products
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	aqueous potassium dichromate VI  sulphuric acid	conc. acid  heat under reflux	ketone  propanone  CH3COCH3
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	hydrogen halide  hydrogen bromide  HBr	heat under reflux HBr formed in situ from KBr and conc. H2SO4	halogenoalkane  2-bromopropane  CH3CH2(Br)CH3
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	carboxylic acid  ethanoic acid  CH3COOH	concentrated H2SO4	ester  2-propylethanoate  CH3COOCH(CH3)2
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	acid chloride  ethanoyl chloride  CH3COCl	.	ester  2-propylethanoate  CH3COOCH(CH3)2
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	phosphorus and iodine	red phosphorus	halogenoalkane 2-iodopropropane CH3CH(I)CH3
secondary alcohol  propan-2-ol  CH3CH(OH)CH3	phosporus pentachloride	dry	halogenoalkane  2-chloropropane  CH3CH2(Cl)CH3

Tertiary alcohols

Organic reactant	Reagent	Conditions	Organic Products
tertiary alcohol  2-methylpropan-2-ol  (CH3)3OH	hydrogen halide  hydrogen bromide  HBr	heat under reflux HBr formed in situ from KBr and conc. H2SO4	halogenoalkane  2-bromo-2-methylpropane  (CH3)3Br
tertiary alcohol  2-methylpropan-2-ol  (CH3)3COH	carboxylic acid  ethanoic acid  CH3COOH	heat  concentrated H2SO4	ester  CH3COOC(CH3)3
tertiary alcohol  2-methylpropan-2-ol  (CH3)3OH	acid chloride  ethanoyl chloride  CH3COCl	.	ester  CH3COOC(CH3)3
tertiary alcohol  2-methylpropan-2-ol  (CH3)3OH	phosphorus and iodine	red phosphorus	halogenoalkane 2-iodo-2-methylpropropane (CH3)3I
tertiary alcohol  2-methylpropan-2-ol  (CH3)3OH	phosporus pentachloride	dry	halogenoalkane (CH3)3Cl

Carboxylic acids

Organic reactant	Reagent	Conditions	Organic Products
carboxylic acid  ethanoic acid  CH3COOH	alcohol  ethanol  C2H5OH	heat  concentrated H2SO4	ester  ethyl ethanoate  CH3COOC2H5
carboxylic acid  ethanoic acid  CH3COOH	lithium aluminium hydride	dissolved in dry ether	alcohol  ethanol  C2H5OH
carboxylic acid  ethanoic acid  CH3COOH	phosphorus pentachloride	dry	acid chloride  ethanoyl chloride  CH3COCl
carboxylic acid  ethanoic acid  CH3COOH	sodium carbonate or  sodium hydrogencarbonate		salt sodium ethanoate CH3COONa

Primary amines

Organic reactant	Reagent	Conditions	Organic Products
primary amine  ethylamine  C2H5NH2	acid  hydrochloric acid  HCl	aqueous solution	salt  alkyl ammonium chloride  C2H5NH3+Cl-
primary amine  ethylamine  C2H5NH2	acid chloride ethanoyl chloride CH3COCl		amide N-ethylethanamide  CH3CONHC2H5

Halogenoalkanes

Organic reactant	Reagent	Conditions	Organic Products
halogenoalkane  bromoethane  C2H5Br	hydroxide ion  sodium hydroxide  NaOH	aqueous solution	alcohol  ethanol  C2H5OH
halogenoalkane  bromoethane  C2H5Br	hydroxide ion  potassium hydroxide  KOH	heat and distil off product  ethanolic solution	alkene  ethene  C2H4
halogenoalkane  bromoethane  C2H5Br	cyanide ion  potassium cyanide  KCN	heat under reflux in ethanolic solution	nitrile  propanonitrile  C2H5CN
halogenoalkane  bromoethane  C2H5Br	ammonia	heat with concentrated ammonia in a sealed tube	amine  ethylamine etc  C2H5NH 2 ;  (C2H5)2NH etc
halogenoalkane  bromoethane  C2H5Br	magnesium  Mg	in solution in dry ether	grignard reagent  ethylmagnesiumbromide  C2H5MgBr

Grignard reagent

Organic reactant	Reagent	Conditions	Organic Products
grignard reagent  ethylmagnesiumbromide  C2H5MgBr	methanal  HCHO	in ether solution followed by dilute acid	primary alcohol  propan-1-ol  C2H5CH2OH
grignard reagent  ethylmagnesiumbromide  C2H5MgBr	aldehyde  ethanal  CH3CHO	in ether solution followed by dilute acid	secondary alcohol  butan-2-ol  CH3CH2CH(OH)CH3
grignard reagent  ethylmagnesiumbromide  C2H5MgBr	ketone  propan-2-one  (CH3)2CO	in ether solution followed by dilute acid	tertiary alcohol  2-methylpropan-2-ol  (CH3)3OH
grignard reagent  ethylmagnesiumbromide  C2H5MgBr	carbon dioxide  CO2	in ether solution followed by dilute acid	carboxylic acid  propanoic acid  C2H5COOH

Ketones

Organic reactant	Reagent	Conditions	Organic Products
ketone  propanone  (CH3)2CO	hydrogen cyanide	in alkaline conditions  potassium cyanide used as source of HCN	alcohol, nitrile 2-hydroxy -2-methylpropanonitrile  CH3C(OH)(CH3)CN
ketone  propanone  (CH3)2CO	2,4-  dinitrophenylhydrazine  C6H3(NO2)2NHNH2	dil. sulphuric acid	2,4-  dinitrophenyhydrozone  C6H3(NO2)2NHNC(CH3)2
ketone  propanone  (CH3)2CO	iodine or sodium iodide and chloate(I)	alkaline conditions	halogenoalkane tri-chloromethane  (iodoform)
ketone  propanone  (CH3)2CO	sodium borohydride  NaBH4	aqueous solution	secondary alcohol  propan-2-ol  CH3CH(OH)CH3
ketone  propanone  (CH3)2CO	Lithium aluminium hydride  LiAlH4	dry ether solution	secondary alcohol  propan-2-ol  CH3CH(OH)CH3

Aldehydes

Organic reactant	Reagent	Conditions	Organic Products
aldehyde  ethanal  CH3CHO	hydrogen cyanide	in alkaline conditions  potassium cyanide used as source of HCN	alcohol, nitrile 2-hydroxypropanonitrile  CH3CH(OH)(CN)
aldehyde  ethanal  CH3CHO	2,4-  dinitrophenylhydrazine  C6H3(NO2)2NHNH2	dilute sulphuric acid	2,4-  dinitrophenyhydrozone  C6H3(NO2)2NHNCHCH3
aldehyde  ethanal  CH3CHO	ammoniacal silver nitrate solution  (Tollen's reagent)	warm in water bath	carboxylic acid  ethanoic acid  CH3COOH
aldehyde  ethanal  CH3CHO	iodine or sodium iodide and chlorate(I)	alkaline conditions	halogenoalkane tri-chloromethane  (iodoform)
aldehyde  ethanal  CH3CHO	sodium borohydride  NaBH4	aqueous solution	alcohol  ethanol  C2H5OH
aldehyde  ethanal  CH3CHO	Lithium aluminium hydride  LiAlH4	dry ether solution	alcohol  ethanol  C2H5OH

Acid chlorides

Organic reactant	Reagent	Conditions	Organic Products
acid chloride  ethanoyl chloride  CH3COCl	water  H2O	.	carboxylic acid  ethanoic acid  CH3COOH
acid chloride  ethanoyl chloride  CH3COCl	alcohol ethanol CH3CH2OH	no water	ester  ethyl ethanoate  CH3COOC2H5
acid chloride  ethanoyl chloride  CH3COCl	ammonia  NH3	conc. ammonia	amide  ethanamide  CH3CONH2
acid chloride  ethanoyl chloride  CH3COCl	primary amine  phenylamine  C6H5NH2	.	amide N-phenylethanamide  CH3CONHC6H5

Nitriles

Organic reactant	Reagent	Conditions	Organic Products
nitrile  ethanonitrile  CH3CN	water	acidic heat under reflux	carboxylic acid  ethanoic acid  CH3COOH
nitrile  ethanonitrile  CH3CN	water	alkaline heat under reflux	salt  sodium ethanoate  CH3COONa
nitrile  ethanonitrile  CH3CN	lithium aluminium hydride	dry ether solution	amine  ethylamine  CH3CH2NH2

Amides

Organic reactant	Reagent	Conditions	Organic Products
amide  ethanamide  CH3CONH2	phosphorus V oxide	.	nitrile  ethanonitrile  CH3CN
amide  ethanamide  CH3CONH2	bromine	aqueous alkali	amine  methylamine  CH3NH2

Esters

Organic reactant	Reagent	Conditions	Organic Products
ester  ethyl ethanoate  CH3COOC2H5	water	conc. sulphuric acid	alcohol, acid ethanol, ethanoic acid  C2H5OH, CH3COOH
ester  ethyl ethanoate  CH3COOC2H5	water	aqueous sodium hydroxide	alcohol ethanol, sodium ethanoate C2H5OH, CH3COONa

5.5b (ii) Apparatus and safety in organic synthesis
Organic compounds may be hazardous because of:
    Flammability.
Use in small amounts avoids the undue risk of fire.  Avoid naked flames.  Use electrical heaters
    Toxicity
The use of small amounts, fume cupboards, gloves and normal laboratory safety procedures  reduces the risk of harmful amounts of a chemical entering the body by inhalation, ingestion or by skin absorption.
    Non-biodegradability
Some substances do not decay naturally in the environment.  The hazard is reduced by using small quantities, and pouring waste solvents in a suitable container rather than pouring it down the sink.
When carrying out organic reactions safety goggles should always be worn.
Some common apparatus for organic preparation: Quickfit apparatus such as a

pear shaped flask


Liebig condenser   T connector                                  thermometer holder
      
Separating funnel   delivery tubes                            
         

5.5b (iii) Practical techniques
Mixing can involve adding a liquid to a solid or another liquid using a separating funnel.
Mixing can involve adding a gas to a liquid through a delivery tube into the liquid.

boiling under reflux, 
Practice setting up reflux apparatus.  (Needs Microsoft Word.)
         
fractional distillation, 

Filtration under reduced pressure (filter pump and Buchner funnel an flask), 
 
Recrystallisation
This is used to purify an impure organic solid.
1. Choose a suitable solvent.  The solvent is suitable if the product is insoluble in the cold solvent but soluble in the hot solvent.
2. Dissolve the impure sample in the minimum volume of hot solvent.
3. Filter the hot solution through hot apparatus and collect the filtrate.  This removes solid impurities which were insoluble in the solvent.
4. Allow the filtrate to cool so that crystals of the product form.
5. Again filter the mixture under reduced pressure.  Soluble impurities are now removed.
6. Wash the residue with a little cold solvent.
7. Dry the residue which should then be the pure product.

Describe with a series of labelled diagrams how compound X can be purified using the information below.

Determination of melting temperature
A pure solid has a sharp melting point which can be found in a data book.  If a solid product has been purified it can be identified from its melting point or if we know what it is we can tell if it is pure.  Impurities lower the melting point.

 
1. A liquid is chosen for the boiling tube so that its boiling point is well above the melting point of the solid.
2. The apparatus is set up as shown.
3. The apparatus is heated gently with stirring until the first solid is seen to melt when the temperature is recorded.
4. After the sample is melted it is allowed to cool.
5. When the first crystals of solid appear in the sample the temperature is recorded again.

Comment on the purification of X by student A and B given the data below.

Determination of boiling temperature
   In both apparatus the bulb of the thermometer is below the surface of the liquid but not touching the side of the glass.
Heating with a variety of sources
Heating with a naked Bunsen flame is a fire hazard with flammable organic compounds.  Alternatives include using an electrically heated hot plate, using an electrical heating mantle which can surround a round bottom flask or using a water bath.
Other apparatus

5.5b(iv) The principles of fractional distillation

Raoult's Law

Raoult's law states that the saturated vapour pressure of a component in a mixture is equal to the product of the mole fraction of that component and the saturated vapour pressure of that component when pure.

For a mixture of A and B obeying Raoult's law pA = p^oA * XA

where pA = partial vapour pressure of A in the solution

p^oA = vapour pressure of pure A

XA = mole fraction of A in the solution

mole fraction of A in mixture A+B, XA = nA/nA+nB

nA= no. moles A

nB= no. moles B.

pT = p^oA * XA + p^oB * XB

where pT = total vapour pressure

This law is obeyed by mixtures of similar compounds. They form IDEAL SOLUTIONS. The substances A and B form an ideal solution if the intermolecular forces A----A, A----B, B----B are all equal. As these forces are alike the vapour pressure of an ideal mixture is not increased or decreased because the escape of molecules is neither helped nor hindered. Also for an ideal solution there is:

(1) no enthalpy change on mixing;

(2) no volume change on mixing.

Diagrams for Idea Solutions

Task 5.5biv.1 Pure hexane has a vapour pressure of about 340 mmHg and pure pentane has a vapour pressure of about 310 mmHg.  Sketch a vapour pressure composition graph and a boiling point composition graph for a mixture of these two compounds.

Fractional distillation

This technique has a number of important applications:

(1) used to separate the components of liquid air; The air is compressed and cooled to liquefy it. Fractions are oxygen -183^oC, argon -186^oC, and nitrogen -196^oC.

(2) used to separate fractions from petroleum; The fractions are bitumen >350^oC, fuel oil 300 ^oC, diesel 240 ^oC, kerosene 200 ^oC, naptha 120 ^oC, petrol 40 ^oC, LPG <25 ^oC.

(3) used to produce whisky and other alcoholic drinks. Fractions are ethanol 78 ^oC and water 100 ^oC.

Principles of fractional distillation

Fractional distillation relies on the fact that the composition of a two liquid mixture in equilibrium with its vapour is different in the liquid and vapour phases. Real mixtures are not ideal and show deviations from Raoult's law.

The particles of one liquid surround those of the other and change the forces on them so affecting their tendency to escape from the liquid.

(1) Negative from deviations Raoult's law:

If the attractive forces between the different particles from the two liquids are stronger than the attractive forces in pure liquids, then the particles will be held in the liquid more strongly. Therefore fewer particles will escape, thus the vapour pressure will be lower than predicted by Raoult's law. Boiling points for any composition of this mixture will be higher than predicted.

(2) Positive deviations from Raoult's law:

If the attractive forces between the different particles from the two liquids are weaker than the attractive forces in the pure liquids, then the particles will be held in the liquid less well. Therefore more particles will escape, thus the vapour pressure will be higher than predicted by Raoult's law. Boiling points for any composition of this mixture will be lower than predicted.

A plot of temperature against composition is needed to explain how fractional distillation works.

For a liquid mixture of composition C1 it will boil at temperature T. It will be in equilibrium with vapour at composition C2. Vapour C2 will condense and then boil to give a mixture richer again in B. Eventually the distillate will be pure B. The residue in the flask will be A.
Task 5.5b(iv).2 Methanol has a boiling point of 338K and ethanol has a boiling point of 351K.  Sketch a temperature composition curve for this mixture and use it to explain how they can be separated.  State the names of the distillate and the residue.

5.5c(i) The solubility of pharmaceuticals

Drugs can be made to target fatty tissue like lipids in the body.  These chemicals will have a large number of CH₃ or CH₂ groups.  The following pharmaceutical inhibits cholesterol synthesis and acts within fatty tissue.

Other pharmaceuticals like penicillin are targeted at non-fatty tissue and must be more water soluble.  For this the molecules must contain hydroxyl groups to form hydrogen bonds to water or an ionic group.  Penicillin-G shown below prevents the growth of cell walls in bacteria and so is an antibiotic.  One draw back is that it is very soluble (due to its ionic group) and is eliminated very rapidly by the kidneys so has to be given in large doses.

Task  5.5c(i).1 Describe the inplications for solubility of ziagen, Aczone Gel
 and other drugs found at
http://www.rxlist.com/drugs/alpha_a.htm

5.5c(ii) The use of organic fertilisers
Inorganic fertilizers like ammonium nitrate and ammonium sulphate are very soluble, can be leached easily which may lead to the eutrophication of rivers and lakes.  Other problems are that they decrease soil pH, and for osmotic reasons, cause burning and foliage decay in some plants.
Urea is an organic fertilizer which only slowly releases nitrogen to the soil, has a high proportion of nitrogen and does not immediately change soil pH.  It undergoes hydrolysis in the soil to form ammonia.
H₂N-CO-NH₂ + H₂O -----> CO₂ +2NH₃
The process is catalysed by urease made by soil bacteria.  The ammonia is converted to nitrates in the soil which can then be absorbed by plants.  Alternatives include manure, hoof and horn, or dried blood.
Task 5.5c(ii).1 State steps in the process of eutrophication.
Task 5.5c(ii).2 Explain equilibrium giving low pH.
Task 5.5c(ii).3 Explain water loss to soil through osmosis.

5.5c(iii) Uses of esters, oils and fats
Esters find a use as food flavourings because of their characteristic fruity smells.  Ethyl methanoate is used in raspberry essence.  3-methylbutylethanoate is used in pear essence.
Margarine is made from an ester of a long chain carboxylic acid containing carbon to carbon double bonds.  This unsaturation makes the original ester a liquid oil.  A typical source is peanuts or sunflower seeds.  The amount of unsaturation is reduced in an addition reaction with hydrogen using a nickel catalyst.  The resulting edible solid fat is margarine.  The nature of fats and oils and saturation.  (requires Powerpoint)
Essential oils are so called because they are extracted from the essence of plants.  The bark of Birch trees can be used to make oil of wintergreen, of use in relief of muscle pain.  This is methyl-2-hydroxylbenzoate.  Many of these essential oils are hydrocarbons or simple derivatives.  Limonene can be separated from citrus peel.  It is a methyl cyclohexene with a CH₃CCH₂ group attached.
The chemistry involved in the production of soaps and soapless detergents
Detergent- A substance that acts as a cleaning agent, improving the ability of water to wash things.

Why is a detergent necessary?
Though very effective at removing water-soluble dirt (hydrophilic), water is poor at removing material that does not dissolve in water (hydrophobic). The main problem is caused by greasy fats and carboxylic acids, which tend to bind other “dirt” particles to the skin or fabric. This prevents them being washed away by water. A detergent works by enabling water to mix with and remove greasy materials.

Types of detergents
(i) Soapy detergents (ii) Soapless detergents
All detergents form a lather easily when shaken with PURE water. But the soapy detergent forms a lather with greater difficulty with tap water (tap water 300 mg/litre Ca²⁺ ); that is, a lather is only possible if a lot of soap is used, so in effect the soap is wasted in hard water. On the other hand, the soapless detergent forms a lather readily in hard water. These differences can be explained if the chemical nature of these materials is considered.

Soapy detergents
Animal fats are in fact esters made from long chain carboxylic acids and the compound glycerol. The alkaline hydrolysis or saponification (soap making) of animal fats gives glycerol and the sodium or potassium salt of the carboxylic acid. It is the salt which is the soap.
            O
               //
      R-C
               \
                O^-Na⁺ (R is the hydrophobic hydrocarbon chain)
(e.g. toilet soap, gels in shampoos, shaving creams especially K+ salts)

The charged -COO^- group (carboxylate ion) at the end of a soap enables it to dissolve in water. Water molecules attach themselves to this end of the soap molecule via hydrogen bonds and the oil/ grease molecules attach around the alkyl with Van der Waals forces. The forces between water and grease are thus much increased, so that the grease is lifted off the surface in the form of small globules. These can be rinsed away.

Advantages:
Reaction of soap is more favourable with skin- more agreeable than with other detergents.

Disadvantages:
They do not remove some types of dirt well
They do not clean very efficiently in hard water, as they react with calcium and magnesium ions to form insoluble calcium/ magnesium salts - scum.  The scum is insoluble calcium or magnesium salt.
2R-COONa (aq) + Ca²⁺(aq) -----> Ca(R-COO)₂(s) + 2Na⁺(aq)
Made from vegetable/ animal fats - often expensive

Soapless detergents
These are very much synthetic materials, they work in a similar way to soaps but a sulphonate group (-SO₂-O-) or sulphate group (-O-SO₂-O) replace the carboxylate group as the hydrophilic component.  The reaction of oil and concentrated sulphuric acid will produce a soapless detergent.

              O                                       O
               ||                                        ||
       R-O-S-O^-Na⁺      also  R-C₆H₄-S-O^-Na⁺
               ||                                        ||
              O                                       O

(e.g. dishwasher powder, washing powder)
The process of sulphonation gives rise to these detergents.

Advs:
The Ca²⁺/ Mg²⁺ compounds formed with soapless detergents are more soluble in water. Thus there is no wastage in hard water.
Made from the by-products of oil refining, therefore quite cheap to make.

Disadvs:
First soapless detergents were not biodegradable- the side chains cannot be degraded. Thus when discharged in rivers, the microorganisms present in the water can not destroy them. Thus causing foaming in rivers and streams. This has been overcome by modifying the structure of the detergents.  Chains without branches were introduced which are biodegradable.

Task 5.5d(iii) In the following molecules on the web page below explain if they are soapy or soapless, which part of the molecule dissolves in water and which part in oil and state what if anything would happen if calcium ions were present.
http://www.elmhurst.edu/~chm/vchembook/558detergent.html

5.5d(iv) Uses and properties of polymers