It is a known fact that when organic compounds are combusted, there is a subsequent large release of energy.
Compounds which are organic constitute and range from ketones, aldehydes to alcohols. Taking one alcohol in specific, Ethanol, has a significant and wide range of uses, one of them being Motor fuel. Unlike fossil fuels, alcohols are renewable and this is an essential property of any good fuel in the long run. But, just being renewable is not a sufficient claim for alcohols being a good fuel. I chose this topic becuase I wanted to understand what characterestics constitute a good fuel and the fact that alcohols are a renewable source made me ponder over how practical its use is as a fuel. Understanding this would help me realize to what extent alcohols are a good alternative source of energy in today’s world where alternate sources of energy are needed in order to reduce fossil fuel usage. This is why I chose the first 4 alcohols, aliphatic alcohols which are being researched upon for their uses as a fuel. When a good fuel is combusted in the presence of Oxygen, the release of energy is significantly high, when an alcohol is burnt, there is a release of energy, But, is there a correlation in the energy released from one alcohol to another ? And how does this affect the relationship between alcohols from a combustion perspective ?This research paper is dedicated towards experimenting this property.
Alcohols have a functional group ( -OH ) and therefore are a homologous series. There are many groups/families of compounds whose molecules constitute of carbon atom chains, and one such family/group are the alcohols. They have a hydroxyl ( a hydrogen and oxygen combination ) and a bond with carbon being single. Due to this sort of arrangement, alcohols can be considered as hydrocarbons. To be able to remove water from the body, is an ability alcohols generally possess, because of which hydrogen gets substituted by chains of hydrocarbons. It is also known that ?CnH2n + 1OH is the general formula for alcohols.
Therefore, the aim of this investigation is quite straightforward, aim being to examine The relationship in terms of the amount of energy that is released from a fuel ( alcohol ) and how the total number of atoms of carbon correlate with this release of energy Now, if a certain fuel has a higher availability of carbon atoms, it would be directly proportional with an increase in the number of bonds to be broken and made, and this of course would result in an overall increased energy output. Also, adding to the above paragraph, it is a known fact that for every reaction that takes place, bonds split and the formation of new subsequent bonds takes place, whilst throughout this process there is a constant rearrangement of atoms, and for all of this to be able to occur, there is an essential requirement of energy, energy being required for bond splits and a witnessed release of energy after every bond is made Hypothesis and Reasoning My initial idea was that enthalpy of combustion would have more of an inclination towards being negative as the alcohol chain gets longer with more addition of carbon atoms. Why would this be the case ? Due to the fact that the overall shape of a molecule changes with the addition of carbon atoms. Also, it is observed that a spate CH3 molecule, as one descends a homologous group, gets added into the chain.
Therefore, now we know that this is why more energy is needed to split this new molecule. Obviously, a hydrocarbon chain that is relatively longer is more difficult to split than one which is not as long because in the longer one there’s more bonds to be split. And, if we look at the alcohols, it can be seen how each subsequent alcohol has one more methylene group (-CH2-) than the alcohol preceding it.
What happens when it is combusted ? It is seen that there is the formation of one more C-C bond and simultaneously, there are 2 splits of C-H bonds. Clearly, energy required for burning is relatively higher. Another perspective, would be to consider intermolecular forces ( van der waal ) in the context of every molecule. The overall mass would have an increase if there is an addition of more carbon atoms to the already existing chain. Now, within the alcohol, there would be a significant increase in its van der waals forces which of course means increased attraction forces.
From the above, therefore, we can see how for the alcohols this would result in an increased enthalpy of combustion. Now, it is fair to assume or hypothesize that enthalpy of combustion would have more of an inclination towards being negative as the alcohol chain gets longer with more addition of carbon atoms.