Molecules that have only single bonds and contain the maximum amount of hydrogen are saturated hydrocarbons. Each ring, or each extra bond added on a single bond making it a double or triple bond , in an unsaturated hydrocarbon will reduce the number of hydrogen atoms in the molecule by 2, which is referred to as adding one degree of unsaturation. The general chemical equation for combustion of a hydrocarbon is:. Compared to the combustion of saturated hydrocarbons , unsaturated hydrocarbons will release less water per molecule of hydrocarbon combusted, and also consume less oxygen.
For every mol of ethene combusted, 0. There are fewer high- energy bonds in unsaturated hydrocarbons compared to saturated hydrocarbons of the same size , unsaturated hydrocarbons will release less energy per molecule when combusted. The same meaning of unsaturated used here for hydrocarbons is also used to describe fats and oils, which are hydrocarbon derivatives. Alkanes do this slowly. Alkenes can be used as fuels, solvents and starting materials for everyday products such as plastics and alcohol.
Naming alkenes has the same rules as alkanes. However, the position of the carbon to carbon double bond must be identified. Note that the functional group in the case of alkenes, the double bond is given the lowest possible number first, before any branches are numbered.
The formula will be C 10 H Hexene is an alkene. Its molecules contain 6 carbon atoms. Predict the molecular formula of hexene. The formula will be C 6 H The table shows four alkenes, their molecular formulae and their structures.
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