Reactant Prioritization?

📌 CONCEPT: In organic chemistry, reactant prioritization is the process of determining which reactant will be more reactive or readily available for a chemical reaction to occur.

📐 RULE / FORMULA: According to the principle of reactivity, the reactant with the higher degree of unsaturation or the one with the more electron-rich atom will be prioritized for chlorination.

💡 WORKED EXAMPLE: In the given reaction, 2-methylpropane and propane react with Cl2. Propane will be chlorinated first because it has a higher degree of unsaturation (i.e., a double bond is not present, but it has a more electron-rich carbon atom). This is due to the presence of a single bond between the two carbon atoms in propane, making it more reactive towards chlorine.

⚠️ COMMON MISTAKE: Students often mistake the degree of unsaturation with the presence of a double bond. However, the degree of unsaturation also includes the presence of rings and lone pairs of electrons, which can also contribute to the reactivity of a reactant.