organic chemistry

What do hydrocarbons contain?

Hydrogen and carbon

What are alkanes?

A single c-c bond

CnH2n+2

A homologous series

Saturated compounds

What is a homologous series?

A group of organic compounds that react in a similar way

What are saturated compounds in an alkane?

Each carbon atom forms four single covalent bonds

What happens to the properties of hydrocarbons as they get longer?

They change

Shorter- more runny, more volatile (lower boiling points) and more flammable

What is complete combustion?

Occurs when there’s plenty of oxygen

Releases lots of energy

Only waste products are carbon dioxide and water vapour

Hydrocarbon + oxygen = carbon dioxide + water

Both carbon and hydrogen are oxidised

Used as fuels due to amount of energy released

What is crude oil?

Made over long period of time

Formed from dead plants and animals

High temp and pressure causes them to turn to crude oil

Finite resource (non-renewable)

What is fractional distillation?

Crude oil made up of different hydrocarbons

Can be separated using fractional distillation

• oil is heated until most is gas - gases enter fractionating column

• In column is a temperature gradient

• Longer hydrocarbons have high boiling points - condense back into liquids and drain out early on

• Shorter hydrocarbons have low boiling points- condense and drain later on

  separate out into different fractions

What are different fractions of crude oil?

LPG- 3 carbons

Petrol- 8 carbons

Kerosene- 15 carbons

Diesel oil- 20 carbons

Heavy fuel oil- 40 carbons

What are the uses of crude oil?

Fuel for transport

Used as feedstock to make new compounds for things like polymers, solvents, lubricants and detergents

All examples of organic compounds

What is cracking?

Splitting up long chain hydrocarbons

Short chain hydrocarbons are flammable so make good fuels and are in high demand

Long chain form gloopy liquids which aren’t useful

Lot of alkane molecules produced from fractional distillation are turned into smaller, more useful ones by cracking

Cracking also produces alkenes

What is the method for cracking?

Thermal decomposition reaction (breaking molecules down by heating them)

Heat long chain hydrocarbons to vaporise them

Vapour is passed over a hot powdered aluminium oxide catalyst

The long chain molecules split apart on the surface of the catalyst- catalytic cracking

Also, vaporise, mix them with steam and then heat to high temp- steam cracking

What are alkenes?

Unsaturated

Have a double c=c bond

Double c=c double bond can open up to make a single bond

Alkenes are reactive

CnH2n

What combustion do alkenes generally undergo?

Incomplete combustion

Carbon dioxide and water are still produced, but also get carbon and carbon monoxide

Alkene+ oxygen = carbon + carbon monoxide+ carbon dioxide + water

Results in a smoky yellow flame

Less energy is released

How do alkenes react?

Addition reactions

The carbon double bond will open up to leave a single bond and a new atom is added to each carbon

what are examples of addition reactions with alkenes?

addition of hydrogen is hydrogenation

Forms the equivalent saturated alkane

In presence of catalyst

Steam reacts to form alcohols

Halogens also react

Eg bromine and ethene form dibromoethane

How can bromine test for alkenes?

Orange bromine water is added to a saturated compound no reaction = remain orange

If added to an alkene colourless solution

What are polymers?

Long molecules formed by lots of small molecules called monomers join together

Called polymerisation

Requires high pressure and a catalyst

Eg plastics made up of polymers

What are addition polymers?

Made from unsaturated monomers

Monomers that make up addition polymers have a double covalent bond

Unsaturated monomer molecules can open up double bonds and join together to form polymer chains - addition polymerisation

When the monomers react, the only product is the polymer so contains same number of atoms

What are alcohols?

-OH functional group

CnH2n+1

First four have similar properties

-flammable undergo complete combustion

All soluble in water - neutral pH

Also react with sodium

Can be oxidised to produce carboxylic acid

What are alcohols used for?

Solvents and fuels

Because they can dissolve most things that water can as well as can’t

How can ethanol be made?

Fermentation

Uses enzyme in yeast to convert sugars into ethanol

Carbon dioxide also producesd

Reaction occurs in solution so the ethanol produces is aqueous

Sugar= ethanol + carbon dioxide

Happens fastest at 37 degrees and slightly acidic solution and under anaerobic condition

What are carboxylic acids?

Functional group -COOH

End in anoic

How do carboxylic acids react?

React with carbonates to produce salt, water and carbon dioxide

Salts formed end in anoate

Can dissolve in water

When dissolved, they ionise and release H+ ions = acidic solution

Don’t ionise completely so weak acid

What are esters?

Made from carboxylic acids and alcohols

Functional group -COO

Acid catalyst usually used

Alcohol+ carboxylic acid= ester + water

What is condensation polymerisation?

Polymers can be made from condensation polymerisation

Involves monomers that contain different functional groups

Monomers react together and bonds form, making polymer chains

For each new bond, a small molecule is lost eg water

What are amino acids?

Contain amino group and carboxyl group

NH2 and COOH

Eg glycine

What are proteins?

Polymers of amino acids

Amino acids can form polymers (polypeptides) via condensation polymerisation

One or more long chains of polypeptides are known as proteins.

What is DNA?

Made from nucleotide polymer

Double helix structure

Made of two polymer chains of monomers called nucleotides

Nucleotides each contain a small molecule known as base - four types - A,C,G,T

Bases on different polymer chains pair up with each other and form cross links - creates double helix

Order of bases acts as code for genes

What are simple sugars?

Sugars are small molecules that contain carbon, oxygen and hydrogen

Reacts together through polymerisation to form larger carbohydrate polymers eg starch

Polymers