Energy changes and bonding
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I would like to investigate the relationship between alcohol classification (primary, secondary or tertiary) and combustion - looking at the energy of combustion (used to raise the temp of a known mass of water) and the amount of alcohol reacted with the oxygen (difference in masses before and after).
I was just wondering how to go about this and also if there was any research about this relationship because I haven't been able to find any. Thanks.
Igloo writes ...
From the first paragraph of your question it appears that you know what to do from a practical point of view, so I shall assume that your question is concerned more with the theory.
Carry out three combustion experiments with primary, secondary and tertiary alcohols having the same molecular formula, e.g. butan-1-ol, butan-2-ol and 2-methylpropan-2-ol and determine the enthalpies of combustion in each case.
You should find that the primary alcohol gives out the greatest energy per mole and the tertiary alcohol gives the least. This implies that the tertiary alcohol is a little less stable than its primary counterpart, i.e. the internal molecular bonding is a little weaker. However, the difference is only small (about 1%) and it is certain that your experimental errors would mask this difference.
Therefore I do not think that your experiments are going to give you any fruitful data, so I recommend that you shelve your ideas and think of something else. I am sorry to sound discouraging, but it’s better to know now than to find out when it’s too late to think of something else!
Always carry out a risk assessment and check with your teacher before starting any practical work.
Risk assessment
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updated: 27 October 2007
