Substituents on Aromatic Aldehydes and How They Affect E/Z Selectivity in the Wittig Reaction

Abstract:The Wittig Reaction is a nucleophilic addition in which an olefin is organize as a product. Both the E and Z isomers of the alkene result. Substituents on the aromatic aldehyde affect the E/Z balance of products that form. In this experiment, a nitro base was use as the substituent in the ortho, meta and para positions, with benzaldehyde as the control. Each of the four aldehydes reacted with (carbethoxym ethyl radicalene) triphenylphosphorane to produce ethyl cinnamate, ethyl-3-(2-nitrophenyl)acrylate, ethyl-3-(3-nitrophenyl)acrylate, and ethyl-3-(4-nitrophenyl)acrylate. The prediction was the closer the substituent was to the aldehyde, the greater the dimension of E/Z isomers; benzaldehyde was predicted to result in the most correspondent dimension of E/Z isomers. The ratios of E/Z isomers were ascertain by utilise the NMR spectra obtained. A percent renascence was also obtained. Ethyl-3-(2-nitrophenyl)acrylate had a ratio of 9.03:1, ethyl-3-(3-nitrophenyl)ac rylate had a ratio of 5.2:1, ethyl-3-(4-nitrophenyl)acrylate had a ratio of 1:1 and ethyl cinnamate had a ratio of 9.3:1. The results for the compounds except ethyl cinnamate supported the hypothesis that the ratio would be closer to 1:1 as the substituent moved make headway from the carbonyl. Introduction:The manipulation of this experiment is to determine how a nitro group on benzaldehyde affects the stereoisomer system of the alkene formed in a Wittig Reaction. The nitro group is substituted in the ortho, meta, and para positions, and benzaldehyde serves as a control. The ylide used is (carbethoxymethylene) triphenylphosphorane. Through the physical exertion of NMR spectroscopy, the products of the reactions will be analyzed to gain a ratio of E /Z isomers. Reaction Equations:Ethyl cinnamate from BenzaldehydeEthyl-3-(2-nirophenyl)acrylate from O-nitrobenzaldehydeEthyl-3-(3-nitrophenyl)acrylate from M-nitrobenzaldehydeEthyl-3-(4-nitrophenyl)acrylate from P-nitrobenzaldeh ydeIn 1954, Georg Wittig, a German chemist, ! discovered the Wittig Reaction. In 1979, Wittig won a Nobel regard in Chemistry repayable to the Wittig Reaction?s synthetic potential to form a variety of different alkenes. Today, this... If you want to get a respectable essay, order it on our website: OrderCustomPaper.com

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