Morris Kharasch and Peroxides
Me: Hey, Dr. Morris Kharasch, is that you? How are you?
MK: It is me and I am great, thank you for asking. I understand you are talking about free radical chain reactions in your class. Do you want to hear my radical story?
Me. Sure, is it a happy story?
MK: No it is sad really. It turns out that in the 1940’s some chemists were trying to add HBr to alkenes and they kept getting the expected Markovnikov addition regiochemistry. Others would try to run the same reaction but would get non-Markovnikov addition regiochemistry. Both groups repeated their experiments and were positive the others were wrong. Things got ugly, name-calling at conferences, it is scary when chemists fight over mechanisms. Well, I figured it out. Peroxides build up over time in ether solvents. The chemists who saw non-Markovnikov regiochemistry unknowingly had peroxides in their ether, leading to a free-radical chain reaction mechanism with the alkene and HBr, giving the non-Markovnikov product. Now chemists do this on purpose! Using peroxide and heat, HBr adds to alkenes in a free radical process that gives non-Markovnikov regiochemistry, a very useful reaction! No peroxides and the reaction goes with Markovnikov regiochemistry.
Me: So why is this a sad story, it sounds like you are awesome!
MK: Well, I was the one who coined the term “Markovnikov” to explain the regiochemistry of the HBr reaction involving no peroxides and a carbocation intermediate. But everyone calls what I discovered the “peroxide effect”, not the Kharasch effect. Kind of sucks. Most days I am not bitter, OK some days I am not bitter. Every organic student knows the name Markovnikov because of my paper…maybe someday some will remember me…after all, I figured it all out. Peace out from here.
