chemistry - topic 7 organic chemistry

What is crude oil?

• fossil fuel

• Liquid found in porous rocks

• Finite recourse

• Contains mixture of compounds e.g petroleum, diesel ct

How is crude oil formed?

• plankton and other small sea creatures die

• Sink to bottom of sea bed and buried by sediment for millions of years

• The heat, pressure and lack of oxygen causes them to turn into crude oil

What does crude oil consist of ?

hydrocarbons - different sized molecules with only hydrogen and carbon in them

What Are alkanes?

• most common type of hydrocarbon found in crude oil

• All end in -ane

General formula for alkanes?

Cn H2n + 2

2 times carbon number + 2

Names for all hydrocarbons?

1 carbon = meth

2 carbon = eth

3 carbon = prop

4 carbon = but

• all others follow same named as shapes

What is a fraction ?

Hydrocarbons can be split into fractions which are molecules that have similar number of carbon chains

What do fraction supply?

• fuels (e.g petrol and diesel)

• Feed stuck for petromechanical industry (raw ingredients to make something else)

Fractional distillation method?

• fractioning tower which is hot at bottom and cool at top

• Heated crude oil enters fractioning column

• Vapor’s from oil rise through column

• Vapours condense when they are cool enough

• Fractions leave at different heights based on boiling points

Properties of smaller hydrocarbon chains?

• more flammable

• More volatile

• Less viscose (thin)

Longer chain properties?

• less flammable

• Less volatile

• More viscous (thick)

Boiling point and hydrocarbons ?

Boiling point increases as the chain less increases

Hydrocarbon uses?

• bottom = bitumen (surfacing roads)

• Fuel oil (ships)

• Diesel (car / trains )

• Kerosene (planes)

• Petrol (cars)

• Top = refinery Gases (e.g methane for labs and kitchens )

Hydrocarbons and oxygen ?

Can be burnt with oxygen to release large amounts of energy

Complete combustion?

• good supply of oxygen

• Fuel + oxygen —> carbon dioxide and water

Incomplete combustion?

• poor supply of oxygen

• Fuel + limited oxygen —> carbon monoxide + water

Dangers of carbon monoxide

• toxic

• Binds to RBC + reduces body ability to transport oxygen

Cracking?

When you crack a large alkane you with get a smaller alkane and an alkene

What is an alkene?

• unsaturated hydro carbon

• Contains at least one double C=C bond

General formula for alkene?

• Cn H2n

Saturated?

• means full up

• AlKanes are saturated

• No other atoms can be added

• NO double bond

• Less reactive than alkenes

Test for alkenes?

• bromine water

• If present will go from orange to colourless

How to crack hydrocarbons ?

• pass over hot catalyst (catalyst put in)

• Mixed with steam + heated to a very high temperature

• Bonds broken, causes thermal decomposition to occur

Alkenes and oxygen ?

• often had a Smokey flame due to incomplete combustion

• E.g ethane + oxygen —> carbon dioxide + water

Alkenes + hydrogen ?

• all react with hydrogen as have double C=C bond, so don’t contain maximum number of hydrogen

• Double bond becomes single

• E.g ethane + hydrogen —> ethane

• Turn back into there alkane

• margarine made using pentene and hydrogen

Alkenes and water?

• reaction works be water atoms turning double bonds into single bonds

• Process makes alcohol

• OH is alcohol functional group

• E.g. ethane + steam —> ethanol

Alkenes + halogens?

• don’t contain maximum amount of atoms

• Halogen atoms added on to carbon , double bond to single bond

• Halogenalkanols

• E.g ethane + bromine —> dibromoethane

Alcohol general formula?

Cn H2n + 1 OH

E.g Methanol = CH3OH

Uses of alcohol?

• methanol = fuel, clothes, paint + pharmaceuticals

• Ethanol = alcoholic drinks, hand sanitizer

• Propanol = antifreeze, rubbing alcohol, hand sanitizer

• Butanol = solvent, varnishes and fuel

Alcohol + oxygen (combustion)

Methanol + oxygen—> carbon dioxide and water

Alcohols with water?

• short length alcohol are extremely soluble , mix very easily (e.g methanol, propanol)

• Longer chains are less soluble , two distinct layers form

Alcohol with sodium?

• add group one metal to alcohol, bubble of hydrogen gas produced , liquid contains sodium … oxide

• E.g. sodium + ethanol → sodium ethoxide + hydrogen

Alcohols with oxidising agent?

• oxidation is loss of electrons or gain or oxygen

• Represented as [o] - oxidising agent

• Must occur through distillation or reflux

• Oxidising alcohols form new compound called carboxylic acid (weak acids e.g citric acid, ethanoic acid (vineger), methanoic acid (bug bites)

• E.g propanol + oxidising agent → propanoic acid + water