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Pictures of the Day

1-25-2024

Above is shown the simplest Wittig reagent, namely the ylide made from a methyl halide and triphenyl phosphine. Note how in the electrostatic potential surface the negative charge is on the carbon atom, explaining why it is such a good nucleophile and reacts with carbonyl groups
Shown here is the four-membered ring intermediate that occurs when the Wittig reagent derived from a methyl halide reacts with acetone. The unique feature of the Wittig reaction is the mechanism in whichthe famous four-membered ring intermediate, called an oxaphophetane, is formed. This is completely different than the other reactions we have seen,(it does not follow Mechanisms A-D). When you think Wittig, I want you to think four-membered ring intermediate.