Synthesis Of Methyl Benzoate Lab Report
Exp’t 84
Synthesis of Methyl Benzoate by Fisher Esterification from K. L. Williamson, Macroscale and Microscale Organic Experiments, 2nd Ed. 1994, Houghton Mifflin, Boston p385 Revised 10/15/03
Prelab Exercise: Give the detailed mechanism for the acid-catalyzed hydrolysis of methyl benzoate. Introduction: The ester group is an important functional group that can be synthesized in a number of different ways. The low-molecular-weight esters have very pleasant odors and indeed are the major components of the flavor and odor aspects of a number of fruits. Although the natural flavor may contain nearly a hundred different compounds, single esters approximate the natural odors and are often used in the food industry for artificial flavors and …show more content…
For example alcohols react with acid anhydrides to form esters:
O CH3CH2OH Ethanol + O H3C O O CH2CH3 + CH3COOH Acetic acid
C C H3C CH3 O Acetic anhydride
Ethyl acetate
Acid chlorides form esters by reaction with alcohols.
O CH3CH2CH2OH 1-Propanol + H3C Cl Acetyl chloride C H3C O C O
CH2CH2CH3 + HCl
n-Propyl acetate
In the latter reaction, an organic base such as pyridine is usually added to react with the hydrogen chloride. A number of other methods can be used to synthesize the ester group. Among these are the addition of 2methylpropene to an acid to form t-butyl esters, the addition of ketene to make acetates, and the reaction of a silver salt with an alkyl halide.
O CH3CH2C OH + CH2 2-Methylpropene (isobutylene) CH3 C CH3 H+ O CH3 CH3 t-Butyl propionate O CH2 C O + HOCH2 Benzyl alcohol CH3 C OCH2 CH3CH2C O C CH3
Propionic Acid
Ketene
Benzyl Acetate
O CH3C O- Ag+ Silver acetate
+
CH3 BrCH2CH2CH CH3 1-Bromo-3-methylbutane
O CH3 CH3C O CH2CH2CH CH3 Isoamyl acetate
As noted above, Fischer esterification is an equilibrium process. Consider the reaction of acetic acid with 1butanol to give n-butyl …show more content…
The vapor is homogeneous, but when it condenses, it separates into two layers. The upper layer is composed of 11% alcohol, 86% ester, and 3% water, but the lower layer consists of 97% water with only traces of alcohol and ester. If some ingenious way to remove the lower layer from the condensate and still return the upper layer to the reaction mixture can be devised, then the equilibrium can be upset and nearly 100% of the ester can be produced in the reaction flask. The Dean Stark trap shown below is one method to solve this equilibrium
Synthesis of Methyl Benzoate by Fisher Esterification from K. L. Williamson, Macroscale and Microscale Organic Experiments, 2nd Ed. 1994, Houghton Mifflin, Boston p385 Revised 10/15/03
Prelab Exercise: Give the detailed mechanism for the acid-catalyzed hydrolysis of methyl benzoate. Introduction: The ester group is an important functional group that can be synthesized in a number of different ways. The low-molecular-weight esters have very pleasant odors and indeed are the major components of the flavor and odor aspects of a number of fruits. Although the natural flavor may contain nearly a hundred different compounds, single esters approximate the natural odors and are often used in the food industry for artificial flavors and …show more content…
For example alcohols react with acid anhydrides to form esters:
O CH3CH2OH Ethanol + O H3C O O CH2CH3 + CH3COOH Acetic acid
C C H3C CH3 O Acetic anhydride
Ethyl acetate
Acid chlorides form esters by reaction with alcohols.
O CH3CH2CH2OH 1-Propanol + H3C Cl Acetyl chloride C H3C O C O
CH2CH2CH3 + HCl
n-Propyl acetate
In the latter reaction, an organic base such as pyridine is usually added to react with the hydrogen chloride. A number of other methods can be used to synthesize the ester group. Among these are the addition of 2methylpropene to an acid to form t-butyl esters, the addition of ketene to make acetates, and the reaction of a silver salt with an alkyl halide.
O CH3CH2C OH + CH2 2-Methylpropene (isobutylene) CH3 C CH3 H+ O CH3 CH3 t-Butyl propionate O CH2 C O + HOCH2 Benzyl alcohol CH3 C OCH2 CH3CH2C O C CH3
Propionic Acid
Ketene
Benzyl Acetate
O CH3C O- Ag+ Silver acetate
+
CH3 BrCH2CH2CH CH3 1-Bromo-3-methylbutane
O CH3 CH3C O CH2CH2CH CH3 Isoamyl acetate
As noted above, Fischer esterification is an equilibrium process. Consider the reaction of acetic acid with 1butanol to give n-butyl …show more content…
The vapor is homogeneous, but when it condenses, it separates into two layers. The upper layer is composed of 11% alcohol, 86% ester, and 3% water, but the lower layer consists of 97% water with only traces of alcohol and ester. If some ingenious way to remove the lower layer from the condensate and still return the upper layer to the reaction mixture can be devised, then the equilibrium can be upset and nearly 100% of the ester can be produced in the reaction flask. The Dean Stark trap shown below is one method to solve this equilibrium