DF3: Hydrocarbons Flashcards
What is crude oil?
A thick black liquid consisting of a mixture of hydrocarbons
Explain the process of fractional distillation.(4)
- At the refinery, the crude oil is heated to vapourise it
- vapour passes into the distillation column
- Vapour rises up through the column, separating into different fractions
- as different ones condense into liquids and run off at different levels
Does density increase/decrease up a fractionating column?
Decrease
Does boiling point increase/decrease up a fractionating column?
Decrease
Does chain length increase/decrease up a fractionating column?
Decrease
Does volatility increase/decrease up a fractionating column?
Increase
Does flammability increase/decrease up a fractionating column?
Increase
Why does each fraction not have an exact boiling point?
Each one is a mixture of many different hydrocarbons
Why is organic chemistry named so?
Many carbon compounds are found in living organisms
What does organic chemistry include?
All carbon compounds except CO, CO2 and carbonates
How many electrons does carbon have in its outershell?
4
Why does carbon generally form covalent bonds?
If it achieved stability by becoming an ion it would be too highly charged (4+ or 4-)
What is catenation?
Carbon’s ability to form strong covalent bonds with itself to give chains and rings of itself
What does catenation lead to?
The limitless variety of organic compounds
Define “hydrocarbon”
Compounds containing only carbon or hydrogen
What is the general formula for hydrocarbons?
CxHy
Define “aromatic”
Compounds containing one/more benzene rings
Define “aliphatic”
Compounds not containing any benzene rings
Define “functional group”
Modifiers responsible for the characteristic chemical reactions of molecules
Define “saturated”
A compound with no bonds available for bonding
Define “unsaturated”
A compound containing bonds that can be broken open
Define “homologous series”
A series of compounds with the same general molecular formula
Are alkanes saturated?
Yes
How many bonds does carbon form?
4
Are alkanes aliphatic?
Yes
What is the general formula for alkanes?
CnH2n+2
Name the first ten alkanes
- Methane
- Ethane
- Propane
- Butane
- Pentane
- Hexane
- Heptane
- Octane
- Nonane
- Decane
What is the relationship between alkane chain length and tendency to become a solid and why?
As chain length increases, the tendency towards a solid also increases because the boiling point increases
What state are alkanes n= 1 - 4 in?
Colourless gases
What state are alkanes n=5 - 16 in?
Colourless liquids
What state are alkanes n=17+ in?
White waxy solids
Do alkanes mix well with water?
No they form two separate layers
Why do alkanes not mix well with water?
Water contains polar molecules that attract each other and prevent alkane molecules mixing with them
What are cycloalkanes?
A ring of carbon atoms with two hydrogens attached to each carbon
What is the general formula for alkanes?
CnH2n+2
Are cycloalkanes saturated?
Yes
Are alkenes saturated and why?
No - the carbon double bond can open up and bond with more hydrogens
What is the general formula for alkenes?
CnH2n
Are alkenes aliphatic?
Yes
What is the general formula for cycloalkenes?
CnH2n-2
Are cycloalkenes aliphatic?
Yes
Are cycloalkenes saturated?
No
What is the formula of benzene?
C6H6
How many carbons and double bonds does a benzene ring contain?
6 carbons and 3 double bonds
Why are benzene rings more stable (less reactive) than expected?
The double bond electrons are delocalised around the carbon ring, unattached to any particular carbon
Is benzene aliphatic?
No - aromatic
Is benzene saturated?
No
Is alcohol a hydrocarbon?
No
What is the general formula for alcohols?
CnH2n+1OH
What is the functional group for alcohols?
The hydroxl group (-OH) which can be attached to any carbon atom on the chain
What is a general formula?
A formula that can describe any member of a family of compounds
What is a molecular formula?
The actual number of atoms of each element in a molecule
What is the shortened structural formula?
A formula showing the atoms, carbon by carbon with the attached hydrogens and functional groups
What is the structural formula?
Shows how all the atoms are arranged and all the bonds between them
What is the skeletal formula?
Shows the bond between the carbon skeleton only, with any functional groups. The hydrogen and carbon atoms are not shown.
Why is giving systematic names important?
It allows for the full structural formula of a compound to be determined.
What is the formula of methyl?
CH3
What is the formula for all alkyls after methyl?
CH3 + CH2 for every carbon atom
What is the prefix for two identical sidechains?
Di
What is the prefix for three identical sidechains?
Tri
What is the prefix for four identical sidechains?
Tetra
