AS LEVEL CHEMISTRY ALKANES
Alkanes are saturated hydrocarbons.
They contain only carbon-carbon and carbon-hydrogen single bonds.
They are the least reactive of the organic compounds.
The main source is crude oil.
Hydrocarbon- a compound consisting only of hydrogen and carbon
Saturated- Contain single carbon -carbon bonds only
Unsaturated-contains a C=C bond
Petroleum fraction- mixture of hydrocarbons with a similar chain length and boiling range
The general formula for is CnH2n+2 (for ring alkanes is CnH2n)
Physical properties
Polarity
They are almost non-polar because the electronegitivities of carbon(2.5) and hydrogen(2.1) are so similar.
The only intermolecular forces between their are weak. However the larger the molecule the stronger the Van der Waals forces ) .
Boiling points
Because of the increasing intermolecular forces the boiling points of alkanes increase as the length of the carbon chain increases.
Alkanes with branched chains have lower melting points because they cannot pack together as closely and the van der waals forces are not as effective.
Solubility
Alkanes are insoluble in water
Water molecules are held together by hydrogen bongs which are much stronger than the van der waals forces in the the alkane molecule.
However they do mix well with other relatively non-polar liquids.
Reactivity
The are relatively unreactive. Due to strong carbon-carbon and carbon-hydrogen bonds.
They do not react with acids, bases, oxidizing and reducing agents.
They do burn and react with halogens under certain conditions.
Fractional distillation of crude oil
This is a Physical Process that includes the splitting of Van der Waals forces
Petroleum is a mixture mainly of alkane hydrocarbons
The process The crude oil is pre-heated in a furnace the mixture of liquid and vapor passes into a column
The fractions condense at different heights
The temperature of the column is cooler at the top than it is at the bottom
The separation depends on boiling point
They contain only carbon-carbon and carbon-hydrogen single bonds.
They are the least reactive of the organic compounds.
The main source is crude oil.
Hydrocarbon- a compound consisting only of hydrogen and carbon
Saturated- Contain single carbon -carbon bonds only
Unsaturated-contains a C=C bond
Petroleum fraction- mixture of hydrocarbons with a similar chain length and boiling range
The general formula for is CnH2n+2 (for ring alkanes is CnH2n)
Physical properties
Polarity
They are almost non-polar because the electronegitivities of carbon(2.5) and hydrogen(2.1) are so similar.
The only intermolecular forces between their are weak. However the larger the molecule the stronger the Van der Waals forces ) .
Boiling points
Because of the increasing intermolecular forces the boiling points of alkanes increase as the length of the carbon chain increases.
Alkanes with branched chains have lower melting points because they cannot pack together as closely and the van der waals forces are not as effective.
Solubility
Alkanes are insoluble in water
Water molecules are held together by hydrogen bongs which are much stronger than the van der waals forces in the the alkane molecule.
However they do mix well with other relatively non-polar liquids.
Reactivity
The are relatively unreactive. Due to strong carbon-carbon and carbon-hydrogen bonds.
They do not react with acids, bases, oxidizing and reducing agents.
They do burn and react with halogens under certain conditions.
Fractional distillation of crude oil
This is a Physical Process that includes the splitting of Van der Waals forces
Petroleum is a mixture mainly of alkane hydrocarbons
The process The crude oil is pre-heated in a furnace the mixture of liquid and vapor passes into a column
The fractions condense at different heights
The temperature of the column is cooler at the top than it is at the bottom
The separation depends on boiling point