Alkanes and alkenes combustion reactions (organic compounds – chemistry)

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2 responses to “Alkanes and alkenes combustion reactions (organic compounds – chemistry)”

1. 

   afiq

   2024-02-10

   hello, i wonder if we compared the combustion of alkane and alkene, which one will will undergo combustion longer. Next, which fire will have more intensity and why alkene produce more soot compare to alkane

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   1. 

      Kayla Moorcroft

      2024-02-13

      Hi. So the main difference between the two is that alkenes have a double bond and alkanes don’t. This double bond makes alkenes more reactive since it is unsaturated (you can add more H’s by breaking the C=C bond). Because of this, it will combust quicker – so if you have the same amount of a specific alkene or alkane (eg. propane vs propene), the alkene will burn up that amount quicker.

      Also, because alkenes are so reactive, it needs a lot of oxygen. However, if there isn’t enough, incomplete combustion will take place and form carbon monoxide (or even carbon!). Carbon is where the soot comes from. Since incomplete combustion will happen quicker with alkenes, it produces more soot than the corresponding alkane.

      I’m not sure what you mean with “intensity of fire” so I’ll assume you mean temperature / energy. In general, since the combustion of alkenes is a faster reaction, it will release energy quicker than the alkanes reaction (even though the enthalpy for combustion of alkanes is higher). So this means the fire of alkene burning is probably warmer. Note that this isn’t the full picture because flames are complex. I’m just trying to answer a related question.

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