Example: esterification of benzoic acid to methyl benzoate MECHANISM ( Fischer esterification) reaction to give a high yield; the equilibrium must be shifted toward the products: the desired ester, and water This can products ( equation)
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Methyl benzoate fischer esterification lab report Back to Table of Contents I Summary In this experiment you will prepare methyl benzoate by reacting benzoic
[PDF] Methyl benzoate - classes link 1
This Fischer esterification reaction reaches equilibrium after a few hours of In this experiment you will prepare methyl benzoate by reacting benzoic acid with In addition to the requirements listed in the syllabus for creating a lab report, your
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Reaction: Place 6 1 g of benzoic acid and 20 mL of methanol in a 100-mL round- bottomed Shake the funnel to extract methyl benzoate and benzoic acid into the MECHANISM (Fischer esterification) O materials and products (equation )
[PDF] Lab9 methyl benzoate handout1
Example: esterification of benzoic acid to methyl benzoate MECHANISM ( Fischer esterification) reaction to give a high yield; the equilibrium must be shifted toward the products: the desired ester, and water This can products ( equation)
[PDF] 5310 F17 Experiment 5: Fischer Esterification - MIT OpenCourseWare
Fischer Esterification: The Organic Synthesis, Isolation, Purification, and Concentrated sulfuric acid is used in this lab and causes severe burns on skin and chemistry results to determine the structure and identity of your unknown sample
[PDF] 5310 F17 Experiment 5: Fischer Esterification - MIT OpenCourseWare
Fischer Esterification: The Organic Synthesis, Isolation, Purification, and Concentrated sulfuric acid is used in this lab and causes severe burns on skin and chemistry results to determine the structure and identity of your unknown sample
[PDF] Esterification Lab Report - teachmeeduvn
22 sept 2008 · LAB REPORT ON A FISCHER ESTERFICATION ESSAY 848 WORDS ONE PART OF CHEMISTRY ESTERIFICATION METHYL BENZOATE
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Lab Report Components: The following must be Esters are produced by the reaction between alcohols and carboxylic acids For example, reacting Then add 2 drops of concentrated sulfuric acid to the tube a Caution: Concentrated
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1 août 2019 · Conversion of Benzoic Acid to Methyl Benzoate 10 i Reaction Scheme Results 50 Discussion 55 Chapter 5: Conclusions and Future Work derivatization for the purpose of gas chromatography is Fischer Esterification
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HandoutEsterificationandAcetalization1) Fischer Esterification: Example: esterification of benzoic acid to methyl benzoate. MECHANISM (Fischer esterification) The overall process of esterification is one involving an equilibrium among a variety of compounds, and for the reaction to give a high yield; the equilibrium must be shifted toward the products: the desired ester, and water. This can be accomplished either by removing one or more of the products from the reaction mixture as they are formed or by using a large excess of one of the starting reagents. The effect of the latter approach is obvious from consideration of the mass law relating starting materials and products (equation). Increasing the amount of either the alcohol or the carboxylic acid will result in an increase in the amount of products formed since the equilibrium constant. K, for the reaction-must remain constant at a given temperature, no matter what quantity of either reagent is used. Removing water is also a strategy and drying agents can be used, or azeotropic distillation. However, azeotropic distillation is not possible for all alcohols. O
R OH O R OH H H O R O H O R O H H H R'OH OH ROH O HR' O ROH O R' H H R OH OR' O R OR' + HCarboxylic
Acid EsterEquilibrium displaced by either
1) water removal
2) ester distillation
3) excess alcohol
O OH conc. H 2 SO 4 O OMe + xs MeOH + H 2 O benzoic acid methyl benzoateProblem Assignment THIS PROBLEM MUST BE ANSWERED IN YOUR NOTEBOOK AND WILL BE PART OF YOUR GRADE Assuming the equilibrium constant for the esterification of benzoic with methanol is K = 3, calculate the theoretical yield of methyl benzoate expected using the following conditions: of benzoic acid and 20 mL of methanol, and 2 mL of concentrated sulfuric acid. Concentrated sulfuric acid is a dded as a catalyst in the esterific ation procedure, e ven though another a cid (benzoic acid) is one of the organic reagents used. Why is the sulfuric acid necessary? Azeotropes can be distilled using a Dean-Stark trap. If the azeotrope separates into two phases upon cooling, then water can be removed. This is the case with water/toluene and water/benzene (among other). For example benzoic acid + n-BuOH can be esterified (with H2SO4) as a catalyst, without using a large excess of alcohol. Think about how the Dean-Stark trap (glassware below) might work. ROH
O + R'OH R OR' O + H 2 O K K = [RCOOR'] [H 2 O] [RCOOH] [R'OH]To remove water as it is forming, a drying agent can be used, or a Dean-Stark apparatus if the solvent forms an azeotrope Distilling receiver - Dean-Stark apparatus Distillation of azeotropes
EQUILIBRIA, RATES, ENERGY DIAGRAMS, MECHANISMS LeChatelier'sPrinciple:asystematequilibriumrespondstoadisturbance/stresssoastominimizethedisturbance/stress.2)Acetalization(acetalformation)JLM/05 EQUILIBRIA, RATES, ENERGY DIAGRAMS, MECHANISMS TABLE: Relationship between Keq and !Go !Go (kcal/mol) Keq More stable state (%) 0 1 50 0.1 1.2 54.5 0.24 1.5 60 0.5 2.4 69.7 0.82 4.0 80 1 5.4 84.4 1.30 9 90 2 29.3 96.7 2.72 99 99 5 4631 99.98 10 2.1 x 107 99.999996 K = 10
-!G o /2.3RT !G o = -2.3RT logK!G o = -RT lnK K = e -!G o /RT Note: at 25oC, the value of 2.3RT is about 1.4 kcal/mol 50 6070
80
90
100
0123456
Relationship Between Energy Difference and Distribution % of more stable stateFree energy difference (kcal/mol)
Le Chatelier's Principle: a system at equilibrium responds to a disturbance/stress so as to minimize the disturbance/stress. TABLE: Approximate A Values (Free Ene rgy Difference between Equatorial & Axial Substituents on a Cyclohexane Ring Functional Group Approx. !Go kcal/mol Functional Group Approx. !Go kcal/mol Functional Group Approx. !Go kcal/mol HgCl - 0.25 OMe 0.6 CH=CH2 1.7 HgBr 0.0 OH (protic sol) 0.9-1.0 CH3 1.8 CN 0.15-0.25 OH (aprotic sol) 0.5-0.6 C2H5 1.8 F 0.25 NO2 1.1 i-Pr 2.1 I 0.46 SPh 1.1-1.2 C6H11 2.2 Br 0.5-0.6 COOEt 1.1-1.2 Me3Si 2.5 OTs 0.51 COOMe 1.3 Ph 2.8 Cl 0.52 COOH 1.4 t-Bu 4.9 OAc 0.71 NH2 1.4 O
R 2 R 1 OH R 2 R 1 OHO R 2 R 1 HO OR hemiacetal R 2 R 1 O OR H H R 2 R 1 O O R H H RACETAL FORMATION
H R O R 2 R 1 2 ROH cat. H R 2 R 1 ROOR H O R 2 R 1 H O R 2 R 1 H H pKa -5 to -10 H O R 2 R 1 R R 2 R 1 OO H R OH R R H R 2 R 1 ROOR acetal This reaction is reversible, so acetal hydrolysis has the same mechanism going in the backward direction. The equilibria are controlled by either removal of water or by using an excess of reagents (water or alcohol)ACETAL HYDROLYSIS
O R 2 R 1 cat. H R 2 R 1 ROORH 2 O Hemiacetal:Related reaction: alcohol protection to ROTHP (THP = tetrahydropyranyl) O DHP (dihydropyran) H O H O H because of this resonance stabilization the isomer does not form OH less stable OH R OO R OO R H H ROTHPRelated reaction: enol ether hydrolysis
RO H O H RO H R H 2 O O OR H H H same intermediates as above O H O H HO OH H H OH OH H H OH O H HO OH H H H OH H OH OH !-pyranose "-pyranoseHEMIACETALS
carbohydrates: [C(H 2 O)] n O H HO OH H H OH H OR OH (disaccharide, polysaccharide)R = sugar
ACETALS
TheAnomericEffectConformationalanalysisofcyclohexanesOriginoftheanomericeffect:thelonepairontheringoxygen(HOMO)interactswiththeC-Xantibondingorbital(σ*), thus stabilizing the axial conformer. JLM/05