CHEM 2332H Lecture Notes - Aldehyde, Prut, Keta

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15 Jul 2014
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Rxn taking place @ end of pi system. Disrotatory: defines rotation @ ends of pi system as like (same torque sense -->conrotatory) or unlike (opposite torque -->disrotatory) #electrons = 4n + 2 dis dis con heat light (hv) focus here. Want to rotate the double bonds (have the in and out groups be up and down) so that the pi bonds overlap and then can make a sigma bond with itself. Need to rotate both bonds in the same direction (but can arbitrarily choose which direction to rotate) In above example, since 2 torques line up (rotate in same direction) --> conrotatory. The in and out groups are trans to each other (can see by trying to rotate hands with pinky and thumb as in and out groups respectively) This molecule is chiral, get its enantiomer when you flip it. Since the beginning molecule is achiral and then -->chiral, produces racemic mixture ex: 4n + 2 case.