Alkane

NCEA L1 Science 2013 Chem 1.3

Chemistry NCEA L1

1.3 Carbon Chemistry

Understand that matter, including carbon, is made up of particles /atoms

An atom is the smallest neutral particle that makes up matter.

The type of atom and the way these atoms are arranged and connected to each other determines the type of matter – and therefore the physical and chemical properties of the matter.


Atoms have a particular structure – protons, electrons and neutrons

Atoms have a central nucleus. The nucleus contains protons (p) and neutrons (n).

Electrons (e) orbit the nucleus, arranged in shells or energy levels.

Electron

-ve

Nucleus

P

N P

N

P

N

N

N

P

P

P

N

Neutron

Proton

+ve

This is known as the

Bohr model.


Shell 1

Shell 2

Carbon has four valence electrons. The electronegativity of carbon is too small for carbon to gain electrons from most elements to form C 4ions, and too large for carbon to lose electrons to form C 4+ ions. Carbon therefore forms covalent bonds with a large number of other elements, including the hydrogen, nitrogen, oxygen, phosphorus, and sulfur.

Groups of compounds in which the main atom in the molecule is carbon belong to a category known as organic

compounds.


Carbon chemistry

Covalent bonding between atoms

Covalent bonding occurs where valence electrons around atoms are shared between neighbouring atoms. This type of bonding is found between the C and H atoms in hydrocarbons and the C, H and O atoms in alcohol and is called intramolecular bonding. This bonding is very strong. The bonding between molecules is called intermolecular bonding and this is much weaker.

When hydrocarbons are heated and they change state into liquids and gases it is this bonding that is broken not the covalent bonding.

Note the distinction:

Intra-molecular Forces: the strong bonding forces within a molecule. i.e. the covalent bonds holding the molecule together.

Inter-molecular Forces: the weak bonding forces between molecules due to the attractions between partial charges.


Covalent bonding between atoms

Lewis diagram of CH

4

(methane)

Hydrogen electron

Carbon electron

H x x

H

C x x

H

H

Bonded pair

Lewis diagrams can be used to show how atoms are arranged in a molecule and which valence electrons are used in bonding. A bonding pair of electrons can also be shown as a line:


H

H C H

H

Organic chemistry formula

Molecular Formula – type and number of each atom.

i.e. Propane C

3

H

8

Structural Formula – placement of each atom.

Condensed Structural Formula

CH

3

-CH

2

-CH

3

Structural isomers are molecules with the same molecular formula but different structural formula.

How many ways can you draw C

6

H

14 ?


Alkanes

Compounds that contain only carbon and hydrogen are known as hydrocarbons. Those that contain as many hydrogen atoms as possible are said to be saturated. The saturated hydrocarbons are also known as alkanes.


H

H

C

H

H

C

H

H

C

H

H

C

H

H

H

H

C

H

H

H

C

C H

H

H

H

C H

Alkanes

Straight-chain hydrocarbons, in which the carbon atoms form a chain that runs from one end of the molecule to the other .i.e. butane

H

H

C

H

H

C

H

H

C

H

H

C

H

H

Alkanes also form branched structures. The smallest hydrocarbon in which a branch can occur has four carbon atoms. This compound has the same formula as butane (C

4

H

10

), but a different structure. Compounds with the same formula and different structure are called structural isomers.

generic formula

C

n

H

2n+2

H

H

C

H

H

H

C

C H

H

H

H

C H


Sources of Alkanes

Alkanes are found in petroleum (either crude oil or natural gas). They are formed by the anaerobic decomposition of marine plant and animal organisms. The main components in new Zealand natural gas are methane (one carbon alkanes) and carbon dioxide.

Crude oil is imported into New Zealand from other countries and contains a mixture of different hydrocarbons with different length carbon chains. The different chain length hydrocarbons are separated by a process called fractional

distillation as they have different boiling points.


Prefixes are used to name the longest carbon chain


Naming straight chain alkanes

Write the name of the alkane as –

1. Identify the longest C chain

2. Write the name

1. Prefix of long chain

2. -ane


Chemical properties of alkanes

1.

Non reactivity of alkanes (in relation to acids, alkalis, metals, water, because they are non-polar molecules).

2.

Low melting and boiling points – intermolecular forces are weak van der

Waal forces.

3.

Odour – hydrocarbons are volatile because they have weak intermolecular forces and they have characteristic smells.

4.

Do not conduct heat or electricity.

5.

As the C chain gets longer the hydrocarbons change from gas to liquid to solid.

6.

Combustion of alkanes. Alkanes are very good fuels. You must know the equations for complete and incomplete combustion. You must know that the products of combustion for both complete and incomplete combustion.

7.

Alkanes are non-polar so they are

not soluble in water


Alkane reactions -substitution

Alkanes are saturated molecules, that is that every carbon atom has the maximum amount of atoms bonded to it. If any other atoms are to be added to an alkane one atom must be removed first.

This reaction is known as a substitution reaction. For this reaction to proceed enough energy must be available to overcome the activation energy required to break the strong C-H bond. The available site can then be occupied by the provided atom. This energy may be provided by heat or UV light


Alkenes

Alkenes are known as unsaturated hydrocarbons. The carbons do not contain as many hydrogen atoms as possible because two or more carbons are joined by a double bond. Each carbon atom involved in the bond shares two of its valance electrons therefore four electrons (in two pairs) are involved in the covalent bond.


H

H

H

C C

H

H

H

C

C H

H

Alkenes

Functional Group – One double carbon-carbon bond C=C

A functional group is the part of the molecule responsible for reactions typical of the homologous series.

Alkene Nomenclature

Alkenes are named in a similar way to alkanes, but the longest continuous carbon chain is numbered to give the carbon atoms in the double bond the lowest possible

numbers.

The position of the double bond is given by the smaller number of the two carbon atoms involved.

After numbering the longest chain C1-C2=C3-C4, the compound is named 2-butene or but-2-ene, but not 3-butene nor but-3-ene .

H

H

C C

H

H

H

C

H

C

H

H

generic formula

C

n

H

2n


Write name as


2. Location of C=C

3. –ene

Naming alkenes

Number carbons so double bond has the lowest number.


Addition reactions

Alkenes are unsaturated molecules, that is that not every carbon atom has the maximum amount of atoms bonded to it because it has one or more double bonds. If another atom is added to an alkene the double bond can be broken down to a single bond and the available site can be occupied by another atom.

This reaction is known as an addition reaction. This reaction has a lower activation energy requirement than substitution, that is it requires less energy to break a double bond than break a C-H bond, therefore it can proceed easier than a substitution reaction.


Break this bond

Two places to bond atoms to

Addition reactions

Alkenes undergo addition reactions - this means they can undergo addition of a halogen atom (chlorine, bromine, iodine) across the double bond to form a haloalkane.

The common test for an unsaturated hydrocarbon (alkene) to distinghuish it from a saturated hydrocarbon (alkane) is therefore the rapid decolourisation of an orange solution of bromine. This occurs both in the presence or absence of sunlight compared with the slower decolourisation (only with uv light) of the alkanes.

CH

3

CH=CH

2

+ Br

2



1,2-dibromopropane


Tests to distinguish between Alkanes and Alkenes

We can use these to identify whether the molecule is an alkene or alkane

Alkane – single bonds, saturated hydrocarbon

Subsitution – one (or more) hydrogen replaced by another atom

Halogenation (Bromine)

Orange colour fades slowly in UV light

Acidified Potassium Permanganate

Doesn’t react – solution remains purple

Alkenes – at least one double bond, unsaturated hydrocarbon

Addition reaction – double bond breaks and atoms added

Halogenation (Bromine)

Orange colour disappears immediately changes to haloalkane

Acidified Potassium Permanganate

Purple to colourless – oxidation changes to alcohol


Alcohol

Alcohols are not considered hydrocarbons as they have one or more oxygen atoms attached in addition to the hydrogen and carbon atoms. Alcohols are organic substances however and share many of the same chemical and physical properties of the alkanes and alkenes. Alcohols are used as solvents and fuels and ethanol (a two carbon alcohol) is used as a drink.


Alcohol

Functional group is the hydroxyl group –OH (not a hydroxide )

Naming alcohols


2. an-

3. Location of OH

4. - ol


Alcohol properties

Small alcohol molecules are polar and the presence of the OH group means they are able to undergo intermolecular hydrogen bonding. The large difference in electronegativity (ability to “grab” electrons from another atom due to their pull from the combined positive protons in their nucleus) between the O and H atoms means the O-H bond is very polar and the slightly positive charge on this H atom is attracted to the non-bonding electron pairs of the oxygen on another molecule.

Physical properties: This means small alcohol molecules are highly soluble in

water. However as the length of the non-polar hydrocarbon chain increases this solubility in water decreases.

Chemical properties: Aqueous solutions are neutral. The presence of the OH group in this molecule is NOT the same as the OH- in sodium hydroxide,

NaOH (an ionic compound).


Summary of solubility in Water –Alkanes and Alkenes

Alkanes and Alkenes: Not soluble in water. These molecules are non-polar

(there is no negative or positive ends to the molecule) compared with water which is polar (having a negative area near the oxygen atom and positive area near the hydrogen atoms) so they are not attracted to each other. Alkanes and alkenes are immiscible (two or more liquids that will not mix together to form a single homogeneous substance) and form a distinct layer from the water.

Smaller C chained alkanes and alkenes are less dense than water and float on top.

If either an Alkane or Alkene is mixed into water eventually the two liquids will form separate

immiscible layers

Summary of solubility in Water –Alkanes and Alkenes

The less dense alkane floats on top of the water

Weak intermolecu lar bonds between alkane molecules

Hydrogen bonds between water molecules

Because attractions between water and alkane molecules are different from the water

– water and alkane – alkane attractions the two types of molecules stay separate

Alkanes and water do not mix.


Summary of solubility in Water - Alcohol

Alcohols: Soluble in water. These molecules are polar (due to the –OH end) and water, also being polar, will bond with the alcohol. The alcohol molecules will therefore disperse and mix within the water molecules.

At the instant ethanol and water are mixed the ethanol floats on top of the water

Because the attractions between their molecules are similar, the molecules mix freely, allowing each substance to disperse into the other

Hydrogen bonds between ethanol molecules.

Hydrogen bonds between water molecules.

Hydrogen bonds between ethanol and water molecules.

Ethanol and water mix.


Summary of Boiling points

Alkanes: The smaller the alkane molecule the lower the boiling point and the more volatile (easier to combust) the alkane. As the molar mass (Mass number of all the atoms combined) increases, the boiling points also increase as the strength of the intermolecular (between molecules) attractions increases.

The alkanes methane to butane (C1 – C4) are all gases at room temperature

Alkanes with between 5C and 15C atoms are all liquids

Alkanes with over 15 C atoms are soft solids

Alkenes: The boiling point trend is similar to alkanes where the larger the number of C atoms in the chain the higher the boiling point. The equivalent length C chain alkene has a slightly higher point than that of the alkanes.

Alcohols: The boiling point trend is similar to both alkanes and alkenes where the larger the number of C atoms in the chain the higher the boiling point.

The boiling point is higher than both alkanes and alkenes as the intermolecular bonding is stronger due to being a polar molecule– which creates a positive and negative end and hold the individual alcohol molecules together stronger and thus needs more energy to break them (heat energy)

Even small chain alcohols are liquid at room temperature



Summary of Boiling points

Addition polymers

Addition polymers are formed when alkene monomers undergo addition to form a polymer eg. polythene from ethene, P.V.C. from vinyl chloride

(chloroethene), polypropene from propene.

n(CH

3

CH=CH

2

)




H

H

C

H

C

H

C

H

Br

H

H

C

H

C

H

C

H

Br

H

H

C

H

C

H

C

H

Br

H

H

C

H

H

H

C

H

C

H

C Br H

H

H

C

H

C

H

C Br H

H

H

C

H

C

H

C Br

H

H

C

H

C

H

Br

–

Addition polymerisation

Monomers - smallest repeating unit with a double bond

Polymers – long chains of monomers joined together

Polymerisation – breaking of the double bond of each monomer and joining together with single bonds

MONOMERS

H

C

H

C

H

H

C

H

Br

H

C

H

C

H

H

C

H

Br polymerisation

H

H

C

H

H

POLYMER

H

C

H

C

H

C Br H

H

H

C

H

C

H

C Br H

H

H

C

H

C Br

H

H

C

H

C

H

C

H

Br

–

H

C

H

C

H

H

C

H

Br


Uses and importance of polymers from ethene and propene

The alkenes are used to make polymers (which we also refer to generally as plastics).

The chemical properties of these polymers such as low chemical reactivity with air, water and many chemicals make them ideal as containers for liquids and chemicals as they will not corrode or decompose. Polymers are also ideal as clothing that can be washed repeatedly.


Uses and importance of Polymers from ethene and propene

The physical properties of polymers such as their density (low) and strength make them ideal for strong yet light containers and clothing. Their ability to be melted and shaped makes production of moulded shapes efficient and cheap, as well as making polymers easy to recycle and reuse.

As polymers are insoluble in water they will not dissolve when exposed to water. Polymers are thermal and electrical insulators they have many uses in electrical applications, appliances and insulating wires.


Uses and importance of Polymers from ethene and propene

Examples:

Polythene, made from ethene, is very cheap and strong, and is easily molded. It is used to make, for example, plastic bags, bottles, and buckets.


Polypropene, made from propene, has strong fibers and a high elasticity. It is used, for example, in the manufacture of crates, ropes, and carpets

Combustion of Alkanes

Combustion of hydrocarbons involves the breaking of bonds between the

atoms, (as opposed to melting) either with plentiful oxygen – complete combustion, or limited oxygen – incomplete combustion. The products formed are water plus CO

2

(or CO/C with limited oxygen).


Combustion of Alkanes

Complete combustion

Alkane + Oxygen → Carbon Dioxide + water

Incomplete combustion

Alkane + limited oxygen → Carbon Monoxide or Soot + Water


Combustion

Complete combustion: needs plentiful O

2

The products are CO

2 and H

2

O

/ good ventilation. Flame burns clear / blue.

Energy efficient - maximum amount of energy in hydrocarbon released

Incomplete combustion: occurs in limited O

2

/ poor ventilation. Flame burns dirty yellow/orange. The products

CO and C (soot) and H

2

O.

Reduced energy efficiency – less than the maximum amount of energy in hydrocarbon is released complete incomplete

As C chain length increases you get more incomplete combustion occurring as bigger molecules need more O

2 complete combustion from


Combustion equations

Combustion Equations

Step 1. Write down the molecular formula of the alkane plus O

2 on the left hand side

Step 2. Write down CO

2 plus H

2

O on the right hand side

Step 3. Add the number of carbon atoms in the Alkane and balance the number of CO

2

(same as number of Cs)

Step 4. Add number of Hydrogen atoms in the Alkane and balance the number of H

2

(will be half number of Os)

O

Step 5. add the total number of Os on the RHS and balance the LHS of O

2 uneven number then you can use ½ Os)

(if there is an

Incomplete combustion

For limited oxygen replace CO

2 with CO and use same steps

For very limited oxygen replace CO

2 with C and use same steps


38

Combustion of Alcohol

Combustion

Complete Alcohol + 1

1/2

Oxygen CO

2

+ 2H

2

O

Incomplete Alcohol + 1 Oxygen CO + 2H

2

O

The longer the chain of carbons in the alcohol the less vigorously the combustion reaction. Methanol and ethanol (drinking alcohol) combust more readily.

Chefs will flambé a dish, setting alight the alcohol – this will reduce the alcohol content in the food or drink.


Combustion summary

Complete combustion – plentiful supply of Oxygen (CO

2

+ H

2

O)

Alkane C

3

H

8

+ 5O

2

3CO

2

+ 4H

2

O

Alkene C

3

H

6

+ 4

1/2

O

2

Alcohol C

2

H

6

O + 3 O

2

3CO

2

+ 3H

2

O

2CO

2

+ 3H

2

O

Incomplete combustion – limited supply (CO + H

2

O)

Alkane C

3

H

8

+ 3

1/2

O

2

3CO + 4H

2

O

Incomplete combustion – very limited supply (C + H

2

O)

Alkane C

3

H

8

+ 2O

2

3C + 4H

2

O

>Balance Carbon and Hydrogen on RHS

>Add oxygen to make CO

2

/CO/C and H

2

O on RHS

>Balance Oxygen by adding number of O

2 to LHS


Summary of reactions

Effects of Combustion products on human health and the environment

Carbon Dioxide

Increased levels of Carbon dioxide are linked to an enhanced greenhouse effect and global warming leading to climate change.

Climate change has resulted in melting polar ice and less settled weather as well as causing different climates that is affecting animal and plant survival.


Carbon dioxide is a greenhouse gas and traps heat in the atmosphere.

Without it and other greenhouse gases, Earth would be a frozen world

Earth’s climate in 4.5 billion-year has naturally changed between being very cold and covered in ice, or very hot. In the recent 10,000 years the planet’s climate has become much more stable, creating an ideal environment for humans and domestication of plants and animals.

However, over the past 50-100 years, increasing human activity (such as industry, agriculture and transportation) has begun to affect the natural climate balance. These activities are increasing the amount of greenhouse gases in our atmosphere and causing

Earth to heat up faster than ever seen before since humans have been on Earth.

43

Human activity is increasing the CO2 in the atmosphere and Earth is becoming a warmer place

Around 1750, the period of history called the industrial

revolution, humans began to burn (combust) fossil fuels and produce carbon dioxide in increasing amounts. The overall effect of human activities on the climate has been a warming influence.

According to scientific studies, in the past 650,000 years the planet has never had so much carbon dioxide in its atmosphere as it does today, and the levels of the gas are continuing to rise.


44


Human activity is accelerating climate change

Persistent human activities like driving cars, farming and burning coal in combustion reactions produce greenhouse gases – mainly carbon dioxide. This gas gathers in the atmosphere, wrap around the earth and trap the sun's heat.

45

Human activity is increasing the CO2 in the atmosphere and Earth is becoming a warmer place

The carbon dioxide and other greenhouse gases in the atmosphere act as an

“insulation blanket”. With not enough greenhouse gases the heat from the

Sun would reach Earth but then radiate away leaving the planet to cold. With too much greenhouse gases the heat is trapped around Earth and doesn’t escape as easily making the Earth to hot.

46



47

The more greenhouse gases we release, the faster the world's climate heats up. This process is called global warming but it also leads to climate change because it is increasing the amount of floods, storms, cyclones, droughts and landslips.

Climate change is affecting our economy, environment and the way we live – we are already seeing the effects and need to prepare for more changes in the future.


In New Zealand likely climate change impacts include: higher temperatures, more droughts in some areas and floods in others, and a change in the amount of rain with higher rainfall in the west and less in the east.

These changes in climate will cause a range of effects including changing agricultural productivity where some species will not grow as well and other warm loving species will need to be grown, warmer winters with fewer frosts, but hotter summers causing heat stress and diseases in plants and animals, rising sea levels will effect coastal areas and glaciers are expected to retreat.


48

All living things are made of carbon and that carbon changes from one form to another in a carbon cycle

Carbon exists in a number of forms. It is part of a gas molecule called

carbon dioxide found in the atmosphere which can be turned into carbon compounds in plants through

photosynthesis. This carbon is then passed along to other living organisms when they are consumed and released back into the atmosphere during respiration and combustion


49

All living things are made of carbon and that carbon changes from one form to another in a carbon cycle

Natural processes of photosynthesis and respiration (blue arrows) keep the carbon dioxide levels reasonably stable in the atmosphere – and therefore the global temperature steady.

Human activity such as farming, industry and burning fossil fuels (red arrows) which have a large amount of “locked up” carbon are affecting this balance and causing the levels of

Carbon Dioxide to increase.

50

Carbon can be stored in the Earth in ‘carbon sinks’ such as fossil fuels, rocks and ocean sediments

51



Carbon Monoxide

Carbon Monoxide (CO) is a colourless, odourless, toxic gas that is produced during incomplete combustion when not enough oxygen is available.

Carbon Monoxide stops haemoglobin in red blood cells carrying oxygen around body and so a person suffocates.



Carbon Monoxide



Soot (carbon)


Soot (C) is dirty and polluting.

Soot is produced during combustion when there is very limited amounts of oxygen available. Carbon particles can cause asthma in some people and even lung cancer.

Fuels

Fuels are a group of chemicals, mostly alkanes but also alkenes and alcohols, that humans use by converting the chemical energy stored in the high energy bonds between carbon and hydrogen into heat and light energy through the process of combustion. Fuels are used to heat homes and include coal and oil as well as for transportation and industry using oil, petrol, diesel and coal. Other fuels are processed into plastics.


The Earth has a fixed amount of resources that have to be managed sustainably

Sustainable means to continue being able to do something or use something indefinitely.

Some of our fuels on Earth are

Non-renewable such as coal, and oil and they will be all used up eventually as the process to make more takes a very long time. Other fuels such as biofuels are

renewable. As long as we do not take to much and replace what we use then these resources can be used for a long period of time sustainably.

57



Biomass energy

58

Biomass relies on the photosynthetic ability of plants to convert solar energy into chemical energy. The chemical energy stored in plants is then broken down by

enzymes and useful

bacteria into biofuels to be used in machinery.

This type of fuel is renewable as long as the same amount of trees are planted to replace those cut down. The carbon dioxide released when burning the fuels will also be reabsorbed by the plants as they grow.

Non renewable energy is energy that comes from the ground and is able to be not replaced within a useful period of time. Fossil fuels are the main category of non renewable energy.

Fossil fuels include; coal, oil and natural gas. These resources come from animals and plants that have died millions of years ago and then decomposed to create a useable source of energy for humans.

Non-Renewable Energy


59

Fossil Fuels - Coal

Coal was formed millions of years ago when plants fell into peat swamps and were buried by heavy earth and rocks. Over millions of years, the weight of the rocks and heat in the ground turned the plants into coal.

Most of the world’s coal was formed 300–350 million years ago during the

Carboniferous period that was warm and damp, ideal for plant growth. New Zealand coals are much younger – they were made 30–70 million years ago and they are a less energy rich fuel. Coal is mined either underground or in large open cast mines.

60

Fossil Fuels – Oil and Gas

Oil and gas were formed many millions of years ago from dead sea organisms falling to the sea floor and being covered by sediment. Over time the and formed rock. The carbon and hydrogen atoms that used to be part of the dead organisms bodies reformed into fuel – the liquid form called oil and the gas form. Oil and gas are mined by drilling deep into the ground from oil rigs.

The limits of fossil fuels and the unlimited energy of the sun

Fossil fuels are a limited resource. Extraction and mining can be expensive and can damage the surrounding area. Carbon dioxide gas that is released upon burning the fuels are contributing to the warming of the climate. Human society has a dependence on fossil fuels for energy but needs to consider alternative renewable energy sources to replace decreasing coal, gas and oil supply. Renewable energy is sustainable and in many cases produces little or no harm to the environment. As new technology develops to collect the energy it will become cheaper.

Fossil fuels

Renewable energy

62


Production of fuels – New Zealand Fuels

A fully laden coal train about to leave Seddonville for Westport. (1898)

Due to new Zealand’s geological history and the processes involved to create fossil fuels we do not have large fields of crude oil (unprocessed oil) but we do have sources of coal (but not the very black and old high energy coal) and natural gas (mostly methane).

Coal can be used directly by combusting it in power stations such as Huntly to heat water into steam and power turbines. It is also used in homes for heating. Combusting and mining coal is very polluting and its use is becoming more limited in New Zealand. Recent disasters (pike river) in coal mining have also reflected badly on the coal mining industry.

Production of fuels – New Zealand Fuels

Natural gas is extracted at fields around New Zealand, mostly off the coast out at sea, and this can be further processed into methanol (an alcohol fuel).

We can also produce Ethanol (an alcohol fuel) through the process of fermentation – anaerobic respiration of yeast.


Above: Kupe Gas platform in Taranaki

Methanol from Natural gas

Producing methanol (an alcohol CH

3

OH) from

Natural gas (an alkane CH

4

) is a three step process.

(i) Steam reforming where methane reacts with steam

CH

4

+ H

2

O → CO + 3H

2

(ii) Water shift reaction – a reaction that adjusts the ratio of CO: H

2 gas

(iii) Synthesis reaction

2H

2

+ CO → CH

3

OH

Methanol is used to make other chemicals that are used in making paints, plastics and explosives and in methylated sprits


Fermentation to produce fuel (ethanol)

Fermentation is anaerobic respiration. Enzymes in yeast turn sugar solution (eg glucose) into ethanol and carbon dioxide (in the absence of oxygen).

C

6

H

12

O

6

→ CO

2

+ CH

3

CH

2

OH

Glucose carbon dioxide ethanol


Production of fuels – imported Fuels

New Zealand needs to import crude oil from other countries and then further refine it (or process it) into other types such as petrol, diesel and motor oil in order to provide fuel for our cars, trucks and industries.

These processes of refining include fractional

distillation to separate out the mixed length carbon chain alkanes into distinct types of fuel as well as

cracking which breaks the long carbon chained alkanes into shorter, more useful fuels.


Fractional distillation of crude oil

Fractional column

Coolest at the top, gases

(Carbon chains 1 – 4) collected at the top – they have the lowest boiling points which is why they don’t condense – they stay as gases

Cooler as you go up, smaller molecules condense higher up as they have lower boiling points

Hottest at bottom. Large molecules condense here as have highest boiling points


Fractional distillation of crude oil

Different hydrocarbons and their boiling points

Petroleum Gas - Used for heating, cooking, and making plastics

-small alkanes (1 to 4 carbon atoms)

-commonly known by the names methane, ethane, propane, butane

-boiling range = less than 104 degrees Fahrenheit / 40 degrees Celsius

-often liquified under pressure to create LPG (liquified petroleum gas)

Naphtha - intermediate that will be further processed to make gasoline

-mix of 5 to 9 carbon atom alkanes

-boiling range = 140 to 212 degrees Fahrenheit / 60 to 100 degrees

Celsius

Gasoline - motor fuel

-liquid

-mix of alkanes and cycloalkanes (5 to 12 carbon atoms)

-boiling range = 104 to 401 degrees Fahrenheit / 40 to 205 degrees Celsius *

Kerosene - fuel for jet engines and tractors; starting materials for making other products

-liquid

-mix of alkanes (10 to 18 carbons) and aromatics



Different hydrocarbons and their boiling points

Gas oil - used for diesel fuel and heating oil; starting material for making other products

-liquid

-alkanes containing 12 or more carbon atoms


Lubricating oil - used for motor oil, grease, other lubricants

-liquid

-long chain (20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics


Heavy gas or fuel oil - used for industrial fuel; starting material for other products

-liquid

-long chain (20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics


Residuals - coke, asphalt, tar, waxes; starting material for other products

-solid

-multiple-ringed compounds with 70 or more carbon atoms

-boiling range = greater than 1112 degrees Fahrenheit / 600 degrees Celsius

Cracking of fractions

The cracking process uses heat and/or catalyst to break long less useful alkenes e.g. naptha fraction, into smaller more useful ones such as to make petrol or to make ethene (that can be made into plastics)

Temp, pressure, catalyst

C

10

H

22

--------------------- C

8

H

18

+ C

2

H

4

Long hydrocarbon chain alkane + alkene


Alkane

Chemistry NCEA L1

1.3 Carbon Chemistry

Molecular Formula – type and number of each atom.

i.e. Propane C

H

Structural Formula – placement of each atom.

Condensed Structural Formula

CH

-CH

-CH

Structural isomers are molecules with the same molecular formula but different structural formula.

How many ways can you draw C

H

generic formula

C

H

generic formula

C

H

Fossil fuels

Renewable energy

Related documents

Products

Support

Alkane

Chemistry NCEA L1

1.3 Carbon Chemistry

Molecular Formula – type and number of each atom.

i.e. Propane C

H

Structural Formula – placement of each atom.

Condensed Structural Formula

CH

-CH

-CH

Structural isomers are molecules with the same molecular formula but different structural formula.

How many ways can you draw C

H

generic formula

C

H

generic formula

C

H

Fossil fuels

Renewable energy

Related documents

Add this document to collection(s)

Add this document to saved

Suggest us how to improve StudyLib