CHz + PhP-CHCH3 – CH3 НАС НАС Aldehydes and ketones are converted into alkenes by means of a direct nucleophilic addition called the Wittig reaction phosphorane, adds to an aldehyde/ketone to give a four-membered cyclic intermediate called an oxaphosphetane. The decomposes to release triphenylphosphine oxide and an alkene. The ylide is formed by reaction of triphenylphosphine, a good nucleophile, with a primary alkyl halide in an Sy2 react base, such as butyllithium. The carbonyl carbon and the carbon originally bonded to the halogen become the two carbon The real value of the Wittig reaction lies in its ability to yield an alkene of predictable structure, as the C-C bond is pres isomers (other than E/Z isomers) are formed. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions :0-PPh3 H₃ C CH₃ cô=PPha H₃C CH3 Нас- н Et H