Organic AS Flashcards
What is the empirical formula
Empirical formula shows the simplest whole number ratio of elements within a molecule.
What is the molecular formula
Molecular formula shows the actual number of atoms of each element in a molecule
What does the structural formula show
Structural formula shows how the atoms are arranged in a molecule
What does the displayed formula show
Displayed formula shows a drawing of the arrangement of atoms in a molecule
ALL bonds must be shown
What does the skeletal formula show
Skeletal formula shows the carbon backbone and functional groups within molecules, no carbon-hydrogen bonds are shown
What are alkanes
Alkanes have single bonds between each carbon atom, all other available bonds are made to hydrogen atoms – they are called ‘saturated’ hydrocarbons
What are alkenes
Alkenes have a double bond between two of their carbon atoms – they are called ‘unsaturated’ hydrocarbons
What are alkly groups
Alkly groups are carbon chain groups bonded to another carbon chain
- CH3- methyl
- CH2CH3- ethyl
СН2СН2СН3-propyl
-СН2СН2СН2СН3-butyl
follows the same prefix as usual.
What does the functional group do
The functional group of a molecule dictates its chemistry, and its presence enables us to predict how the molecule is likely to react
What are structural isomers
Molecules that have the same molecular formula but different structures are called structural isomers.
What differs between chain isomers
They have different carbon chain arrangements to one another
What is Positional Isomerism
Where molecules that have the same molecular formula but have their functional group in different places
What are the steps to naming organic molecules
- When naming a compound, the length of the longest carbon chain must be determined. Use the prefix as for an alkane (meth, eth, prop…etc.).
- Alkyl and functional groups must be identified. Use the appropriate suffix (or prefix for halogenoalkanes) (-ol, -al, -oic acid, -yl for alkyl groups.).
- If a positional isomer is possible, the carbons in the chain must be numbered. The chain is always numbered, so a functional group or alkyl group is bonded to the lowest carbon number possible.
- When molecules contain two or more functional or alkyl groups, they are placed in alphabetical order.
- When numbering the other of priority is as so..
Halogens (lowest priority)
Alkyl groups
Alkenes
Other functional groups→ Highest priority
What is mean by a homologous series
“A series of chemically similar compounds which conform to a general molecular formula(same general formula)
Chemically similar or react in the same way .
• Each member of the series differs from the next by CH2
the members of the series show a graduation in physical properties.
• The length of the carbon chain has little effect on the chemical reactivity of the functional group
• The length of the carbon chain affects the physical properties (melting, boiling and solubility)
As the length of the carbon chain increases the melting point/boiling point increase because the intermolecular forces increase.
- Chain branching reduces melting points because the molecules pack together less well
What do isomers all have in common
Same molecular formula
What is a hydrocarbon
Something that contains carbon and hydrogen only
What is meant by the term saturated
Only single bonds present
What is meant by the term unsaturated
Contains double bonds (c=c)
Explain what happens in fractional distillation.
- crude oil is heated and enters the column as a vapour
- the vapour rises up the column, cooling as it does so
- crude oil is a mixture of alkanes with varying chain lengths and boiling points
- the different alkanes (fractions) condense at their boiling point and so will condense at different levels
- the fractions can then be pumped away separately
Why do we use cracking
Longer carbon chains are not very useful, therefore they are broken down to form smaller, more useful molecules. So we can make MORE PROFITS!
Explain the process of catalytic cracking
This method produces aromatic compounds with carbon rings. Lower temperatures around 720 K are used along with normal pressure, but a zeolite catalyst is needed to compensate for these less harsh conditions.
Explain the process of thermal cracking.
This method produces a high proportion of alkanes and alkenes. High temperatures around 1200 K and pressures around 7000 kPa are used to crack the carbon chains.
What is cracking .
Cracking is braking long chin alkanes into shorter alkanes and a alkene
Explain complete combustion of alkanes
When you burn (oxidise) alkanes (and other hydrocarbons)with plenty of oxygen you get only CO2 and H2O