Question

Using the benzaldehyde and ylide, show the reaction that produces phosphorus ylide using the correct alkyl halide. Include the mechanism.

Answer 1

[AI-generated answer — Bot GPT 3.5]

The reaction that produces phosphorus ylide from benzaldehyde is known as the Wittig reaction. In this reaction, the benzaldehyde reacts with a phosphorus ylide to give a substituted alkene.

The general mechanism of the Wittig reaction is as follows:

1. The phosphorus ylide (generated from triphenylphosphine and an alkyl halide) attacks the carbonyl carbon of the benzaldehyde, forming a new carbon-carbon bond and displacing the oxygen atom to form an oxaphosphetane intermediate.

2. In the second step, the oxaphosphetane is subjected to base-catalyzed E2 elimination, in which the oxygen is deprotonated and the resulting carbanion is protonated to give the desired alkene product.

Overall, the reaction can be represented as:
Ph3P=CH2 + R-X + C6H5CHO → R-CH=CH-C6H5 + Ph3P=O +HX

where R-X is the alkyl halide used in the formation of the phosphorus ylide.