Can Alkyl Halides Be Made from Alkenes?

📌 CONCEPT: Alkyl halides can be prepared from alkenes through an electrophilic addition reaction, specifically the reaction with hydrogen halides (HX) in the presence of a catalyst.

📐 RULE / FORMULA: The Markovnikov's rule states that in the addition of HX to an alkene, the hydrogen atom adds to the carbon atom with more hydrogen atoms, and the halogen atom adds to the carbon atom with fewer hydrogen atoms, resulting in the most stable product.

💡 WORKED EXAMPLE: Consider the conversion of 2-methylpropene to 2-chloro-2-methylpropane. First, 2-methylpropene reacts with HCl in the presence of a catalyst, such as zinc chloride. The Markovnikov's rule predicts that the hydrogen atom will add to the more substituted carbon atom (C2), and the chlorine atom will add to the less substituted carbon atom (C1).

⚠️ COMMON MISTAKE: Students often forget to account for the regioselectivity of the reaction, failing to apply the Markovnikov's rule correctly, which leads to the incorrect product.