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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: docteurdeno on February 10, 2021, 12:18:11 PM

Title: Enthalpy of combustion and formation trends of different functional groups
Post by: docteurdeno on February 10, 2021, 12:18:11 PM

I'm planning to investigate the factors that affect the combustion and formation enthalpies on different organic compounds as a part of my chemistry project. I have two independent variables: the carbon chain length of a compound, and the functional group. I have compiled the combustion and formation enthalpies of 15 different compounds as shown here: https://imgur.com/a/slmuBco

I have then plotted these data on graphs. (Carbon chain length/enthalpy)
Combustion: https://imgur.com/a/huoI3eh
Formation: https://imgur.com/a/e3ZDnzW

I don't quite understand why the combustion enthalpy follows a trend where carboxyl>carbonyl>hydroxyl but the formation enthalpy follows a trend where carbonyl>hydroxyl>carboxyl. Also, 1-propanol seems to deviate from the general trend, and I don't know why. If you can help me out, I would really appreciate it.

Title: Re: Enthalpy of combustion and formation trends of different functional groups
Post by: mjc123 on February 11, 2021, 06:45:27 AM

The apparent anomaly of 1-propanol would seem to be due to a misreading in plotting your graph. All the series in your table are monotonic.