pi bonds
"Pi bonds are like pointing two fingers at the ceiling and moving them sideways until they touch. Unlike sigma bonds, pi bonds cannot rotate and maintain the bond; you can see this in our finger model, as turning your fingers out of alignment breaks the connection. Therefore, double or triple-bonded atoms cannot rotate relative to each other."
"The two pi bonds are like two vertical sticks if you allow me to call them like that here, which when adjacent to each other turn into this bean-like shape. From this, you get a rigid bond that cannot rotate "
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