Boric acid reacts with methanol in the presence of sulfuric acid which acts as a catalyst, to produce an inorganic ester, trimethyl borate. These types of reactions are known as esterification reactions. The overall process can be described by the equation:



Trimethyl borate is a liquid with a low boiling point (68 - 69°C), it is highly flammable, and can be easily ignited with a Bunsen burner. An intense green flame is observed during the combustion. This green colored flame is specific for substances that contain boron atom. However, barium or copper compounds also color the flame in green, but there are small differences in the green colors. Out of this reason, we can check if sample contains boron atoms by introducing them into a flame. This is so called flame test and is used in qualitative chemical analysis to prove the presence of specific atoms. There is a lot of physical chemistry behind the process, but it is simplified in the paragraph bellow.

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