Dr. Ping Luo Department of PE and Health CSU Stanislaus Fall, 2004
Anleel J. Shabdin, Michael D. Drake* - CSU Stanislaus
1
Fischer Esterification and Perturbing the Equilibrium • Given that it is safe, cheap, and versatile, we will use Fischer Esterification to synthesize the esters. Ester Synthesis Strategies There are many methods by which esters can be successfully synthesized. 1) Diazomethane 2) Acid Chlorides 3) Fischer Esterification pros: high yields cons: limited to methyl esters diazomethane is explosive pros: high yields, more versatile cons: extra synthetic step HCl and SO 2 byproducts pros: safe, cheap, and versatile cons: equilibrium can give low yields Emil Fischer http://www.nobelprize.org/nobel_prizes/ chemistry/laureates/1902/fischer-bio.html • However, the matter of low yields must be addressed. • Le Châtelier’s principle can be invoked, stressing the equilibrium thereby boosting yields. 1) use an excess of one reagent over the other 2) remove one product as it forms 3) do both 1 and 2 – our choice! Fischer Esterification Reaction Mechanism 1. The carboxylic acid and alcohol (7.0 mL if liquid, 7.0 g if solid), along with 0.1 mL 18 M H 2 SO 4 were combined in a round bottom flask. 2. A Dean-Stark trap and a water- jacketed condenser were affixed to the flask. 3. The reaction was refluxed for 1.5 hours. Henri-Louis Le Châtelier http://en.wikipedia.org/wiki/File:Lechatelier.jpg A Dean-Stark trap will remove water as it forms. General Procedure for the Synthesis of All Esters 4. The ester product was isolated by acid/base extraction and purified by distillation. 5. 1 H NMR and 13 C NMR spectra were acquired. full apparatus (insulated) Dean-Stark (unwrapped) therm. position close-up vacuum distillation Results: NMR Spectra of a Selected Ester nonet expansion and expansion 1 H NMR Spectrum of Isobutyl Propanoate 13 C NMR Spectrum of Isobutyl Propanoate Synthesis of Fragrant Esters: Development of a New Organic Chemistry II Laboratory Experiment Anleel J. Shabdin, Michael D. Drake* Department of Chemistry California State University Stanislaus, Turlock, CA Esters are a class of simple organic molecules, some of which mimic natural flavors and aromas. valencene patchoulol Extracted from the vanilla bean. Natural Flavors Molecule Source Extracted from the peel of the Valencia orange. Derived from Pogostemon cablin, an herb of the mint family. Used in perfumery and incense. Image courtesy of http://kleinridge.com Image courtesy of http://4.bp.blogspot.com Image courtesy of http://marionkay.com vanillin Image courtesy of http://www.musingsofamuse.com Image courtesy of http://www.ryderfleetproducts.com Artificial Flavors Molecule ethyl cinnamate (cinnamon) bornyl acetate (pine) octyl acetate (orange) Image courtesy of http://www.thedallassocials.com Abstract The goal of this project was to develop an Organic Chemistry II (CHEM 3022) laboratory experiment for the synthesis of a variety of fragrant esters. The students will be given an unlabeled carboxylic acid, with a paired alcohol, and are expected to synthesize the ester by way of a uniform Fischer esterification procedure. They must then identify the resulting ester, as well as their unknown starting materials. The common procedure for the synthesis of 14 esters was developed. A Dean-Stark trap was used to stress the esterification equilibrium, which resulted in production of esters with percent yields that ranged from 79% to 17%. The esters were purified by distillation and characterized by 1 H NMR and 13 C NMR. Introduction Although the aroma of fruits and flowers often results from a combination of fragrant molecules, some natural fragrances or flavors can be attributed to a single compound. Results: Percent Yields After Purification Future Work • Write a laboratory procedure to be used by Organic Chemistry II (CHEM 3022) students at CSU Stanislaus. Acknowledgments • CSU Stanislaus Research Scholarly & Creative Activities 2011-2012 Grant 17% 56% 54% 59% 56% 56% 55% 61% 61% 62% 79% 67% 49% 46%
Transcript of Anleel J. Shabdin, Michael D. Drake* - CSU Stanislaus
Fischer Esterification and Perturbing the Equilibrium
• Given that it is safe, cheap, and versatile, we will use Fischer Esterification to synthesize the esters.
Ester Synthesis Strategies There are many methods by which esters can be successfully synthesized. 1) Diazomethane 2) Acid Chlorides 3) Fischer Esterification
pros: high yields cons: limited to methyl esters diazomethane is explosive
pros: high yields, more versatile cons: extra synthetic step HCl and SO2 byproducts
pros: safe, cheap, and versatile cons: equilibrium can give low yields
Emil Fischer http://www.nobelprize.org/nobel_prizes/
chemistry/laureates/1902/fischer-bio.html
• However, the matter of low yields must be addressed. • Le Châtelier’s principle can be invoked, stressing the equilibrium thereby boosting yields. 1) use an excess of one reagent over the other 2) remove one product as it forms 3) do both 1 and 2 – our choice!
Fischer Esterification Reaction Mechanism
1. The carboxylic acid and alcohol (7.0 mL if liquid, 7.0 g if solid), along with 0.1 mL 18 M H2SO4 were combined in a round bottom flask. 2. A Dean-Stark trap and a water- jacketed condenser were affixed to the flask. 3. The reaction was refluxed for 1.5 hours.
Henri-Louis Le Châtelier http://en.wikipedia.org/wiki/File:Lechatelier.jpg
A Dean-Stark trap will remove water
as it forms.
General Procedure for the Synthesis of All Esters
4. The ester product was isolated by acid/base extraction and purified by distillation. 5. 1H NMR and 13C NMR spectra were acquired.
full apparatus (insulated)
Dean-Stark (unwrapped)
therm. position close-up
vacuum distillation
Results: NMR Spectra of a Selected Ester
nonet expansion
and
expansion
1H NMR Spectrum of Isobutyl Propanoate 13C NMR Spectrum of Isobutyl Propanoate
Synthesis of Fragrant Esters:
Development of a New Organic Chemistry II Laboratory Experiment Anleel J. Shabdin, Michael D. Drake*
Department of Chemistry California State University Stanislaus, Turlock, CA
Esters are a class of simple organic molecules, some of which mimic natural flavors and aromas.
valencene
patchoulol
Extracted from the vanilla bean.
Natural Flavors Molecule Source
Extracted from the peel of the Valencia orange.
Derived from Pogostemon cablin, an herb of the mint
family. Used in perfumery and
incense.
Image courtesy of http://kleinridge.com
Image courtesy of http://4.bp.blogspot.com
Image courtesy of http://marionkay.com vanillin
Image courtesy of http://www.musingsofamuse.com
Image courtesy of http://www.ryderfleetproducts.com
Artificial Flavors Molecule
ethyl cinnamate (cinnamon)
bornyl acetate (pine)
octyl acetate (orange)
Image courtesy of http://www.thedallassocials.com
Abstract The goal of this project was to develop an Organic Chemistry II (CHEM 3022) laboratory experiment for the synthesis of a variety of fragrant esters. The students will be given an unlabeled carboxylic acid, with a paired alcohol, and are expected to synthesize the ester by way of a uniform Fischer esterification procedure. They must then identify the resulting ester, as well as their unknown starting materials. The common procedure for the synthesis of 14 esters was developed. A Dean-Stark trap was used to stress the esterification equilibrium, which resulted in production of esters with percent yields that ranged from 79% to 17%. The esters were purified by distillation and characterized by 1H NMR and 13C NMR.
Introduction Although the aroma of fruits and flowers often results from a combination of fragrant molecules, some natural fragrances or flavors can be attributed to a single compound.
Results: Percent Yields After Purification
Future Work • Write a laboratory procedure to be used by Organic Chemistry II (CHEM 3022) students at CSU Stanislaus.
Acknowledgments • CSU Stanislaus Research Scholarly & Creative Activities 2011-2012 Grant
17%
56% 54%
59%
56% 56% 55%
61% 61%
62%79% 67%
49% 46%
