# How does the relative amount of oxidation of different alcohols affect the amount of energy released?

I am investigating the enthalpy of combustion of different primary alcohols and a website I found briefly mentioned how the relative amount of oxidation of different alcohols affects the amount of energy released. I was wondering if anyone could possibly elaborate on this.

I also found a trend where carbon chain length 1 --> carbon chain length 2 has a great increase in experimental heat of combustion but then there is a smaller increases between carbon chain length 2 and 3. Would there be an explanation for this (I have a feeling it relates to incomplete combustion)?

Thanks!

This effect is most pronounced for the low-molecular weight alcohols. Methanol has 1 oxygen per carbon atom, while ethanol has 0.5 oxygens per carbon atom. That is a much larger relative difference than there is between a $\ce{C10}$ alcohol and a $\ce{C11}$ alcohol. In other words, the larger a mono-hydroxy alcohol is, the more it resembles a pure alkane with respect to the enthalpy of combustion.