Oh, Markovnikov. That dude has opinions. For additions to alkenes, the major product puts the positive part (like H+) on the carbon with the most hydrogens already. That gives you the most stable carbocation as an intermediate. Then the negative part (like Br-) grabs the other carbon. Easy peasy.
But if you’re dealing with peroxide or a radical reaction, it flips to anti-Markovnikov. That’s the one time you deliberately go against the rule. It’s like breaking a traffic law because a cop told you to—it’s still legal, just different.
Answered: Draw the most stable form of the major product in the
Let’s talk about that “most stable form” trap.
Sometimes the major product isn’t the kinetic product (the fast one). It’s the thermodynamic product (the one that chills forever). This is huge in reactions like Diels-Alder or conjugate additions. The kinetic product might form quickly but be unstable. The thermodynamic product takes its sweet time, but once it shows up, it dominates.
So if the problem says “under thermodynamic control,” you’re drawing the most substituted alkene or the most conjugated molecule. If it says “kinetic control,” you might draw the less stable one that formed first. Always read the fine print. Chemistry is like dating—timing matters.
