Hydrocarbon Reactions

Previous: Halogens

Hydrocarbons are prone to various kinds of reactions.

We have already seen oxidation in burning: C17H36 + 26O2 → 17CO2 + 18H2O.

As a revision exercise, you might like to determine the mass of heptadecane that will need to be burnt to produce 162g of water? (Is it 120g?)

Another group of reactions converts hydrocarbons into their 'derivatives'. These are molecular-covalent compounds with functional groups, usually involving oxygen, nitrogen or a halogen such as chlorine. Sometimes two or all three of these are involved, and occasionally other elements as well.

One such reaction is called substitution. In a substitution reaction one kind of atom, say bromine, is substituted for another, inevitably hydrogen.

or →

Itís simple. Itís cheap. Itís unpredictable. Given these reactants, itís very difficult to produce only 2,3-dibromopentane. Some 1,2-dibromopentane would also result, and some means of separating them would be required.

Or consider this reaction:


One functional group is substituted for another. Not so simple, but more predictable.

Another such reaction is called addition. Addition reactions require an unsaturated hydrocarbon. This means it at least one double or triple carbon-carbon bond is present; there must be an -ene or an -yne.


Bromine is added to the hydrocarbon, nothing is removed.

 

These are the only functional group reactions covered in Physical Science. If you want more, do Chemistry next year.

Next Page: Polymers

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