CHEM 10052 Lecture Notes - Lecture 25: Markovnikov'S Rule, Hydrohalogenation, Regioselectivity

• School: Kent State University
• Department: Chemistry
• Course: CHEM 10052
• Professor: Pritha Subramanian

Document Summary

C=c p bond is converted to two new sigma bonds. C=c double bonds often found in the structures of pheromones. Alkenes are critical precursors in the chemical industry. 70 billion pounds of propylene (propene) and 200 billion pounds of ethylene (ethene) are both made from cracking petroleum each year. The higher the temperature, the more important entropy becomes: Sigma bonds are stronger (more stable) than p bonds. Two molecules combine to form one product; entropy decreases. At lower temps, enthalpy dominates, and addition reactions are favored. At higher temps, entropy dominates, and elimination reactions are favored. So, we use lower temperatures when doing an addition reaction. Hydrohalogenation: addition of h-x to an alkene can use hcl, hbr, or hi. If the alkene is not symmetrical, then two regioisomers are possible, depending on which carbon gets the h and the x . In 1869, markovnikov observed the h atoms tend to add to the carbon already bearing more h atoms.