Show the reaction between the aldehyde and the ylide and show the mechanism of the reaction.

Answer 1

The reaction between an aldehyde and a ylide is known as the Wittig reaction. The reaction converts the carbonyl group of the aldehyde into an alkene using a phosphorus ylide. The general reaction scheme is as follows:

RCHO + CH2PPh3 -> RCH=CH2 + Ph3PO

Here R represents an alkyl group. The ylide, which is often generated in situ from a phosphonium salt, reacts with the carbonyl group of the aldehyde to form a betaine intermediate. This intermediate then undergoes a 1,2-elimination reaction to give the alkene product and the phosphine oxide byproduct.

The mechanism of the Wittig reaction involves the formation of a four-membered ring intermediate, known as a betaine. The oxygen of the carbonyl group attacks the phosphorus atom of the ylide, leading to the formation of the betaine intermediate. This intermediate undergoes a proton transfer and a 1,2-elimination reaction to yield the alkene product and the phosphine oxide.

Overall, the Wittig reaction is a powerful method for the synthesis of alkenes from aldehydes and is widely used in organic chemistry.