Polymerisation ofalkenesMANY MONOMERS SINGLE POLYMER→The monomer used isan unsaturated alkenecontaining a doubleC=C bond.The addition polymer formed isa saturated compound without adouble bond.Addition ReactionE.GRepeating unit
Examples and uses ofPoly(alkenes)C CHHH HHHHHnC CnH HHH HHCH3CH3C CnC CnE.G.Ethene poly(ethene)Polyethene is most widely used in plastic shopping bags.Used to also make bottles, cling film &cable insulationE.G.Propene poly(propene)Polypropene is used in biros, straws, chairs, bucketsand plastic food containers.It can be recycled commercially.
RecyclingPolymersLots of crude oil is used to make polymers =waste to throw awayPoly(propene) > recycled via feedstock recycling = decomposing at high temps to produce napthaReuse Polymerse.g. making more durableplastic bags that can be usedagainReprocessing scraps frommanufacturing processesSo can melt and re-use formanufacturing processesIncineration. Burningpolymers release thermalenergy for generatingelectricity.But releases co2 socontributes to globalwarming
EthanolProductionfermentation ofsugarsC6H12O6 2C2H5OH + 2CO2Optimum temp = 36degrees(High temps denatureenzyme and kills yeast)Advantages:•it is a relatively fast process•it is a continuous flow process,which means that ethene can beentered into the vesselcontinuously and the reactionnever has to be stopped•it produces pure ethanolDisadvantages:•it requires fairly high technology•it uses a lot of energy•the ethene comes from crude oil,which is a non-renewable resource
Ethanol as abiofuelEthanol is a useful fuel; it burns with a clean flame andis increasingly used in cars:C2H6O(l) + 3O2(g) 3CO2(g) + 3H2O(g)• Ethanol produced by fermentation = renewable fuel• Biofuels are carbon-neutral= there are no net annual carbon (greenhouse gas)emissions to the atmosphere
secondary andtertiaryalcoholsPrimary alcohols are those in which the carbon attached to the OH is attached to 0 or 1other carbon atom.Eg propan-1-olC C CHHH HHHOHH
secondary andtertiaryalcoholsSecondary alcohols are those in which the carbon attached to the OH is attached to 2other carbon atoms. In other words, they are molecules in which the functional group isnot at the end of the chain.Eg propan-2-olH CHHCHCHHHOHH CHHCHCHHHOH
secondary andtertiaryalcoholsTertiary alcohols are those in which the carbon atom attached to the OH is attached to 3other carbon atoms. In other words, they are molecules in which the functional group isattached to a carbon which also has a branch attached to it.Eg 2-methypropan-2-olH CHHCHCHHOHH HCH
H HHHCC OHH+ [O]+ H2OCOHHHCHCOHCOCH3CH3CHOHCH3CH3+ [O] + H2OCOIf a primary alcohol is mixed with an oxidising agent, two hydrogen atoms can be removed and an aldehyde will be formed:Eg CH3CH2OH + [O] CH3CHO + H2OEthanol EthanalAn aldehyde is a molecule containing the following group:If a secondary alcohol is mixed with an oxidising agent, two hydrogen atoms can be removed and a ketone will be formed:Eg CH3CH(OH)CH3 + [O] CH3COCH3 + H2OPropan-2-ol propanoneA ketone is a molecule containing the following group:mild oxidation of primary andsecondary alcohols
Tertiary alcohols are not readily oxidised since they do not have available H atoms to give up.Aldehydes and ketones are collectively known as carbonyls and can be represented by the general formula CnH2nOCORRIn aldehydes, one of the R groups is a H atom. In ketones, neither of the R groups is a H atom.Further oxidation of aldehydesIf an aldehyde is mixed with an oxidising agent, an oxygen atom can be added to the group and a carboxylicacid will be formed:Eg CH3CHO + [O] CH3COOHEthanal Ethanoic acidA carboxylic acid is a molecule containing the following group:Ketones cannot be oxidised into carboxylic acids since there is no C-H bond into which an oxygenatom can be inserted.
Summary of oxidationreactions of alcoholsand carbonylsprimaryalcoholssecondaryalcoholstertiaryalcoholsaldehydes ketonescarboxylicacidsX[O][O][O]
Tests to distinguishbetween aldehydesand ketones• Tollen’s reagent- Tollen’s reagent, is anoxidising agent and willreact with aldehydes onboiling:o In the presence ofaldehydes, the colourlessAg+ ions (Tollen’s reagent)in are reduced tometallic silver, whichforms on the surface ofthe test tube• Fehling’s solution- Fehling’s solution contains Cu2+ ions.- Aldehydes are reducing agents butketones are not.- Cu2+ is an oxidising agent and will reactwith aldehydes on heating.o In the presence of aldehydes,the blue Cu2+ is reduced to thered copper (I) oxide, Cu2O.The presence of a brick redprecipitate of Cu2O indicates thatan aldehyde is present.