Wittig reactions allow the generation of an alkene from the reaction between an aldehyde/ketone and an ylide (derived from the phosphonium salt). The mechanism for the synthesis of trans-9-(2 -phenylethenyl)anthracene first requires the formation of the phosphonium salt by the addition of triphenylphosphine and alkyl halide. Phosphonium halide is produced through nucleophilic substitution of the 1st and 2nd alkyl halides and triphenylphosphine (the nucleophile and weak base) 4 An example is the benzyltriphenylphosphonium chloride used in this experiment. The second step in the formation of the Wittig reagent which is mainly called ylide and derived from a phosphonium halide. In the formation of the ylide, the phosphonium ion in benzyltriphenylphosphonium chloride is deprotonated from the base, sodium hydroxide, to produce the ylide as shown in equation 1. The positive charge on the phosphorus atom is a strong EWG (electron group -attractor), which will activate the adjacent carbon as a weak acid 5 Very strong bases such as a lithium alkyl are needed for deprotonation, however in this experiment it was used 50% sodium hydroxide as reiterated. Finally, the reaction between the ylide and aldehyde/ketone produces an alkene.3(Eq. 1)As shown in equation 2, the reaction between the phosphonium salt and sodium hydroxide produces the ylide/carbanion which is stabilized at due to the positive charge on phosphorus and the conjugation that occurs in the benzene ring as shown by structure B in equation 2. The ylide produced also has a resonance form (B'). The resonance form is advantageous because it contains no formal charge and the double bond it contains results in the same position as the double bond in the final a...... center of the card ......e 3. Both letters A and B within the structure of trans-9-(2-phenylethenyl)anthracene, which make up the alkene, have a chemical shift between 5-6 ppm and both produce doublets because they have 1 adjacent hydrogen and according to N+1 the rule that establishes the number of hydrogens in carbon adjacent plus 1 gives the splitting pattern and the number of peaks in the splitting signal, which in this case is a doublet.1 The letters C and D which consist of the aromatic rings, both are multiplets, and have a chemical shift between 7 and 8 ppm. 1H NMR could be used to differentiate between cis and trans isomers of the product due to J coupling. When this occurs, the trans coupling will be between 11 and 19 Hz and the cis coupling will be between 5 and 14 Hz, demonstrating that cis has a slightly lower coupling constant than trans, and therefore they have their respective positions in a product. 2