Unit 2 The World of Carbon Menu Fuels Nomenclature Reactions of Carbon Compounds Polymers Natural Products.

Unit 2The World of

Carbon

Menu

• Fuels• Nomenclature• Reactions of Carbon Compounds• Polymers• Natural Products

Fuels

Crude oil

• Crude oil is a source of many fuels.

• It is also the principal feedstock for the manufacture of petroleum-based consumer products because these are compounds of carbon.

Petrol

• Petrol can be produced by the reforming of naphtha.

• Reforming alters the arrangement of atoms in molecules without necessarily changing the number of carbon atoms per molecule.

Aromatic hydrocarbonBranched-chainhydrocarbon

Cycloalkane

•As a result of the reforming process, petrol contains branched-chain alkanes, cycloalkanes and aromatic hydrocarbons as well as straight-chain alkanes.

• Any petrol is a blend of hydrocarbons which boil at different temperatures.

• A winter blend of petrol is different from a summer blend. In winter butane is added to petrol so that it will catch fire more easily.

Engines

• In a petrol engine, the petrol-air mixture is ignited by a spark.

• ‘Knocking’ is caused by auto-ignition.

• Auto-ignition is when the petrol-air mix ignites too soon due to the heat from the engine. This makes the engine perform badly.

• Knocking is when the engine shakes and shudders.

• The tendency of alkanes to auto-ignite used to be reduced by the addition of lead compounds.

• Unfortunately the lead compounds cause serious environmental problems.

• Unleaded petrol uses components which have a high degree of molecular branching and/or aromatics and/or cycloalkanes to improve the efficiency of burning.

Alternative fuels

• Fossil fuels are going to run out in the future.

• Fuels used produce carbon dioxide, which increases the “greenhouse effect”.

• We need other fuels which are renewable and non-polluting.

• Sugar cane is a renewable source of ethanol for mixing with petrol.

• Some biological materials,(i.e. manure and straw) under anaerobic conditions, ferment to produce methane (biogas).

• Methanol is an alternative fuel to petrol, but it has certain disadvantages, as well as advantages.

Methanol

• Almost complete combustion

• No carcinogens• Cheaper than

petrol• Less explosive

than petrol• Little

modification to car engine

• Difficult to mix with petrol

• Very corrosive• Toxic• Larger fuel

tanks needed.

• Hydrogen could well be the fuel of the future.

• If water can be electrolysed, using a renewable energy source, such as solar power, hydrogen will be obtained.

• The hydrogen will burn, producing water, and so will be pollution-free.

• The problem with hydrogen is storing the gas in large enough quantities.

Fuels

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Nomenclature &Structural formula

Nomenclature

• Nomenclature means the way chemical compounds are given names.

• These names are produced by a special system.

Naming organic compounds

• All organic compounds belong to “families” called homologous series.

• A homologous series is a set of compounds with the same general formula, similar chemical properties and graded physical properties.

• Most homologous series have a special functional group.

• A functional group is a reactive group of atoms which are attached to the carbon chain.

• The functional group is the part of the molecule where most reactions take place.

Functional Groups

Functional Group

Name of Group

Homologous series

none Alkanes

Double bond

Alkenes

Triple bond Alkynes

Hydroxyl Alkanols (Alcohols)

C C

C C

O H

Functional Groups

Functional Group

Name of Group

Homologous series

Carbonyl Alkanals (Aldehydes)

Carbonyl Alkanones (Ketones)

Carboxylic Alkanoic acids

Amine Amines

C H

O

C

O

C OH

O

NH2

• The first part of the compound’s name is decided by the number of carbon atoms in the molecule.

• The second part of the name is decided by the homologous series to which the compound belongs.

Number of C atoms

First part of name

Number of C atoms

First part of name

1 meth- 5 pent-

2 eth- 6 hex-

3 prop- 7 hept-

4 but- 8 oct-

2nd Part of Name

Homologous series

General Formula

Name ending

Alkanes CnH 2n+2 …ane

Alkenes CnH 2n …ene

Alkynes CnH 2n-2 …yne

Alkanols CnH 2n+1OH …anol

2nd Part of Name

Homologous series

General Formula

Name ending

Alkanals CnH 2n+2 …anal

Alkanones CnH 2n …anone

Alkanoic acids

CnH 2n-2 …anoic acid

Amines CnH 2n+1OH …ylamine

• This method works well for straight-chain hydrocarbons.

• Here is an example: hexane

H H H H H H

H C C C C C C H

H H H H H H

• We have to add rules to help deal with branched chains.

H H H H CH3 H

H C C C C C C H

H H CH3 H CH3 H

• First draw out the full structure.

H H H H CH3 H

H C C C C C C H

H H CH3 H CH3 H

• Number the atoms in the longest continuous carbon chain.

• Start at the end nearer most groups. H H H H CH3 H

H C C C C C C H

H H CH3 H CH3 H

6 5 4 3 2 1

• This now gives us the basic name – in this case hexane.

H H H H CH3 H

H C C C C C C H

H H CH3 H CH3 H

6 5 4 3 2 1

• You must now identify any side chains.

• -CH3 is methyl

• -CH2CH3 is ethyl

• Now identify and count the number and type of side chain.

• di - shows 2• tri – shows 3• tetra – shows 4• Label the carbon atom(s) they

join

• This now gives us the full name:

• 2,2,4 trimethylhexane. H H H H CH3 H

H C C C C C C H

H H CH3 H CH3 H

6 5 4 3 2 1

• Naming other homologous series works in the same way.

• With those we start numbering at the end nearer the functional group e.g. this alkene:

H H H H CH3 H

H C C C C C C H

H C2H5 CH3 H

• Number the atoms in the longest carbon chain.

H H H H CH3 H

H C C C C C C H

H C2H5 CH3 H

1 2 3 4 5 6

• This now gives us the basic name – in this case hex-2-ene.

H H H H CH3 H

H C C C C C C H

H C2H5 CH3 H

1 2 3 4 5 6

• Identifying the side chains gives us the full name:

• 5,5 dimethy 4 ethyl hex-2-ene.

H H H H CH3 H

H C C C C C C H

H C2H5 CH3 H

1 2 3 4 5 6

• We can use the same principles with cyclic hydrocarbons.

H H

CH H C CH H C C H H H CH3

• 1 methyl cyclopentane H H

CH H C CH H C C H H H CH3

1

23

45

Isomers

•  Isomers are compounds with the same molecular formula but different structural formulae

• For example C4H10

H C C C C H

H H H H

H H H Hbutane

H C C C H

H H H

H C H

H

H H

2 methyl propane

Alcohols

• The alcohols form another homologous series – called the alkanols.

• We can recognise the alkanols because they contain an OH group.

• They are given names as if they are substituted alkanes.

• 3 methyl pentan-2-ol

H H CH3 H H

H C C C C C H

H H H OH H

12345

Aldehydes

• The aldehydes form another homologous series – called the alkanals.

• We can recognise the alkanals because they contain a carbonyl group at the end of the carbon chain.

• They are named as if they are substituted alkanes.

• 3,4 dimethyl pentanal• We don’t need to number the

carbonyl group because it must be on the first carbon.

H H CH3 H H

H C C C C C O

H CH3 H H

12345

Ketones

• The ketones form another homologous series – called the alkanones.

• We can recognise the alkanones because they contain a carbonyl group in the middle of the carbon chain.

• They are named as if they are substituted alkanes.

• 3,3 dimethyl pentan-2-one

H H CH3 H

H C C C C C H

H H CH3 O H

12345

Alkanoic acids

• The alkanoic acids form another homologous series.

 • Carboxylic acids are used in a

variety of ways.

Alkanoic acids

• We can recognise the alkanoic acids because they contain a COOH group.

C OH

O

• We can name the alkanoic acids using the principles we have used before.

H H CH3 H H

H C C C C C

H H H H H

C OH

O

• 4 methyl hexanoic acid• We don’t need to number the

acid group because it must be on the first carbon. H H CH3 H H

H C C C C C

H H H H H

12345C OH

O

6

Esters

• An ester can be identified the ‘-oate’ ending to its name.

• The ester group is:

C O

O

Esters

• An ester can be named given the names of the parent alkanol and alkanoic acid.

• The name also tells us the alkanoic acid and alkanol that are made when the ester is broken down.

CH3 CH2 C OH

O

The acid and alkanol combine

HO CH3

The acid and alkanol combine

CH3 CH2 C OH

O

HO CH3

The acid and alkanol combine

Water is formed.

CH3 CH2 C

O

O CH3

H2O

Naming esters

Acid name Alkanol name

Ester name

ethanoic acid methanol methyl ethanoate

propanoic acid

ethanol ethyl propanoate

butanoic acid propanol propyl butanoate

methanoic acid

butanol butyl methanoate

• A typical ester is shown below.

H H O H H

H C C C O C

H H H H

C H

• We can identify the part that came from the alkanoic acid – propanoic acid.

H H O H H

H C C C O C

H H H H

C H

• We can identify the part that came from the alkanol - ethanol

H H O H H

H C C C O C

H H H H

C H

• This gives us the name ethyl propanoate

H H O H H

H C C C O C

H H H H

C H

Aromatic Hydrocarbons

• Benzene is the simplest aromatic hydrocarbon.

• It has the formula C6H6.

• The benzene molecule has a ring structure.

• Even though benzene would seem to be unsaturated it does not decolourise bromine water.

• All the bonds in benzene are equivalent to each other – it does not have the usual kind of single and double bonds.

• The bonds in benzene are intermediate between single and double bonds.

• Their lengths and bond energies are in between those of single and double bonds.

• The stability of the benzene ring is due to the delocalisation of electrons.

• A benzene ring in which one hydrogen atom has been substituted by another group is known as the phenyl group.

• The phenyl group has the formula -C6H5.

Benzene and its related compounds are important as feedstocks.

One or more hydrogen atoms of a benzene molecule can be substituted to form a range of consumer products.

Nomenclature and Structural Formula

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Reactions of Carbon

Compounds

Saturated Hydrocarbons

• Alkanes and cycloalkanes are saturated hydrocarbons.

• Saturated hydrocarbons contain only carbon to carbon single covalent bonds.

Unsaturated Hydrocarbons

• The alkenes are unsaturated hydrocarbons.

• Unsaturated hydrocarbons contain at least one carbon to carbon double covalent bond.

Addition Reactions

• Addition reactions take place when atoms, or groups of atoms, add across a carbon to carbon double bond or carbon to carbon triple bond.

• For alkenes the basic reaction is:

H H H H

C C + * * C C

* *

• When bromine adds to an alkene we have an addition reaction.

• C4H8 + Br2 C4H8 Br2

H H H H

C C + Br Br C C

Br Br

• The addition reaction between hydrogen chlkoride and an alkene gives the equivalent alkyl chloride.

• C3H6 + HCl C3H7Cl

H H H H

C C + H Cl C C

H Cl

propene + hydrogen chloride propyl chloride

Halogenoalkanes

• Halogenoalkanes have properties which make them useful in a variety of consumer products.

• In the atmosphere, ozone, O3, forms a protective layer which absorbs ultraviolet radiation from the sun.

• The depletion of the ozone layer is believed to have been caused by the extensive use of certain CFCs (chlorofluorocarbons).

• The addition reaction between water and an alkene gives the equivalent alkanol.

• propene + water propanol

• C3H6 + H2O C3H7OH

H H H H

C C + H2O C C

H OH

Sometimes addition reactions can give two different isomeric products.

CH2=CH-CH3

CH2Cl-CH2-CH3 CH3-CHCl-CH3

HCl

Ethanol

• To meet market demand ethanol is made by means other than fermentation.

• Industrial ethanol is manufactured by the catalytic hydration of ethene. H H H

H

H C C H + H2O H C C H H OH

• Ethanol can be converted to ethene by dehydration.

• This reaction uses aluminium oxide or concentrated sulphuric acid as a catalyst.

H H H H

H C C OH C C + H2O

H H H H

• For alkynes the reaction takes place in two stages:

C C + * * C C

* *

* * * *

C C + * * C C

* *

With hydrogen:

CH CH

CH2 CH2

CH3 CH3

H2

H2

With a halogen:

CH CH

CHX CHX

CHX2 CHX2

X2

X2

With a halogen halide:

CH CH

CHX CH2

CHX2 CH3

HX

CH2X CH2X

HX

The benzene ring resists any addition reactions.

Its delocalised electrons mean that its bonds do not behave like the bonds in an unsaturated compound

Alcohols

• There are three types of alcohols:

• Primary• Secondary• Tertiary

Primary Alcohols

• Primary alcohols have at least two hydrogen atoms on the carbon atom carrying the OH group.

H

C OH

H

Secondary Alcohols

• Secondary alcohols have one hydrogen atom on the carbon atom carrying the OH group.

H

C OH

Tertiary Alcohols

• Tertiary alcohols have at no hydrogen atoms on the carbon atom carrying the OH group.

C OH

Oxidation and Reduction

• Oxidation and reduction can be described in terms of loss or gain of electrons.

• In organic chemistry it is more useful to describe them differently.

• Oxidation is an increase in the oxygen to hydrogen ratio e.g. CH3CH2OH CH3CHO

1:6 1:4

• Reduction is a decrease in the oxygen to hydrogen ratio.CH3CO2H CH3CH2OH

2:4 1:6

Oxidation Reactions

• The simplest oxidation reaction of alcohols is when they are burned in oxygen, giving carbon dioxide and water.

• Some alcohols can be oxidised to give aldehydes and ketones.

• Primary alcohols can be oxidised in two stages : first to an aldehyde

H

R C O H

H

H

R C O

Primary alcohol Aldehyde

• Primary alcohols can be oxidised in two stages : first to an aldehyde and then to an alkanoic acid.

H

R C O H

H

H

R C O

H

R C O

OH

R C O

Primary alcohol Aldehyde

Aldehyde Alkanoic Acid

• Secondary alcohols can be oxidised only once: to a ketone

R*

R C O H

H

R*

R C O

Secondary alcohol Ketone

No further oxidation is possible

• Tertiary alcohols cannot be oxidised at all.

R*

R C O H

R**

No oxidation is possible

• Aldehydes can be oxidised to give carboxylic (alkanoic) acids while ketones cannot.

• This can be used as a means of differentiating between aldehydes and ketones.

• The oxidising agents that are used most often give visible signs of reaction.

Reagent Visible effect

Acidified permanganate

Purple colourless

Acidified dichromate Orange green

Copper oxide Black brown

Tollen’s Reagent Silver mirror produced

Fehling’s solution Blue red

Benedict’s solution Blue red

Condensation Reactions

• In a condensation reaction, the molecules join together by the reaction of the functional groups to make water.

H HO

H2O

Esters

• Esters are formed by the condensation reaction between a carboxylic acid and an alcohol.

• Uses of esters include flavourings, perfumes and solvents.

Esters

• Esters can be recognised by the ester link shown below:

C O

O

• The ester link is formed by the reaction of a hydroxyl group of an alkanol with a carboxyl group of a carboxylic acid.

H H

HO C C H

H H

• The ester link is formed by the reaction of a hydroxyl group of an alkanol with a carboxyl group of a carboxylic acid.

H H

HO C C H

H H

• The ester link is formed by the reaction of a hydroxyl group of an alkanol with a carboxyl group of a carboxylic acid.

H H O

H C C C O H

H H

• The ester link is formed by the reaction of a hydroxyl group of an alkanol with a carboxyl group of a carboxylic acid.

H H O

H C C C O H

H H

H H O

H C C C O H

H HCarboxylic acid

H H

HO C C H

H HAlkanol

H H O

H C C C O H

H H

H H

HO C C H

H H

H H O

H C C C O H

H H

H H

HO C C H

H H

Water is formed from hydrogen of one molecule and hydroxide from the other.

H H O

H C C C O

H H

H H

C C H

H HH2O

Water is formed from hydrogen of one molecule and hydroxide from the other.

H H O

H C C C O

H H

H H

C C H

H HH2O

Water is formed from hydrogen of one molecule and hydroxide from the other.

The remains of the molecules join together

H H O

H C C C O

H H

H H

C C H

H HH2O

Water is formed from hydrogen of one molecule and hydroxide from the other.

The remains of the molecules join together

Hydrolysis Reactions

• In a hydrolysis reaction, a molecule is split up by adding the elements of water.

H HO

H2O

• The carboxylic acid and the alcohol from which the ester are made can be obtained by hydrolysis.

CH3CH2COOCH3 CH3CH2COOH

+ H2O + CH3OH

• The formation and hydrolysis of an ester is a reversible reaction.

Acid + alkanol Ester + water

hydrolysis

condensation

Yields

• If we write the equation for a reaction we can calculate what mass of product should be produced – the theoretical yield.

• When we carry out the experiment we can measure the mass of product produced – the actual yield.

Percentage Yield

• Percentage yield is the actual yield, expressed as a percentage of the theoretical yield.

Percentage Yield

Actual Yield

Theoretical Yield= X 1001

Percentage Yield

Actual Yield

Theoretical Yield= X 1001

Titanium dioxide, TiO2, is used in the manufacture of white paint. It is made from ilmenite, FeTiO3.If 45.1kg of TiO2 is obtained from 100kg of ilmenite, what is the percentage yield of the conversion?

FeTiO3 TiO2

1 mole 1 mole

152g 80g

1g 80/152g = 0.5263g

100kg 52.63kg

Percentage yield = 45.1 x 100 = 85.7% 52.63 1

Reactions of Carbon Compounds

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Polymers

Addition Polymerisation

• Many polymers are made from the small unsaturated molecules, produced by the cracking of oil.

• They add to each other by opening up their carbon to carbon double bonds.

• This process is called addition polymerisation.

• Ethene is a starting material of major importance in the petrochemical industry especially for the manufacture of plastics.

• It is formed by cracking the ethane from the gas fraction or the naphtha fraction from oil.

• Propene can be formed by cracking the propane from the gas fraction or the naphtha fraction from oil.

H H

C C

H HThe ethene is attacked by an initiator (I*) which opens up the double bond

I*

The ethene is attacked by an initiator (I*) which opens up the double bond

I

H H

C C*

H H

Another ethene adds on.

H H

C C

H H

The ethene is attacked by an initiator (I*) which opens up the double bond

Another ethene adds on.

I

H H

C C

H H

H H

C C*

H H

Then another

H H

C C

H H

The ethene is attacked by an initiator (I*) which opens up the double bond

Another ethene adds on.Then another

I

H H

C C

H H

H H

C C

H H

H H

C C*

H H

….

Naming polymers

• The name of the polymer is derived from its monomer.

MONOMER POLYMER ***ene poly(***ene)ethene poly(ethene)propene poly(propene)styrene poly(styrene)chloroethene poly(chloroethene)tetrafluoroethene

poly(tetrafluoroethene)

Repeat Units

• You can look at the structure of an addition polymer and work out its repeat unit and the monomer from which it was formed.

• The repeat unit of an addition polymer is always only two carbon atoms long.

-CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -

Repeat Unit CH2 -CH2

-CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -CH2 -

-CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl

-

Repeat Unit CH2 -CHCl

-CH2 -CHCl -CH2 -CHCl -CH2 -CHCl -CH2 -CHCl

-

Monomer CH2 =CH2

Monomer CH2

=CHCl

Condensation Polymers

• Condensation reactions involve eliminating water when two molecules join.

• Condensation polymers are made from monomers with two functional groups per molecule.

• Normally there are two different monomers which alternate in the structure e.g.

H H

and

HO OH

• The molecules join together, eliminating water as they do so.

• Hydrogen comes from one molecule.

• Hydroxide comes from the other molecule.

• The molecules join where these groups have come off.

H HHO OH

H OH

H2O

H H

H H

H2O H2O

HO OH

H

H2O H2O H2O

OHH H

H

H2O H2O H2O H2O

HHO OH

H OH

H2O H2O H2O H2O H2O

Repeat Units

• You can look at the structure of a condensation polymer and work out its repeat unit and the monomers from which it was formed.

-C-(CH2)4-C-N-(CH2)6-N -C-(CH2)4-C-N-(CH2)6-N-

O O H H O O H H

-C-(CH2)4-C-N-(CH2)6-N-

O O H H

-C-(CH2)4-C-N-(CH2)6-N -C-(CH2)4-C-N-(CH2)6-N-

O O H H O O H H

HO-C-(CH2)4-C-OH

O O

H-N-(CH2)6-N-H

H H

Polymer

Repeat Unit

Monomers

and

Polymer

Repeat Unit

Monomers

and

-O-C-C6H4-C-O-CH2-CH2 -O-C-C6H4-C-O-CH2-CH2-

O O 0 O

HO-CH2-CH2 -OH

-O-C-C6H4-C-O-CH2-CH2 -O-C-C6H4-C-O-CH2-CH2-

O O 0 O

H-O-C-C6H4-C-O-H

O O

-O-C-C6H4-C-O-CH2-CH2-

O O

Condensation Polymers

• Typical condensation polymers are polyesters and polyamides.

• Terylene is the brand name for a typical polyester.

Polyesters

• As the name suggests polyesters are polymers which use the ester link.

• The two monomers which are used are a diacid and a diol.

The diacid will have a typical structure:

The diol will have a typical structure:

HO OH

They combine like this:

C-O-H

O

H-O-C

O

C-O-H

O

H-O-C

O

The diacid will have a typical structure:

The diol will have a typical structure:

HO OH

They combine like this:

C-O-H

O

H-O-C

O

C-O-H

O

H-O-C

O

HO OH

The diacid will have a typical structure:

The diol will have a typical structure:

HO OH

They combine like this:

C-O-H

O

H-O-C

O

C-O

O

H-O-C

O

OH C-O-H

O

H-O-C

O

The diacid will have a typical structure:

The diol will have a typical structure:

HO OH

They combine like this:

C-O-H

O

H-O-C

O

C-O

O

H-O-C

O

O C-O-H

O

-C

O

HO OH

The diacid will have a typical structure:

The diol will have a typical structure:

HO OH

They combine like this:

C-O

O

H-O-C

O

O C-O

O

-C

O

OH

C-O-H

O

H-O-C

O

• Polyesters are manufactured for use as textile fibres and resins.

• Polyesters used for textile fibres have a linear structure.

• Cured polyester resins have a three-dimensional structure. Cross linking between the polyester chains makes the structure much more rigid.

Amines

• Amines are a homologous series containing the amine group:

N H

H

The amide link

• The amide link is formed when an acid and amine join together.

N H

H

HO C

O

The amide link

• The amide link is formed when an acid and amine join together.

N H

H

HO C

O

The amide link

• The amide link is formed when an acid and amine join together.

N

H

C O

H2O

The amide link

• The amide link is formed when an acid and amine join together.

N

H

C O

The amide link

Polyamides

• A polyamide is made from a diamine and a diacid:

H N

H

N H

Hdiamine

C-O-H

O

H-O-C

O

diacid

They combine like this:

H N

H

N H

H

C-O-H

O

H-O-C

O

H N

H

N H

H

H N

H

N

H

C-O-H

O

C

O

H2O

C-O-H

O

H-O-C

O

H N

H

N

H

C

O

C

O

N

H

N H

H

H2O H2O

H N

H

N

H

C

O

C

O

N

H

N

H

C-O-H

O

C

O

H2O H2O H2O

• Nylon is a typical polyamide.• Nylon is a very important

engineering plastic.• The strength of nylon is caused

by hydrogen bonding between the polymer chains.

Synthesis gas

• Synthesis gas can be obtained by steam reforming of methane from natural gas.

CH4 + H2O CO + 3H2

• It can also be made by the steam reforming of coal.

• Methanol, used in the production of methanal, is made industrially from synthesis gas.

• Methanal is an important feedstock in the manufacture of thermosetting plastics.

• It is used to assist cross-linking so as to make thermosetting plastics and resins.

New polymers

• Kevlar is an aromatic polyamide which is extremely strong because of the way in which the rigid, linear molecules are packed together.

• These molecules are held together by hydrogen bonds.

• Kevlar has many important uses.

• Poly(ethenol) is a plastic which readily dissolves in water. It has many important uses

• It is made from another plastic by a process known as ester exchange.

• The percentage of acid groups which have been removed in the production process affects the strengths of the intermolecular forces upon which the solubility depends.

• Poly(ethyne) can be treated to make a polymer which conducts electricity.

• The conductivity depends on delocalised electrons along the polymer chain.

• Poly(vinyl carbazole) is a polymer which exhibits photoconductivity and is used in photocopiers.

• Biopol is an example of a biodegradable polymer.

• The structure of low density polythene can be modified during manufacture to produce a photodegradable polymer.

Polymers

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Natural Products

Fats and Oils

• Natural fats and oils can be classified according to where they come from:

• Animal• Vegetable• Marine

• Fats and oils in the diet supply the body with energy.

• They are a more concentrated source of energy than carbohydrates.

• Oils are liquids and fats are solids.• Oils have lower melting points

than fats. • This is because oil molecules have

a greater degree of unsaturation.

Saturated fats:

have more regular shapes than unsaturated oils:

Fat molecules close pack together easily and have a low melting point

Oil molecules do not close pack together so easily and have a high melting point

Oils can be converted into hardened fats by adding of hydrogen.

H2

H2

H2

Oils can be converted into hardened fats by adding of hydrogen.

This is how margarine is made

Fatty acids

• Fatty acids are straight chain carboxylic acids, containing even numbers of carbon atoms from C4 to C24, primarily C16 and C18.

• Fatty acids may be saturated or unsaturated.

• Fats and oils are esters.• They are made from the triol

glycerol (propan-1,2,3-triol)

CH2 OH

CH OH

CH2 OH

glycerol

and fatty acids.

R C OH

Ofatty acid

• Fats and oils are esters.• They are made from the triol

glycerol (propan-1,2,3-triol)

CH2 OH

CH OH

CH2 OH

glycerol

and fatty acids.

fatty acid

HO C R

O

HO C R3

O

CH2 OH

CH OH

CH2 OH

HO C R2

O

HO C R1

O

Three fatty acids form esters with the three OHgroups of glycerol.

C R3

O

CH2 O

CH

CH2 O

O C R2

O

C R1

O

Three fatty acids form esters with the three OHgroups of glycerol.

• The hydrolysis of fats and oils produces fatty acids and glycerol in the ratio of three moles of fatty acid to one mole of glycerol.

C R

O

CH2 O

CH

CH2 O

O C R

O

C R

OCH2 OH

CH OH

CH2 OH

R C OH

O

+ 3

Fats and oils

• Fats and oils consist largely of mixtures of triglycerides.

• The three fatty acid molecules combined with each molecule of glycerol need not be the same.

• Soaps are produced by the hydrolysis of fats and oils.

Proteins

• Nitrogen is needed to make protein in plants and animals.

• Proteins are condensation polymers made up of many amino acid molecules linked together.

• The structure of the protein is based on the constituent amino acids.

Amino acids

• These are compounds which contain an amine group and an acid group.

N H

H

R

HO C C

O H

• There are about 25 essential amino acids.

• They are different because they have different side groups – shown by “R”.

• Condensation of amino acids produces the peptide (amide) link.

N H

H

R

HO C C

O H

The peptide link

• The peptide link is formed when an acid and amine join together. (We have previously called this the amide link.)

N H

H

R1

HO C C

O H

N H

H

R2

HO C C

O H

The peptide link

• The peptide link is formed when an acid and amine join together. (We have previously called this the amide link.)

N

H

R1

HO C C

O H

N H

H

R2

C C

O H

peptidelink

Amino acids polymerising

N H

H

R1

HO C C

O H

N H

H

R2

HO C C

O H

Amino acids polymerising

N

H

R1

HO C C

O H

N H

H

R2

C C

O H

H2O

N H

H

R3

HO C C

O H

Amino acids polymerising

N

H

R1

HO C C

O H

N

H

R2

C C

O H

H2O

N H

H

R3

C C

O H

H20

N H

H

R4

HO C C

O H

Amino acids polymerising

N

H

R1

HO C C

O H

N

H

R2

C C

O H

H2O

N

H

R3

C C

O H

H20

N H

H

R4

C C

O H

H2O

Building proteins

• Proteins specific to the body’s needs are built up within the body.

• The body cannot make all the amino acids required for body.

• We need protein in our diet to supply certain amino acids known as essential amino acids.

Digestion

• During digestion enzymes hydrolyse the proteins in our diet to produce amino acids.

• The body then builds up the amino acids it needs from those amino acids.

H2ON

H

R1

HO C C

O H

N

H

R2

C C

O H

N

H

R3

C C

O H

N H

H

R4

C C

O H

H2ON

H

R1

HO C C

O H

N

H

R2

C C

O H

N H

H

R3

C C

O H

N H

H

R4

HO C C

O H

H2ON

H

R1

HO C C

O H

N H

H

R2

C C

O H

N H

H

R3

HO C C

O H

N H

H

R4

HO C C

O H

HO

N H

H

R1

HO C C

O H

N H

H

R2

C C

O H

N H

H

R3

HO C C

O H

N H

H

R4

HO C C

O H

Hydrolysis

• The structural formulae of amino acids obtained from the hydrolysis of proteins can be identified from the structure of a section of the protein as shown in the last few slides.

Types of proteins

• Proteins can be classified as fibrous or globular.

• Fibrous proteins are long and thin and are the major structural materials of animal tissue – muscles, tissues etc.

• Globular proteins have the spiral chains folded into compact units.

• Globular proteins are involved in the maintenance and regulation of life processes and include enzymes and many hormones, eg insulin and haemoglobin.

Enzymes

• Enzymes, such as amylase, are biological catalysts

• An enzyme will work most efficiently within very specific conditions of temperature and pH.

• The further conditions are removed from the ideal the less efficiently the enzyme will perform.

• What an enzyme can do is related to its molecular shape.

• Denaturing of a protein involves physical alteration of the molecules as a result of temperature change or pH change.

• The ease with which a protein is denatured is related to the fact that enzymes are very sensitive to changes in temperature and pH.

Natural Products

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The End

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