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McGill University
CHEM 204
David Harpp

Chemistry 222 Fall 2012 1 By: Krishnaa Siva Date: November 28, 2012, Thursday 1:30-5:30 PM Lab Group TA: Mathieu Bedard Experiment 5 (Part 2): Wittig reaction 1. Objective: 1 mark What is the purpose of this experiment? To perform the Wittig reaction and synthesize ethyl cinnamate from ylid and benzaldehyde in the presence of the hexane solvent. Use IR and NMR Spectroscopy to verify if it is that product that is formed. 2. Introduction: 1 mark Brief description of the concept/reaction studied – wittig reaction The Wittig reaction involves the reacting ylide with an aldehyde or ketone, which is a carbonyl group, to form an olefin/alkene. The phosphonium ylid can be made through an SN2 reaction between the triphenyl phosphine and alkyl halide. When a stabilized ylid is used only alkenes are formed, while if an un-stabilized ylid is used alkenes and triphenyl phosphine oxide is formed. The Wittig reaction is known to be a useful reaction since it produces a double in a specific position with no uncertainty (Hunt, 2011). 3. Reaction Equation: 1 mark Include proper structures and data for reactants and products [molar mass, concentration, density, volume, mass, moles, etc – including theoretical yield] Chemistry 222 Fall 2012 2 Densit Molar Boiling y mass Melting Point (g·cm− Volume/ (g/mol) Point (̊ ) (̊ ) 3) Mass Moles Benzaldeh ~0.11 mL 0.001 yde 106.12 -26 178.1 1.0415 (0.106g) Ylid 348.3767 124-129 - - 0.348 g 0.001 0.038 moles - Hexanes 86.18 -96 - -94 68-69 0.6548 5-10 mL 0.076 moles Theoretical: Theoretical: 0.173 g 0.001 Ethyl Experiment Experimental: cinnamate 176.21 6.5-8 271 1.046 al: 0.15 g 0.0009 4. Procedure: 1 mark Summary of lab procedure – what YOU did, third person, past tense – be concise! 1.0 mmol (~0.11 mL) of benzaldehyde was mixed with 1.0 mmol (~0.35g) of ylid in a 25 ml round bottom flask for couple of minutes (was supposed to be for 15 minutes). Next, 5-10 mL of hexanes was added to the flask. The suspension was then filtered using vacuum filtration and the the flask with the contents was taken and the hexanes were evaporated. The weight of the product was obtained at the end. 5. Results: 2 marks a. Table 1: Yield and Physical Properties Crude Wittig Product Yield (g) 0.15 g Yield (%) 87 % Yellowish-transparent Appearance liquid b. Figures: IR and NMR Spectra i. IR Spectrum of crude wittig product– attach and label important stretching frequencies 1 ii. NMR Spectra of crude wittig product – attach and list data for all H’s (chemical shift, multiplicity, coupling constant, identity) 6. Discussion: 4 marks a. Discussion of Yield – crude, purified, % recovery – why less than 100%? Chemistry 222 Fall 2012
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