Compounds of Compounds of CarbonCarbonChapter 8Chapter 8

Why is carbon important?Why is carbon important? Carbon makes up over 90% of all Carbon makes up over 90% of all

chemical compounds chemical compounds They form the basis of living systemsThey form the basis of living systems

– Carbohydrates all have carbonCarbohydrates all have carbon– Proteins contain carbonProteins contain carbon– Fats contain carbonFats contain carbon

How does carbon form so How does carbon form so many compounds?many compounds?

Carbon has 4 valence electrons, all Carbon has 4 valence electrons, all available for bonding with other available for bonding with other atomsatoms

Carbon can form strong covalent Carbon can form strong covalent bonds with other carbon atomsbonds with other carbon atoms

Bonds between carbons can be Bonds between carbons can be single or multiplesingle or multiple

HydrocarbonsHydrocarbons Hydrocarbons are made up of different Hydrocarbons are made up of different

compounds of hydrogen and carbon.compounds of hydrogen and carbon. There are many different hydrocarbonsThere are many different hydrocarbons They make up the majority of the They make up the majority of the

petroleum and natural gas industry petroleum and natural gas industry Hydrocarbons can be classified into Hydrocarbons can be classified into

several families or homologous groups. several families or homologous groups. The simplest hydrocarbon is methane The simplest hydrocarbon is methane

and it belongs to the alkane series.and it belongs to the alkane series.

Homologous groupsHomologous groups A series of compounds with similar A series of compounds with similar

properties in which each member properties in which each member differs form the previous one by –CHdiffers form the previous one by –CH22- - is called a is called a homologoushomologous group group

Members of the same homologous Members of the same homologous groups tend to have very similar groups tend to have very similar chemical properties. So organising chemical properties. So organising carbon compounds into homologous carbon compounds into homologous series simplifies the study of series simplifies the study of hydrocarbons.hydrocarbons.

AlkanesAlkanes Alkanes consist of carbon and Alkanes consist of carbon and

hydrogen only.hydrogen only. They contain only single bondsThey contain only single bonds Look at the table, each alkane Look at the table, each alkane

differs by –CHdiffers by –CH22- - The alkanes have a general The alkanes have a general

formula of Cformula of CnnHH2n+22n+2 If a compound has 16 carbons, If a compound has 16 carbons,

then 2 x 16 + 2 = 34then 2 x 16 + 2 = 34 So it would have the fomula CSo it would have the fomula C1616HH3434

Representing alkane Representing alkane moleculesmolecules

When drawing hydrocarbons we use When drawing hydrocarbons we use structural formulasstructural formulas

These are very similar to valence These are very similar to valence structures except they don’t show the structures except they don’t show the unbonded pairs.unbonded pairs.

In structural formulas we focus on the In structural formulas we focus on the location of the atoms relative to one location of the atoms relative to one another in the molecule as well as the another in the molecule as well as the number and location of chemical number and location of chemical bonds.bonds.

The above diagram shows the first The above diagram shows the first three alkanes.three alkanes.

You will notice:You will notice:– Each carbon atom forms a single covalent Each carbon atom forms a single covalent

bond to four other atomsbond to four other atoms– Each hydrogen atom forms a single Each hydrogen atom forms a single

covalent bond to one carbon atomcovalent bond to one carbon atom– The four atoms bonded to each carbon The four atoms bonded to each carbon

atom are arranged in a tetrahedral shape.atom are arranged in a tetrahedral shape.

Your TurnYour Turn How would we draw the structural How would we draw the structural

formula for Cformula for C44HH1010

There are two possible ways.There are two possible ways. The first has the four carbon atoms in a The first has the four carbon atoms in a

continuous chain. The overall molecule continuous chain. The overall molecule is said to be linear.is said to be linear.

These are called straight-chain These are called straight-chain moleculesmolecules

The second one is not linear, this is The second one is not linear, this is called a branched chain moleculecalled a branched chain molecule

IsomerIsomer Molecules which have the same Molecules which have the same

chemical formula but can form chemical formula but can form different arrangements of their different arrangements of their atoms are called isomers.atoms are called isomers.

Same number of atoms just arranged Same number of atoms just arranged differently.differently.

Structural isomers have similar Structural isomers have similar chemical properties but can differ in chemical properties but can differ in some physical properties such as some physical properties such as melting and boiling temperaturesmelting and boiling temperatures

AlkanesAlkanes The alkane series contains only single The alkane series contains only single

bonds.bonds. The alkanes are known to be The alkanes are known to be

saturated hydrocarbons as the saturated hydrocarbons as the carbons are saturated with hydrogenscarbons are saturated with hydrogens

Meaning each carbon is completely Meaning each carbon is completely bonded to either hydrogen or carbon, bonded to either hydrogen or carbon, there are no unbonded carbons.there are no unbonded carbons.

AlkenesAlkenes Alkenes contains one double bond Alkenes contains one double bond

between two carbons.between two carbons. Like alkanes, alkenes also differ by one Like alkanes, alkenes also differ by one

–CH–CH22- group.- group. The alkenes also form a homologous The alkenes also form a homologous

series.series. The alkenes generally have the formula The alkenes generally have the formula

CCnnHH2n2n..

Representing Alkene Representing Alkene MoleculesMolecules

Like ethene, propene CLike ethene, propene C33HH66 also has also has one carbon-carbon double bond.one carbon-carbon double bond.

ButeneButene Butene (CButene (C44HH88), like butane has more than ), like butane has more than

one isomer.one isomer.

The alkenes are classified as unsaturated The alkenes are classified as unsaturated hydrocarbons. The double bond means hydrocarbons. The double bond means that alkenes contain less hydrogen than that alkenes contain less hydrogen than the maximum amount possible.the maximum amount possible.

Semistructural formulasSemistructural formulas When we want to summarise the When we want to summarise the

structural formula without indicating structural formula without indicating the 3D arrangement we use the 3D arrangement we use semistructural formulas.semistructural formulas.

The semi structural The semi structural Formula for propene is Formula for propene is CC33HH66

Your TurnYour Turn Page 140 Page 140 Questions 3 - 6Questions 3 - 6

Naming Carbon CompoundsNaming Carbon Compounds How do we name carbon How do we name carbon

compounds?compounds? How do we distinguish between How do we distinguish between

structural isomers?structural isomers? There are a set of rules put in place There are a set of rules put in place

by which chemists can derive a by which chemists can derive a systematic name for a given systematic name for a given compound.compound.

No of C atomsNo of C atoms PrefixPrefix11 meth-meth-22 eth-eth-33 prop-prop-44 but-but-55 pent-pent-66 hex-hex-77 hept-hept-88 oct-oct-99 non-non-

1010 dec-dec-

Straight-chain hydrocarbonsStraight-chain hydrocarbons The first part of the name refers to the The first part of the name refers to the

number of hydrocarbons.number of hydrocarbons. The second part refers to type of bondsThe second part refers to type of bonds

– ane if all carbon-carbon bonds are singleane if all carbon-carbon bonds are single– ene if one C-C bond is a doubleene if one C-C bond is a double– yne if one C-C bond is a tripleyne if one C-C bond is a triple

Pentane, pentene and pentyne all have 5 Pentane, pentene and pentyne all have 5 carbons bonded in a linear or straight chain.carbons bonded in a linear or straight chain.

Unsaturated compoundsUnsaturated compounds Unsaturated hydrocarbons contain at least one Unsaturated hydrocarbons contain at least one

multiple bond.multiple bond. Butene has three isomers, two of which are Butene has three isomers, two of which are

straight chained, as the carbon chain becomes straight chained, as the carbon chain becomes longer the number of isomers increases.longer the number of isomers increases.

To name straight-chain alkenes, first number To name straight-chain alkenes, first number the carbon atoms in the chain, starting with the carbon atoms in the chain, starting with the end that will give the first carbon atom the end that will give the first carbon atom involved in the double bond the smallest involved in the double bond the smallest number possible.number possible.

The number starts at the The number starts at the end closest to the double end closest to the double bond.bond.

The isomer is named The isomer is named according to the first according to the first carbon atom involved in carbon atom involved in the double bond.the double bond.

The first isomer is but-1-The first isomer is but-1-ene.ene.

The other isomer is but-2-The other isomer is but-2-eneene

Branched HydrocarbonsBranched Hydrocarbons An alkyl group usually forms a branch An alkyl group usually forms a branch

in a branched chain hydrocarbon.in a branched chain hydrocarbon. An alkyl group is an alkane molecule An alkyl group is an alkane molecule

less on hydrogen atom less on hydrogen atom It is named after the alkane from It is named after the alkane from

which it is derived. which it is derived. -CH-CH33 is a methyl group. is a methyl group. -C-C22HH55 (-CH (-CH22CHCH33) is an ethyl group) is an ethyl group

Branched HydrocarbonsBranched Hydrocarbons Systematic naming requires us to:Systematic naming requires us to:

– Identify the longest continuous chain of Identify the longest continuous chain of carbon atoms in a molecule.carbon atoms in a molecule.

– Identify the side group that forms the Identify the side group that forms the branch in the chainbranch in the chain

– Number the carbon atoms from one of the Number the carbon atoms from one of the ends of the longest carbon chain so that ends of the longest carbon chain so that the side group is attached to the carbon the side group is attached to the carbon atom with the smallest possible number.atom with the smallest possible number.

CC44HH1010

The longest chain of carbons has 3 The longest chain of carbons has 3 carbons and all the bonds are single. carbons and all the bonds are single. – Therefore the molecule is derived from Therefore the molecule is derived from

propane.propane. Identify the side groupIdentify the side group

– The side group is a methyl group.The side group is a methyl group. Number the carbons. The methyl group is Number the carbons. The methyl group is

on the second carbon.on the second carbon. The compound is therefore 2-The compound is therefore 2-

methylpropane.methylpropane.

Worked Example 8.4, page Worked Example 8.4, page 143143

Some are done for usSome are done for us Take a look at page 144 of your text.Take a look at page 144 of your text. Which are the alkanes?Which are the alkanes? Which are the alkenes?Which are the alkenes?

Functional GroupsFunctional Groups -CH-CH33 – methyl – methyl -OH – alkanol -OH – alkanol -Cl (or F, or B or I) chloro (or fluoro -Cl (or F, or B or I) chloro (or fluoro

etc)etc) -NH-NH22 - amino - amino

Your TurnYour Turn Page 147Page 147 Questions 7 and 8Questions 7 and 8

Chemical Properties of Chemical Properties of AlkanesAlkanes

The most significant reaction of alkanes The most significant reaction of alkanes is combustion. Alkanes burn in oxygen, is combustion. Alkanes burn in oxygen, releasing large quantities of energy.releasing large quantities of energy.

If the oxygen supply is sufficient the If the oxygen supply is sufficient the products released are carbon dioxide products released are carbon dioxide and water. and water.

This energy released is what we use as This energy released is what we use as a source of heat, to produce electricity a source of heat, to produce electricity for domestic and industrial use.for domestic and industrial use.

Equations for Combustion of Equations for Combustion of ReactionsReactions

This figure shows the rearrangement of atoms that occur This figure shows the rearrangement of atoms that occur when the hydrocarbon methane burns in oxygen.when the hydrocarbon methane burns in oxygen.

Have the atoms of each element been conserved?Have the atoms of each element been conserved?The equation isThe equation isCHCH44 + 2O + 2O22 →→ CO CO22 + 2H + 2H22OO

Chemical Properties of Chemical Properties of AlkenesAlkenes

Due to the double bond in alkenes they Due to the double bond in alkenes they react much more readily and with more react much more readily and with more chemicals than the alkanes.chemicals than the alkanes.

Alkenes, in particular, ethene and propene, Alkenes, in particular, ethene and propene, are not used for fuels but rather as starting are not used for fuels but rather as starting materials to manufacture a huge range of materials to manufacture a huge range of compounds such as alcohols, antifreeze compounds such as alcohols, antifreeze and plastics.and plastics.

Apart from combustion, the reactions of Apart from combustion, the reactions of alkenes usually involve the addition of a alkenes usually involve the addition of a small molecule to produce a single product.small molecule to produce a single product.

Addition reactions of etheneAddition reactions of ethene

Reaction with Bromine solutionReaction with Bromine solution– Ethene reacts with bromine solution as Ethene reacts with bromine solution as

shown.shown.– In addition reactions, bonding “new” In addition reactions, bonding “new”

atoms to the two carbons on either side atoms to the two carbons on either side of the double bond, converts the C=C of the double bond, converts the C=C double bond to a C-C single bond.double bond to a C-C single bond.

Reaction with SteamReaction with Steam

Large amounts of ethanol are now made Large amounts of ethanol are now made by the addition of steam and ethene using by the addition of steam and ethene using a phosphoric acid catalyst.a phosphoric acid catalyst.

This ethanol is used as a reagent for This ethanol is used as a reagent for industrial purposes and as a solvent in industrial purposes and as a solvent in cosmetics and pharmaceuticals.cosmetics and pharmaceuticals.

This is not the ethanol that people drink.This is not the ethanol that people drink.

Formation of polyetheneFormation of polyethene An addition reaction of ethene is An addition reaction of ethene is

involved in making polyethene. involved in making polyethene. As seen previously the C=C bond is As seen previously the C=C bond is

converted to a C-C bond and a converted to a C-C bond and a saturated product is formed.saturated product is formed.

In this case there is no other reactant In this case there is no other reactant to add to the ethene molecules. to add to the ethene molecules. Polyethene is formed when ethene Polyethene is formed when ethene molecules themselves join together molecules themselves join together to form a long chain.to form a long chain.

Polyethene is usually written as (-CHPolyethene is usually written as (-CH22-CH-CH22-)-)nn Where n is a large numberWhere n is a large number A molecule made by linking a large number of A molecule made by linking a large number of

small molecules such as ethene is called a small molecules such as ethene is called a polymer (meaning many units). Each small polymer (meaning many units). Each small molecule is called a monomer (one unit). molecule is called a monomer (one unit).

This type of reaction is addition polymerisationThis type of reaction is addition polymerisation

Your TurnYour Turn Page 151Page 151 Questions 9-10Questions 9-10

PolymersPolymers Polymers are long chained moleculesPolymers are long chained molecules Each one can contain tens of thousands Each one can contain tens of thousands

of atoms.of atoms. Cotton, wool and silk are some naturally Cotton, wool and silk are some naturally

occurring polymers.occurring polymers. Synthetically made polymers are Synthetically made polymers are

generally superior to natural polymers generally superior to natural polymers as they have been designed for specific as they have been designed for specific properties.properties.

Synthetic polymersSynthetic polymersInclude:Include:

– Cling wrapCling wrap– DrugsDrugs– ClothingClothing– Domestic appliancesDomestic appliances– CarsCars– Sporting equipmentSporting equipment

Check out table 8.8 on page 153Check out table 8.8 on page 153

Not PlasticNot Plastic We frequently use the term plastic when We frequently use the term plastic when

referring to polymers.referring to polymers. The term “plastic” refers to the property of The term “plastic” refers to the property of

a material not the material itself.a material not the material itself. A substance is “plastic” if it can be A substance is “plastic” if it can be

moulded into different shapes easily.moulded into different shapes easily. Many polymers are indeed plastic, some Many polymers are indeed plastic, some

however are not.however are not. The materials used to make powerpoints The materials used to make powerpoints

are brittle and cannot be reshaped.are brittle and cannot be reshaped.

What are polymers?What are polymers? Polymers are large covalently bonded Polymers are large covalently bonded

molecules.molecules. They contain tens of thousands of atomsThey contain tens of thousands of atoms They are formed by joining together They are formed by joining together

smaller molecular units called smaller molecular units called monomers.monomers.

The size of the polymer varies, a The size of the polymer varies, a polymer can consist of varying sizes of polymer can consist of varying sizes of molecules formed from different molecules formed from different numbers of monomers.numbers of monomers.

PolymersPolymers There are two types of polymerisation There are two types of polymerisation

processes.processes.– Addition polymerisationAddition polymerisation– Condensation polymerisationCondensation polymerisation

The polymers formed by addition The polymers formed by addition polymerisation often have the monomer polymerisation often have the monomer included in the name of the polymer.included in the name of the polymer.

Polyethene is formed by the monomer Polyethene is formed by the monomer ethene.ethene.

Condensation polymers are named after Condensation polymers are named after the chemical bond they form.the chemical bond they form.

Polyesters contain monomers joined by an Polyesters contain monomers joined by an ester functional groupester functional group

Addition PolymersAddition Polymers Most polymers are built around Most polymers are built around

atoms of carbon like their monomers. atoms of carbon like their monomers. Covalent bonds form between the Covalent bonds form between the

monomers to produce a polymer monomers to produce a polymer molecule.molecule.

Addition PolymersAddition Polymers Suitable monomers for addition Suitable monomers for addition

polymerisation are unsaturated polymerisation are unsaturated molecules.molecules.

What are unsaturated molecules?What are unsaturated molecules? The double bond between the two carbon The double bond between the two carbon

atoms react and new covalent bonds are atoms react and new covalent bonds are formed between carbon atoms on nearby formed between carbon atoms on nearby molecules creating long chains.molecules creating long chains.

PolyethenePolyethene Read page 155 – 156.Read page 155 – 156.

Why is High-density polyethene Why is High-density polyethene stronger and more rigid than low-stronger and more rigid than low-density polyethene?density polyethene?

Structure, properties and Structure, properties and applicationsapplications

Two very important properties of polymers are Two very important properties of polymers are tensile strength and softening temperature.tensile strength and softening temperature.

Tensile strength is a measure of the materials Tensile strength is a measure of the materials resistance to breaking under tension. It resistance to breaking under tension. It determines the structural uses of the polymer.determines the structural uses of the polymer.

The softening point affects the way the The softening point affects the way the polymer can be moulded.polymer can be moulded.

Both tensile strength and softening point are Both tensile strength and softening point are determined by the strength of the forces determined by the strength of the forces between polymer chains.between polymer chains.

ThermoplasticsThermoplastics Thermoplastics are polymers that Thermoplastics are polymers that

can be moulded and shaped.can be moulded and shaped. The tensile strength and softening The tensile strength and softening

point are affected by:point are affected by:– Degree of branchingDegree of branching– Nature of atoms of groups of atoms Nature of atoms of groups of atoms

attached to the carbon chainattached to the carbon chain– How the atoms or groups of atoms are How the atoms or groups of atoms are

arranged along the chain.arranged along the chain.

Cross-linkingCross-linking Another factor that affects the Another factor that affects the

properties of a polymer is cross-properties of a polymer is cross-linking. A cross-link is a covalent linking. A cross-link is a covalent bond between polymer chains.bond between polymer chains.

The more cross-links the stronger The more cross-links the stronger and rigid the polymer.and rigid the polymer.

The strong covalent bonds in 3D bind The strong covalent bonds in 3D bind all the atoms together to form one all the atoms together to form one large lattice.large lattice.

ThermosetsThermosets Thermosets are polymers with Thermosets are polymers with

extensive cross-linking.extensive cross-linking. They do not soften on heating as They do not soften on heating as

thermoplastics do. thermoplastics do. When heat is applied the covalent When heat is applied the covalent

bonds break and the thermosetting bonds break and the thermosetting polymer will decompose rather than polymer will decompose rather than soften.soften.

Degree of branchingDegree of branching Low denisty polyethene contains a Low denisty polyethene contains a

higher degree of branching which higher degree of branching which lowers the density, hardness and lowers the density, hardness and melting point of a polymer.melting point of a polymer.

Low denisty polyethene is more Low denisty polyethene is more flexible and is used in cling wraps and flexible and is used in cling wraps and squeeze bottles.squeeze bottles.

High density polyethene is harder and High density polyethene is harder and less flexible, used in pipes and toysless flexible, used in pipes and toys

Nature of side groupsNature of side groups Look at table 8.9 on page 156.Look at table 8.9 on page 156. Which are the bulky side groups Which are the bulky side groups

which would lower density by getting which would lower density by getting in the way?in the way?

These bulky side groups prevent the These bulky side groups prevent the chains from stacking close together chains from stacking close together and forming strong rigid structures.and forming strong rigid structures.

Your TurnYour Turn Question 15Question 15 Page 160Page 160

Cross-linkingCross-linking Cross linking involves breaking the Cross linking involves breaking the

double bond in a polymer and using double bond in a polymer and using this double bond to bond to carbons this double bond to bond to carbons in the next chain.in the next chain.

Extensive cross-linkingExtensive cross-linking Where there is extensive cross-linking Where there is extensive cross-linking

the structure will be rigid and cannot the structure will be rigid and cannot be re-shaped.be re-shaped.

Thermosetting polymers have Thermosetting polymers have extensive cross-linking. extensive cross-linking.

They char and burn when heated. They char and burn when heated. They contain covalent bonds between They contain covalent bonds between

the chains as well as within the chainsthe chains as well as within the chains

Occasional cross-linkingOccasional cross-linking Elastomers are polymers that can be Elastomers are polymers that can be

stretched or pulled out of shape and stretched or pulled out of shape and then will regain their original shape. then will regain their original shape.

They contain covalent bonds within the They contain covalent bonds within the chains.chains.

They only contain a few covalent bonds They only contain a few covalent bonds between chains.between chains.

They only have occasional cross-linking.They only have occasional cross-linking.

Guess WhatGuess What We have finished unit 1We have finished unit 1 WOOHOO.WOOHOO. be prepared for a topic testbe prepared for a topic test