(Carbethoxymethylene) Triphenylphorane Lab Report

Abstract:

The main goal in our reaction was to use benzyl alcohol and (carbethoxymethylene)triphenylphosphorane along with a Wittig reagent to create ethyl cinnamate. Throughout the experiment, many observations were recorded that demonstrated the production of our product, including the production of a thick black substance. Synthesis steps were followed involving PCC and other reagents such as DCM to produce a 62.5% yield following the TLC and flash chromatography. IR and NMR were taken on the product to be able to be analyzed and discover what was made throughout the steps of synthesis. After analyzing the IR, NMR, and TLCs, it was determined that the product that was predicted was in fact present in the organic compound. It was determined

and sodium acetate (0.375g, 4.5mmol, 3 eq.). in 30 mL of dichloromethane was added benzyl alcohol (0.33g, 3 mmol, 3 eq.). and (carboxymethylene)triphenylphosphorane (0.96 g, 3 mmol, 3 eq.). This created a black liquid that had no transparency. The solution was then stirred for 1 hour and 45 minutes under reflux conditions and no color change was recorded. Once the solution was cooled, 15 mL of diethyl ether was added and the new supernatant liquid was then filtered through a pad of celite in the buchner funnel. Final liquid product is concentrated in vacuo to produce a thick, black liquid. Further purification of the black liquid was done via flash chromatography in a 95% petroleum ether/5% diethyl ether solvent system (Rf value of 0.26) to produce the final product (3a). The product was concentrated in vacuo, containing 0.3 g of ethyl cinnamate (62.5% yield) in a clear, odorless liquid (3a). Results and Discussion: In this lab, the purpose of the oxidation/Wittig “Domino” reaction was to be able to perform an oxidation reaction quickly by performing a one-pot reaction rather than adding another purification step. In the first step of the process, pyridinium chlorochromate (PCC) is the oxidizer to the benzyl alcohol. However, the PCC needs to be buffered with sodium acetate to negate PCC’s acidic properties that may affect the further reaction(5) which was done in a solution in DCM. The Wittig

Nevertheless, the IR spectrum shows that the concentration of Diethyl Ether in the final product is minimal. The reference for the product described two quartet peaks at around 4.0-4.5 (1), which were both seen in our NMR at 3.9 and 4.05 respectively, with integrations of around 2 (Appendix 6). These peaks correspond to the hydrogens in the carbon in between the methyl and the oxygen in the ethyl ester. At around 6-7.5. Two doublet peaks were expected to be present at 6-7.5. These peaks were seen at around 5.6 and 5.7 respectively, confirming the hydrogens across the alkene within ethyl cinnamate (Appendix 2). These peaks correspond to the E conformation. The reference also describes another group of downfield doublets, which are present at 6-6.1, corresponding to the Z conformation. With this, the NMR provided a product ratio of 14:1 of the E:Z conformations (Appendix 2). In the aromatic region of the NMR (7-8 ppm), there are two doublets and a doublet of triplets that correspond to the hydrogens around the phenol group (Appendix 3). Our IR Spectroscopy provides insight into both confirming our product as well as the concentration of unwanted side products in our IR