Chemistry Revision: Organic Chemistry

Organic Chemistry consists of molecules containing primarily carbon and hydrogen

A molecule containing only carbon and hydrogen is known as a hydrocarbon

Other common elements used in organic compounds are nitrogen, oxygen, and the halogens (Group 7)

WORTH MENTIONING: THE COMPOSITION OF AIR

78% Nitrogen, 20% Oxygen, 1% Carbon Dioxide, 1% other gases

Formula for calculating Hydrogen atoms: CnH(2n+2)

Example: CH4,C2H6, etc...

Isomers

Isomers have the same molecular formula but different arrangements in space (different structural formula)

Example: 

A homologous series is a series of organic compounds with a similar general formula

They possess similar chemical properties due to the presence of the same functional group

HOWEVER they have different chemical properties as a result of increase in mass and molecular size

EXAMPLE- Alkenes only have 1 double bond

Alkene formula=CnH2n

Alkane formula= CnH(2n+2) 

ALKENES ARE UNSATURATED (CAN MAKE MORE BONDS)

ALKANES ARE SATURATED (CAN NO LONGER MAKE BONDS)

Formation:

Millions of years ago dead marine animals and plants formed a layer of sediment on the sea bed. This layer was buried by a deposit of mud and rock fragments. Heat and pressure from the overlaying layers of rock decayed the organic matter in anaerobic conditions and formed a pocket of gas and oil, The gas and oil passed through the porous rock collected beneath layers of non-porous rock.

Conditions:

• Animal Remains
• HIGH Temperature
• HIGH Pressure
• Anaerobic conditions
• Millions of years

Extraction:
Drill through the inpermeable layer to release the oil which is then extracted by being pumped up to the surface. 

The oil is heated to about 400degrees until it vaporises and passes into a fractionating column.

The fractionating column has a temperature gradient, cooler towards the top.

As the vapour rises up the column, groups of alkanes reach a temperature cool enough to allow them to condense. The smaller alkanes condense towards the top of the column.

Each group of alkanes will condense within the column at a specific height which is determined by its boiling point.

The liquid alkanes are then topped off from the column in seperate fractions.

Polymers are long chain molecules, formed by reacting lots of short chain molecules, or monomers (e.g. alkenes), together

TEST FOR SATURATION: REACT BROMINE WATER WITH A HYDROCARBON:  IF THE BROMINE TURNS COLOURLESS, THEN THE REACTANT WAS UNSATURATED.

Polymerisation- Alkenes undergo this to form various plastics. It is the name of when monomers join together to form polymers.

The monomers MUST have a double bond, only alkenes will be used at GCSE.

Uses- Poly(e)thene=Shopping bags/buckets,Polypropene=Milk crates/Rope,Polystyrene=Packing/Insulation

INTERMOLECULAR FORCES- The strength of forces between polymer chains depends on:

• The monomer used
• Conditions chosen for polymerisation

THERMOSETTING POLYMERS AND THERMOSOFTENING POLYMERS

2 methods: FERMENTATION OF SUGARS and HYDRATION OF ETHENE

FERMENTATION OF SUGARS: 
Sugars dissolved in water>yeast added to the mixture>Mixture maintained between 30 and 40 degrees
Yeast produces enzymes, the biological catalysts. Sugars produce ethanol and carbon dioxide
Glucose=Ethanol + Carbon Dioxide (ANAEROBIC)

Advantages: Renewable, suitable for drink manufacture
Disadvantages: Batch process, takes longer, only 15% ethanol

HYDRATION OF ETHENE
Crude oil fractionally distilled>Fractions of alkanes cracked>Ethene + Small alkane hydrated>Ethanol

Advantages:Fast,Continuous,Suitable as fuel, almost pure ethanol
Disadvantages: Non-renewable, requires high temperature 

GENERAL FORMULA=RCOOH, WHERE R=THE FUNCTIONAL GROUP (WHAT MAKES THE CHAIN REACT IN A CERTAIN WAY)

METHANOIC ACID=HCOOH

ETHANOIC ACID=CH3COOH MAIN COMPONENT OF VINEGAR, WHEN REACTED WITH AN ACID FORMS A SALT AND WATER

REACTIONS OF ETHANOIC ACID WITH ALKALIS/CARBONATES + METALS FORMS ETHANOATE SALTS

IF CO2 IS RELEASED WITH A METAL CARBONATE OR METAL HYDROGEN METAL CARBONATE THEN THIS SHOWS THE PRESENCE OF CARBOXYLIC ACIDS.

FORMED BY WARMING ALCOHOLS WITH AN OXIDISING AGENT

FORMED BY THE REACTION OF CARBOXYLIC ACIDS WITH ALCOHOLS 

THE PREFIX OF THE NAME COMES FROM THE ALCOHOL GROUP

THE SUFFIX COMES FROM THE CARBOXYLIC ACID

EXAMPLE:

ETHANOIC ACID + METHANOL= METHYL ETHANOATE

CH3COOH