Organic Chemistry Flashcards
What is a hydrocarbon
Any compound that is formed fr9m hydrogen and carbon atoms only
What is an alkane
The simplest type of hydrocarbon.
Alkanes are a homologous series - a group of organic compounds that react in a similar way.
Saturated compounds- each carbon atoms forms 4 single covalent bonds.
Name the first 4 alkanes
Methane
Ethane
Propane
Butane
What is the general formula of an alkane
CnH2n+2
Properties of short hydrocarbons
More runny
Less viscous
More volatile
Equation for complete combustion
Hydrogen + oxygen»_space;» carbon dioxide + water
During combustion what is oxidised
Carbon and hydrogen
Why are hydrocarbons used as fuels
The amount of energy released when they combust completely
How is crude oil made
Formed from the remains of plants and animals (mainly plankton) that are buried under sediment Over millions of years high temp and pressure causes the remains to turn to crude oil which is drilled up from rocks when found
How can crude oil be separated
Fractional distillation
How does fractional distillation work
- Oil heated till most of it turns into a gas. The gas enters the fractional column
- In the column it is hotter at the bottom and cooler as you go up
- Longer hydrocarbons have high boiling point. They condense back to liquids and drain out the column early on when they’re near the bottom.
What is cracking
Splitting up long chain hydrocarbons
What does cracking produce
Alkenes
What is an alkene
They are used as a starting material when making lots of other compounds and can be used to make polymers
How do you do cracking
- Heat long chain hydrocarbons to vaporise them.
- Then the vapour is passed over hot powdered aluminium oxide catalyst.
- The long chain molecule split apart on the surface of the specks of catalyst.
- CATALYTIC CRACKING
You can also crack hydrocarbons if you vaporize them, mix them with steam and then heat them to a her hugh temperature.
-STEAM CRACKING
Properties or alkenes
Double carbon bond
2 fewer carbon atoms compared to alkanes
Unsaturated
More reactive than alkanes
First four alkenes
Ethene
Propene
Butene
Pentene
Alkenes + addition reactions
The carbon double bond will open up to leave a single bond and a new atom is added to each carbon
Alkenes + hydrogen
Hydrogenation
Open up double bond carbons and form equivalent saturated alkanes.
The alkene is reacted with hydrogen in the presence of a catalyst
Alkenes + steam
Produce alcohol
Water is added across the double bond
The alcohol can be purified from the mixture by fractional distillation
Alkenes + halogens
Molecules formed are saturated within the double carbon bond each becoming bonded to a halogen atom
What is a polymer
Long molecules formed when lots of small molecules called monomers join together
How polymers are made
- Lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains. This is called additional polymerisation.
- When monomers react in additional polymerization reactions the only product is the polymer so an additional polymer contains exactly the same type and number of atoms as the monomers that formed it
General formula of an alcohol
Cnh2n+1OH
Properties of alcohols
Flammable React with sodium Can be oxidised by reacting it with oxygen Produce carboxylic acids E.g. methanol >>> methanoic acid
What is a carboxylic acid
A homologous series of compounds that all have -COOH as a functional group
What is am ester
Functional group -COO-
Formed from an alcohol and carboxylic acid
An acid catalyst is usually used
Condensation polymerisation
Monomers react together and bonds form between them making polymer chains.
For each new bond formed, a small molecule is lost
Amino acids
Contain two functional groups :
An amino group (NH2)
An acidic carboxyl group (COOH)
Polypeptides
The amino group can react with the acid group of another to form a polymer chain. For every new bond that is formed, a molecule of water is lost
