C7 - Organic Chemistry

Compare structural formula with displayed formula (4maks):

• Structural does not show all the bonds

• Displayed shows which atoms are bonded to each atom

• Displayed shows type of covalent bond

• Both show correct number of atoms

how is crude oil made

Crude oil is formed over millions of years from the remains of plants and animals

What is crude oil

Crude oil is a mixture of hydrocarbons, it is a non renewable fossil fuel

Alkanes

• The series of saturated hydrocarbons - contains single C-C covalent bonds

• General formula for alkanes: C_nH_2n+2

complete combustion

combustion needs a plentiful supply of air so that the elements in the fuel react fully with oxygen

hydrocarbon + oxygen → (complete)

carbon dioxide + water

hydrocarbon + oxygen → (incomplete)

carbon monoxide + water + carbon (sut)

 

Short hydrocarbon properties

• Low boiling point

• Very flammable

• Gas at room temperature

• Low viscosity( not thick)

long hydrocarbon properties

• High boiling point

• Not flammable

• Thick liquid at room temperature

• High viscosity

how does chain length affect boiling point and viscosity

both increases

fractional distillation

1. The fractional column is hot at the bottom and cold at the top. crude oil is heated at 600 and vaporised and pumped into the fractionating column

2. Short chain hydrocarbons have low boiling points so rise and condenses higher up the column

3. Lon chain hydrocarbons have very high boiling points so condense lower down the column - fuel oils

4. All different chain lengths condense and are separated into their fractions

5. The longest hydrocarbons chains do not vaporise and are extracted as a viscous liquid called bitumen

Why is bitumen drained off as a viscous liquid during fraction distillation? (4)

It is a long chain hydrocarbon held together by strong intermolecular forces which gives it a higher boiling point so more energy is required to evaporate it.

boiling point of ethenol

78

levels of fracitonal destilation

1. petroleum gas

2. gasoline

3. keresone

4. diesol

5. residue

what is cracking

 When long chain hydrocarbons produced by fractional distillation are turned into smaller hydrocarbons.

we do this because they are more useful and in demand

what are the different types of cracking?

Catalytic cracking - vaporising the hydrocarbon and pass it over a catalyst

Steam cracking - mix it with steam, and heat to very high temperature the steam will break the hydrocarbon

what is a homologous series

a family of compounds that share the same functional group where each successive member differ by CH2

alkenes description

They contain a double carbon to carbon covalent bond

They are unsaturated hydrocarbons.

what is an isomer

 each of two or some compounds with the same formula but a different arrangement of atoms in the molecule and different properties

what is a functional group

an atom of group of atom the dictates the chemical behaviour

test for alkenes

Bromines water is brown it turns colourless when it is reacted with an alkene.

addition reaction

An organic reaction where two or more molecules combine to form a larger one. (one product)

what is saturated

 each carbon atom is bonded to the maximum number of atoms

are alkenes or alkanes more reactive?

Alkenes are more reactive than alkanes because alkenes are unsaturated therefore they can add additional atoms making them react more readily.

combustion of alkenes

Alkenes produce a smoky yellow flame when burnt

They release less energy when oxidises

aklene + steam →

alcohol

what is ethanol used as

fuels and solvents

ethanol + sodium

sodium ethoxide + hydrogen

what will happen when alcohol reacts with sodium

• The sodium will fizz and begin to dissolve

• Producing a strong alkali solution of sodium ethoxide

• Hydrogen gas is also produce

alchohol oxidation

• Alcohols can be oxidised through combustion

• They can be oxidised using an oxidizing agent

• turns from orange to green

• Ethanol + potassium dichromate -> ethanoic acid + water

• Potassium dichromate is an oxidizing agent

fermentation

glucose → ethanol + carbon dioxide ( with yeast )

uses of carboxylic acids

• food (vinegar)

• Soap production

• Medicine

They are good for this because they are weak acids

pH level trends for carboxylic acids

The pH levels of carboxylic acids increases the bigger the molecule e.g. Methanolic acid is more acidic than propanoic acid

3 advantages of make ethanol by hydrating ethene:

• Ethanol produced through hydration have higher purity

• Its more efficient because only one product is made therefore you don't have to separate them

• Continuance production therefore it is quicker to make.

• 100% atom economy

disadvantages of making ethanol by hydrating ethene (2)

• (more energy intensive) uses fossil fuels to heat up to 300^o

• Uses crude oil (non -renewable)

3 advantages of fermentation:

• Starting products is sugar and yeast which are cheap and easy to obtain and grow

• More environmentally friendly than the other method as you don't burn fossil fuels

• Uses renewable resources

disadvantages of fermentation

Uses enzymes therefore need optimum temperature

cant be continually produced

Carboxylic acid  + metal carbonate:

• Carboxylic acids from acidic solutions when they dissolve in water

• They react typically with metals the same way all acids do

• salt + water + carbon dioxide

carboxylic acid + metal carbonate →

salt + water + carbon dioxide

Ethanoic acid + sodium carbonate ->

 sodium ethanoate + water + carbon dioxide

esters

• Reversible reaction (yields can be increased by using pure substances)

• Uses sulphuric acid catalyst

• Esters are volatile (evaporate easily)

• Have fruity/sweet smells, used in perfumes or food flavouring

• ethale ethonoate

carboxylic acids + alcohol →

ester + water(condnsation reaction)

what are ester used for?

• Sweets - food flavouring

• Perfumes (fruity smell)

• Volatile liquids (low boiling point) and turn into vapor easily

polymers 

• Lots of small units (monomers) linked together to form a long molecule (polymer)

• Many ethene monomers will create polyethene

addition polymerisation

• Monomers break their double carbon bonds to form a singular bond polymer

• Like all addition reactions only one product is formed

 

properties of polymers depend on 

• The monomers that make them

• The conditions that polymers has been produced in

thermoforming polymers properties

• Soften easily

• Weak intermolecular forces

• Broken when heated

• Polymers can be reheated

thermosetting polymers properties

• Do not melt when heated

• Strong covalent bonds forming crosslinks between the polymer chain

• Strong covalent cross links between polymers prevents them from softening

consensation polymerisation

• Uses 2 different monomers (not alkenes) to produce a polymer and another small molecule

• Addition polymerisation -> additional polymer

• Condensation polymerisation -> condensation polymer + small molecule

how to form polyester

Monomer 1

• Ethanediol

• Containing 2 alcohol groups

• HO - CH2 - CH2 - OH

• Diol monomer

Monomer 2

• Hexanedioc acid

• Containing two carboxylic acid groups

• HOOC - CH2 - CH2 - CH2 - COOH

• Dicarboxylic acid monomer

monomer 1 + monomer 2 →

polyester + water

uses a ester link

condensation polymers properties

• Biodegradable - able to bread down naturally

• Microorganisms can break down the ester links

making nylon

must be in a fume cupboard

naturally occurring polymers (4)

• DNA

• Starch

• Cellulose

• Proteins

what are amino acids 2 functional groups:

 

Bases: called amine group - NH2

Acids: - called carboxylic acid - COOH

carbohydrates

 

Glucose monomer --> starch polymer + water

Glucose monomer --> cellulose polymer + water

 

how is it made? (DNA is known as polynucleotide)

millions of nucleotide → DNA + water