By: Krishnaa Siva
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
Benzaldeh yde Ylid
Fall 2012
2
Melting Point ( C) ̊
106.12 348.3767
-26 124-129
178.1 -
-96 - -94
68-69
0.6548
6.5-8
271
1.046
Hexanes Ethyl cinnamate
86.18
176.21
Boiling Point ( C) ̊
Densit y (g·cm− 3)
Molar mass (g/mol)
1.0415 -
Volume/ Mass ~0.11 mL (0.106g) 0.348 g 5-10 mL Theoretical: 0.173 g Experiment al: 0.15 g
Moles 0.001 0.001 0.038 moles 0.076 moles Theoretical: 0.001 Experimental: 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 liquid b. Figures: IR and NMR Spectra i. IR Spectrum of crude wittig product– attach and label important stretching frequencies ii. NMR Spectra of crude wittig product – attach and list data for all 1H’s (chemical shift, multiplicity, coupling constant, identity) Appearance
6. Discussion: 4 marks a. Discussion of Yield – crude, purified, % recovery – why less than 100%?
Chemistry 222
Fall 2012
3
This experiment resulted in have a 87% yield of ethyl cinnamate with the experiment yield of ethyl cinnamate being 0.15 g, while the theoretical yield being 0.173 g. This shows that there were very few errors human and experimental errors made in this experiment. When adding the benzaldehyde to the flask containing the ylid, there is a good chance that only the bottom part of the benzaldehyed reacted with the ylid. Some of the top portion of the benzaldehyde that was added with the syringe failed to react with the ylid and this results in a loss of product. The transfer into something else (flask) could have resulted in a loss of product as well. All in all, there is very little chance for error in this experiment. b. Discussion of Spectral Data – evidence for correct product i. Analysis of IR spectra (crude/pure), NMR spectra (crude/pure) The IR spectrum did provide some useful information that help verify the correct product was formed. In the IR spectrum, the C=0 stretch found near the 1703 cm-1 is indicative of the carbonyl found in ethyl cinnamate. There is also the C=C alkene stretch that can be seen at 1636 cm-1 Moreover, the C-O stretch found at 1163.66 cm-1 is indicative of the C-O stretch found in ethyl cinnamate. A benzaldehyde does not have this C-O stretch. This supports the idea that the product was indeed formed. In the NMR Spectrum, there is an aromatic stretch found near the 7.1-8 ppm region and this corresponds to all the hydrogens found in the aromatic ring of the ethyl cinnamate. There is also quartet found near the 4.26 ppm region, and this corresponds to the hydrogens attached to the carbon which has another carbon attached to it containing three hydrogens. There is also a triplet stretch near the 1.3 ppm region and this is indicative of the hydrogens attached to a carbon with another carbon attached to it containing 2 hydrogens. These last two stretches correspond to the ethyl found in ethyl cinnamate. There is also a doublet stretch (vinylic) near the 6.5 ppm region and this is indicative of the alkene part of the product. The other doublet due the alkene is near the aromatic stretches (at ~7.9 ppm). These doublets are as a result of having a proton attached to a carbon that is attached to another carbon with one hydrogen. One part of the alkene is in the aromatic region since it is closer to the aromatic group, while the other part is closer to the carbonyl group. All in all, all these characteristics give evidence that the correct product was formed. c.
Mechanism – detailed mechanism for the wittig reaction of your reactants
Chemistry 222
Fall 2012
4
References Hunt, Ian. "Chapter 17: Aldehydes and Ketones. Nucleophlic Addition to C=O: The Wittig Reactiong". University of Calgary Faculty of Science. Oct 2011. Web. 25 Nov. 2012. Solomons, T.W.G. Graham, Fryhle, Craig and Johnson, Robert. Organic Chemistry. 10th ed. New York: John Wiley & Sons, 2009. Print.
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
Benzaldeh yde Ylid
Fall 2012
2
Melting Point ( C) ̊
106.12 348.3767
-26 124-129
178.1 -
-96 - -94
68-69
0.6548
6.5-8
271
1.046
Hexanes Ethyl cinnamate
86.18
176.21
Boiling Point ( C) ̊
Densit y (g·cm− 3)
Molar mass (g/mol)
1.0415 -
Volume/ Mass ~0.11 mL (0.106g) 0.348 g 5-10 mL Theoretical: 0.173 g Experiment al: 0.15 g
Moles 0.001 0.001 0.038 moles 0.076 moles Theoretical: 0.001 Experimental: 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 liquid b. Figures: IR and NMR Spectra i. IR Spectrum of crude wittig product– attach and label important stretching frequencies ii. NMR Spectra of crude wittig product – attach and list data for all 1H’s (chemical shift, multiplicity, coupling constant, identity) Appearance
6. Discussion: 4 marks a. Discussion of Yield – crude, purified, % recovery – why less than 100%?
Chemistry 222
Fall 2012
3
This experiment resulted in have a 87% yield of ethyl cinnamate with the experiment yield of ethyl cinnamate being 0.15 g, while the theoretical yield being 0.173 g. This shows that there were very few errors human and experimental errors made in this experiment. When adding the benzaldehyde to the flask containing the ylid, there is a good chance that only the bottom part of the benzaldehyed reacted with the ylid. Some of the top portion of the benzaldehyde that was added with the syringe failed to react with the ylid and this results in a loss of product. The transfer into something else (flask) could have resulted in a loss of product as well. All in all, there is very little chance for error in this experiment. b. Discussion of Spectral Data – evidence for correct product i. Analysis of IR spectra (crude/pure), NMR spectra (crude/pure) The IR spectrum did provide some useful information that help verify the correct product was formed. In the IR spectrum, the C=0 stretch found near the 1703 cm-1 is indicative of the carbonyl found in ethyl cinnamate. There is also the C=C alkene stretch that can be seen at 1636 cm-1 Moreover, the C-O stretch found at 1163.66 cm-1 is indicative of the C-O stretch found in ethyl cinnamate. A benzaldehyde does not have this C-O stretch. This supports the idea that the product was indeed formed. In the NMR Spectrum, there is an aromatic stretch found near the 7.1-8 ppm region and this corresponds to all the hydrogens found in the aromatic ring of the ethyl cinnamate. There is also quartet found near the 4.26 ppm region, and this corresponds to the hydrogens attached to the carbon which has another carbon attached to it containing three hydrogens. There is also a triplet stretch near the 1.3 ppm region and this is indicative of the hydrogens attached to a carbon with another carbon attached to it containing 2 hydrogens. These last two stretches correspond to the ethyl found in ethyl cinnamate. There is also a doublet stretch (vinylic) near the 6.5 ppm region and this is indicative of the alkene part of the product. The other doublet due the alkene is near the aromatic stretches (at ~7.9 ppm). These doublets are as a result of having a proton attached to a carbon that is attached to another carbon with one hydrogen. One part of the alkene is in the aromatic region since it is closer to the aromatic group, while the other part is closer to the carbonyl group. All in all, all these characteristics give evidence that the correct product was formed. c.
Mechanism – detailed mechanism for the wittig reaction of your reactants
Chemistry 222
Fall 2012
4
References Hunt, Ian. "Chapter 17: Aldehydes and Ketones. Nucleophlic Addition to C=O: The Wittig Reactiong". University of Calgary Faculty of Science. Oct 2011. Web. 25 Nov. 2012. Solomons, T.W.G. Graham, Fryhle, Craig and Johnson, Robert. Organic Chemistry. 10th ed. New York: John Wiley & Sons, 2009. Print.
