I have a clear liquid with a faint sweet smell. I know this compound contains an aromatic group and an ester. However, something strange happens when I try to distill it - it forms a white solid. I believe this solid to be the result of thermal decomposition of the ester - the ester reacting with oxygen in the air. I have searched around, but can't find much written about thermal decompositions of esters. What reaction is this? What is the product? Could it be a carboxylic acid?
Well, you are right. Esters decomposes at higher temperatures to form several small carboxylic acids and ketones and at even higher temperature, these carboxylic acids decomposes into carbon monoxide, carbon dioxide, carbon, oxygen and/or water. A paper discusses about the thermal decomposition of ethyl formate, ethyl acetate and ethyl propanate at 1248-1638 K, pressure around 1.5 atm at a chamber filled with argon at a concentration of 2000 ppm.
After the experiment, it was found out that 90% of oxygen has been released as oxygen gas and the pyrolysis mechanism was determined to be a six-centered decomposition producing equimolar ethylene and corresponding acid and at drastic conditions, it was known to have a dehydration reaction releasing water and a decarboxylation reaction to form carbon dioxide.
It was found out that EF gave formic acid, EA gave acetic acid and EP gave methyl ketene as the main products which subsequently decomposed into various smaller products at higher temperatures and the concentration ratios were noted.