Although isomers have same chemical formula but they certainly don’t behave in similar manner during a chemical reaction. This is because structure of a compound is key to unlock the specific behavior of the compound. One of the reasons of different behavior of the isomeric form is functional group. It is a specific group of atoms that imparts specific behavior to the whole compound, like OH in alcohol (CH3OH).
Let’s take an example of fructose and glucose. Both have chemical formula as C6H12O6 but the chemical arrangement of atoms and functional groups are different. In glucose, the functional group is aldehyde (CHO) at the position of carbon 1, but in fructose the functional group is a ketone (C=O group ) at the position of carbon 2. Glucose also has a six ringed structure while fructose has a five ringed structure (as depicted in figure).
How they differ in behavior?
Though glucose and fructose both are sugar, but due to different chemical structures they differently behave in human body. For example, consuming diet rich in glucose can greatly increase the insulin levels and lower the activity of brain. In contrast, increased consumption of fructose can cause smaller increase in insulin level and increase the productivity of brain.
