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Unbranched, branched or ringed.
Almost non-polar because of similar electronegativities.
Weak V.D.W. forces.
As the chain length increases, the boiling point increases due to the number of V.D.W. forces
Alkanes with branched chains cannot pack as closely as unbranched chains, so melting points are
lower as V.D.W forces are not as effective.
Insoluble in water as the hydrogen bonds are stronger than the V.D.W.
How alkanes react:
Unreative normally. They have strong carbon-carbon/carbon-hydrogen bonds. They do burn and will
react with halogens under suitable conditions.
Fractional Distillation of Crude Oil
Crude oil is mostly a mixture of branched and unbranched alkanes.
It is done in a fractionating tower.
1. Crude oil heated in a furnace.
2. The mix of liquid and vapour passed into a tower cooler at
the top than at the bottom.
3. Vapour passes up the tower (via a series of trays containing
bubble caps) until they arrive at a tray lower than their
boiling point. They condense and are then piped off.
4. The thick residue at the bottom is tar/bitumen. It is often
processed again to provide more valuable products.
The shorter the hydrocarbon chain, the nearer the top they
condense because they have the lowest boiling points.
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Shorter chain products are more economically valuable due to supply not meeting demand.
High pressure 7000kPa
Free radicals are formed due to one electron in a paired covalent bond goes to each carbon chain in
The free radicals are highly reactive intermediates.
Alkenes are not cracked for long to avoid decomposition.
Lower temperature- 720K
Lower pressure (but more than atmospheric)
ZEOLITE CATALYST... Silicon dioxide and Aluminium oxide
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Exacerbate asthma, cause cancer.
Greenhouse gases, photochemical smog.
Produced when hydrocarbons are burned.
To remove sulfur... FLUE GAS DESULFURISATION
Some chimneys use CaO, CaCO which produces gypsum CaSO (plaster)
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