section 3: organic chemistry AS level

What is organic chemistry?

The study of carbon containing compounds

Why does carbon form a vast number of compounds?

Because it can form strong covalent bonds with other carbon atoms, A property known as catenation

This allows carbon atoms to form long chains and rings

Define homologous series

A group of organic compounds that have the same functional group but each successive number differs by CH2. They have the same general formula and similar chemical reactivity, Members have gradually changing physical properties such as boiling point melting point and density

As a homologous series is ascending, does the size of the molecule increase or decrease?

Increase and this affects physical properties

What is a functional group?

An atom or group of atoms responsible for the characteristic reactions of an organic compound; Determine the physical and chemical properties of molecules

What is the functional group for an alkene?

R-CH=CH2

What is the functional group for halogenoalkane?

R-X where X=F, Cl, Br or I

What is the functional group for alcohols?

R-OH

What is the functional group for aldehyde?

R-CHO

What is the functional group for ketone?

R-COR

Where is the Functional group for carboxylic acid?

R-COOH

What is the functional group For esters?

R-COOR

What is the functional group for amines?

R-NH2

What is the functional group for nitriles?

R-C≡N

Define hydrocarbon

Compounds made of hydrogen and carbon only for example, methane ethane propane and butane

What is the general formula?

Formula that represents a homologous series of compounds using letters and numbers

What is a structural formula?

A formula that shows how the atoms are bonded to each carbon atom in a molecule

What is a displayed formula?

A 2-D representation of an organic molecule showing all its atoms and their bonds

What is the skeletal formula?

A simplified displayed formula with all the carbon and hydrogen bonds removed

• Carbon atoms are shown as angles or ends of the chain

• Functional groups must be shown and all atoms other than carbon must be shown

• Heteroatoms for example, the OH of an alcohol must stay visible

• Bonds are shown by the line lines

Give the formula for all the required organic compounds

What is systematic nomenclature?

Used to name organic compounds, making them easier to identify and refer to

How are positions of sidechains or functional groups indicated in organic nomenclature?

Number the carbon atoms in the longest chain starting from the end that gives the lowest possible numbers in the name

How is the side chain named?

Add the suffix -yl to the alkane stem groups of this type are called Alkyl groups

What prefixes are used when more Than one identical alkyl Side chain of functional group is present?

Di, tri and tetra are used before the group name

What does hyphen and comma separate?

The-separates numbers and words whilst comma separate numbers e.g. 3,3,4- trimethyl hexane

What happens if there is more than one type of alkyl Side chain?

They are listed in alphabetical order e.g. 4- ethyl-2-methyl hexane

How many carbon atoms does methyl have?

1

How many carbon atoms does ethyl have?

2

What prefix or suffix is used for the class alkane?

-ane

What prefix or suffix is used for the class alkene?

-ene

What is the prefix all suffix for the class Halogenoalkane?

Fluoro-, chloro-, bromo-, iodo-

What is the prefix or suffix for the class alcohol?

Hydroxy- or -ol

What is the prefix or suffix for the class aldehyde?

-al

What is the prefix or suffix for the class ketone?

-one

What is the prefix or suffix for the class carboxylic acid?

-oic acid

What is the prefix or suffix for the class ester?

-oate

What is the prefix or suffix for the class amine?

-amine

What is the prefix of the suffix for the class nitrile?

-nitrile

What are aliphatic compounds?

Straight branched or cyclic Organic compounds that do not contain a benzene ring

What is a straight chain organic molecule and give an example?

Those in which the carbon atoms are connected in one continuous chain

What is a branched organic molecule and give an example?

They have side groups attached to the main chain of carbon atoms

What is a cyclic organic molecule and give an example?

Carbon atoms are connected in a ring shape

What are structural isomers?

They have the same molecular formula but different structural formula

What are the three different types of structural isomers?

Chain isomerism, Positional isomerism and functional group isomerism

What is chain isomerism?

Same molecular formula made up of the same atoms, but the largest hydrocarbon chain is not the same. This is caused by branching, for example pentane and 2,2-dimethylpropane

What is positional isomerism?

These arise from differences in the position of a functional group in each isomer. The functional group can be located on different carbons e.g. butan-1-ol and butan-2-ol

What is functional group isomerism?

When different functional groups results in the same molecular formula, functional group isomers arise. These items have very different chemical properties as they have different functional groups e.g. butanol and ethoxyethane

What are stereoisomers?

Compounds that have the same atoms connected; However, the atoms are arranged differently in space

What causes E/Z isomerism?

Restricted rotation about the planner C=C double bond

When does E/Z isomerism occur?

When each carbon in the C=C Bond has two different groups because the double bond prevents rotation and locks the groups in position

What is E/Z nomenclature used for?

To distinguish between E/Z isomers

What is a Z isomer?

The highest priority groups are on the same side, for example both above or both below of the double bond/carbon ring

What are E isomers?

They have the highest priority groups on opposite sides of the double bond, for example, one above and one below

Describe the difference between E/Z isomers and cis/trans.

Cis/trans: same or opposite sides of similar groups. Cis is on the same side trans is on opposite sides

E/Z: same or opposite sides of the highest priority groups

What is crude oil?

A complex mixture of hydrocarbons mainly alkanes which may be straight-chain so unbranched or branched

Crude oil can be separated into fractions. What are these fractions of crude oil?

Groups of hydrocarbons with similar chain lengths and boiling points

Hydrocarbons with similar numbers of carbon atoms have different intermolecular forces. True or false?

False, they have the same intermolecular forces

What is a use of refinery gas?

Bottled gas

What is a use of gasoline?

You for cars

What is the use of kerosene?

Aircraft fuel

What is a use of diesel?

Fuel for lorries buses or cars

What is the use of Fuel oil?

Fuel for ships and power stations

What is a use of bitumen?

Used to surface roads and roofs

What is the separation of crude you called?

Fractional distillation

How is fractional distillation carried out?

Carried out in a fractionating column that is hot at the bottom and cool at the top

1. Describe the process of fractional distillation

1. Crude oil is heated so that most of it vaporises

. The vape is enter the fractionating column and rise upwards

. Hydrocarbons with high boiling points condense lower down in the column where the temperature is higher

.hydrocarbons with low boiling points rise further up before condensing

2. Smaller hydrocarbon molecules are collected near the top of the column often gases

3. Larger hydrocarbons are collected lower down

What happens when sulphur containing compounds in crude oil are burned?

They produce sulphur dioxide which contributes to acid rain

Is fractional distillation a physical or chemical process and why?

It is a physical not chemical process because intermolecular forces are broken, not covalent bonds

What are alkanes?

Hydrocarbons that can be produced by additional reaction of hydrogen to an alkene or by the cracking of longer alkane chains

What is cracking and why is it needed?

The conversion of low value surplus into high demand products. This is because the supply of long chain fractions exceed the demand while shorter chain alkanes/alkenes are more valuable.

What happens during cracking?

Large less useful hydrocarbon molecules found in crude oil are broken down into smaller more useful molecules

What type of reaction is cracking and what does it involve?

It is an endothermic reaction and it involves breaking carbon to carbon bonds in alkanes

1. Describe the process of cracking

1. The large hydrocarbon molecules are fed into a steel chamber and heated to high temperatures and then passed over a zeolite Or aluminosilicate catalyst

   → The chamber does not contain oxygen to prevent the combustion of the hydrocarbon to water and carbon dioxide

2. When the larger hydrocarbon is cracked, smaller alkane and alkenes are formed

What are the two types of cracking?

thermal cracking and catalytic cracking

What is the thermal cracking?

Requires high temperatures and high-pressure and produces alkanes and a lot of alkenes

What is catalytic cracking?

Uses a lower temperature and slight pressure in the presence of a catalyst such as zeolite or aluminosilicate to produce motor fuels and mainly aromatic hydrocarbons. Catalytic cracking breaks covalent bonds so is a chemical change

What is complete combustion?

When alkanes are banned in excess oxygen. All carbon atoms are oxidised to carbon dioxide and all hydrogen atoms are oxidised to water

Alkane+oxygen→carbon dioxide+water

What is incomplete combustion?

When alkanes burn in limited oxygen, The carbon is not fully oxidised

Instead of forming carbon dioxide, some carbon is partially oxidised to carbon monoxide

Alkane+oxygen→carbon monoxide+water

With a reduced supply of oxygen carbon will be produced in the form of soot

Alkane+oxygen→soot+water

Where does incomplete combustion usually take place and why?

Often takes place inside a car engine due to a limited amount of oxygen present

What is Carbon monoxide?

A toxic colourless and odourless gas

What are the effects of carbon monoxide and explain why?

Can cause dizziness, unconsciousness and in severe causes death

Carbon monoxide binds strongly to haemoglobin in red blood cells reducing its ability to bind and transport oxygen

Describe the reactions of oxide of nitrogen

In court engine, very high temperatures and pressures are reached

N2(g)+O2(g)→2NO(g)

The nitrogen monoxide can then be further oxidised and air

2NO(g)+O2(g)→2NO2(g)

Nitrogen oxide can also dissolve and react in water with oxygen to form nitric acid which is a cause of acid rain

What are the effects of acid rain?

Acid rain can cause corrosion of building, In danger plants and aquatic life and directly damage human health

Where are nitrogen oxide released from?

Released from car exhaust fumes into the atmosphere Car exhaust fumes also contain unburnt hydrocarbons which are volatile organic compounds

What do most modern cars have fitted to reduce the emission of harmful gases?

Catalytic converters

What type of metals are inserted into the catalytic converter and how they arranged?

Precious metals such as platinum Palladium and rhodium are coated onto a ceramic honeycomb structure

Why are the precious metals coated onto a ceramic honeycomb structure?

This provides a large surface area for the catalytic reactions to take place

Give the three main reactions in catalytic converters

How can sulphur dioxide emissions from coal fired power stations be reduced?

By treating the waste gases before they are released into the atmosphere

What is flue gas desulfurisation also known as?

Sulfur scrubbing

What is sulfur scrubbing?

Waste gases are passed through a scrubbing tower where a slurry containing calcium oxide or calcium carbonate sprayed into the gases

What happens when calcium oxide is used in sulphur scrubbing?

Calcium oxide reacts with sulphur dioxide and water to form calcium sulfite Which is an oxidised to calcium sulfate

CaO(s)+2H2O(l)+SO2(g)+1/2O2(g)→CaSO4.2H2O(s)

What happens when calcium carbonate is used in sulphur scrubbing?

It reacts with sulphur dioxide and oxygen to form calcium sulphate and carbon dioxide

CaCO3+1/2O2(g)+SO2(g)→CaSO4(s)+CO2(g)

This process removes sulphur dioxide from flue gases and reduces the formation of acid rain

Alkanes undergo free radical Substitution. What is this?

When A hydrogen atom is replaced by a halogen atom such as chlorine or bromine

What is required to initiate the reaction due to alkanes being relatively unreactive

UV light is used

Why are alkanes unreactive?

Because they are nonpolar meaning the carbon and hydrogen have very similar electronegativities and the bonds are strong so can’t be broken

What reaction does the UV light cause?

It causes a homolytic fission Of the halogen molecule forming free radicals that begin the substitution process

What is a free radical?

Any species with an unpaired electron

What are the three steps in free radical substitution?

Initiation step, Propagation step and termination step