Compounds of Carbon Chapter 8. Why is carbon important? Carbon makes up over 90% of all chemical compounds Carbon makes up over 90% of all chemical compounds.

Compounds of Compounds of CarbonCarbon

Chapter 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 –differs form the previous one by –CHCH22- 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 So it would have the fomula

CC1616HH3434

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.

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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 The first has the four carbon atoms in

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

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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 PrefixPrefix

11 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 carbons bonded in a linear or straight chain.chain.

Unsaturated compoundsUnsaturated compounds

Unsaturated hydrocarbons contain at least Unsaturated hydrocarbons contain at least one multiple bond.one multiple bond.

Butene has three isomers, two of which are Butene has three isomers, two of which are straight chained, as the carbon chain straight chained, as the carbon chain becomes longer the number of isomers becomes longer the number of isomers increases.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 Number the carbon atoms from one of

the ends of the longest carbon chain so the ends of the longest carbon chain so that the side group is attached to the that the side group is attached to the carbon atom with the smallest possible carbon atom with the smallest possible number.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

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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 is

CHCH44 + 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

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Page 151Page 151 Questions 9-10Questions 9-10

PolymersPolymers

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

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

naturally occurring polymers.naturally 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 as they have been designed for specific properties.specific properties.

Synthetic polymersSynthetic polymers

Include: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.

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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 They contain covalent bonds within the chains.the chains.

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

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