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