CHEM 6BL Lecture Notes - Lecture 9: Isoamyl Acetate, Acetic Acid, Isoamyl Alcohol

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ochregiraffe39

25 Apr 2018

School

UCSB

Department

Chemistry and Biochemistry

Course

CHEM 6BL

Professor

Gainer

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The purpose of this experiment was to synthesize a fragrant ester via the fischer esterification. Esters are formed through condensation reactions between a carboxylic acid and an alcohol. However, when this reaction is catalyzed by an acid, it is called a fischer esterification. To synthesize isoamyl acetate, a fragrant ester, smelling like banana, first 1. 6ml of. Isoamyl alcohol was added to a 5. 0ml conical vial along with a spin vane. The vial was weighed before adding the alcohol and found to have a mass of 24. 3g and weighed again with the alcohol to have a mass of 25. 171g, thus the starting mass of alcohol used was 0. 871g. In the fischer esterification reaction the limiting reagent is the alcohol and thus an important component to the reaction. The spin vane acts similarly to a boiling stone in that it keep the reaction from bumping and allows for a rolling boil necessary for reflux. 2-3 drops of concentrated sulfuric acid was added.

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Can anyone tell me how to get the percent and theoretical yield here?

- 2129 11 W- CH 4521-6: Fischer Esterification Introduction Esters are among the most widespread of all naturaly liquids that are responsible for the pleasant odors of fruits and flowers. Examples are ethyl cinnamate, whic occurring.compounds. Many simple esters are fragrant Ts the smell of cinnamon, and isobutyl acetate, contributing to the aroma of cherries, raspberries and of giycerol and fatty acids Esters are characterized by having the functional group:RO.R,where Escher esterification. This reaction refluxes a carboxylic acid inan . However, the most common esters found in nature are fats and ble oils, which are esters a carbon is double-bonded to one alcohol, creating the ester plus water as oxygen atom and sin The most classic method for creating an ester is the products: estor orer alcohai +R-OH catalyst A strong acid, traditionally sulfurits acid, is used as a catalst. Since the reaction is at equilbrium, simply reacting one mole of asid with one mole of alcohol will give a mixnture of starting materals and yield of the product may be improved using le Chatelier's principle: . Using the alcohol as a solvent (le. arge excess wil hlp push the equllbrium to the right By sequestering water (a reaction product), the equilibrium is pushed to the right. The use of a solvent which forms low-bolling azeatropes with water, such as toluene, in conjunction with a Dean-Stark apparatus has a similar effect, as is the use of other drying agents like molecular sieves Since low molecular weight esters typically have lower boling points than their parent carboxylic acids and alcohols because they are not able to form hydrogen bonds, the ester products may be distilled out of the reaction vessel as they are formed. By removing the ester product in a reactive distillation, the equilibrium once again lies to the righ For today's experiment, you will be able to choose which sweet-smelling ester you want to make. The table of reactants below gives you an idea of the range of smells. An ester will esterification reaction. This reaction involves mixing an alcohol with a carboxylic acid to form an ester and water. The reaction is reversible and an example is shown below be synthesized using the Fischer catalyst acetc acid propanopropyl acetate (pear) 47

Draw a complete arrow pushing mechanism for the Fischer esterification reaction being performed in this lab. Use highlights (with pen, marker, crayon, highlighter, etc) in your mechanism to illustrate whether the oxygen bonded to the butyl group in the product originates from the carboxilix acid or from the alcohol starting material

1) Draw a complete arrow pushing mechanism for the pivaloylation experiment. Use 'R-OH' as the alcohol in your mechanism.

2) Draw a "to-scale" replica of thge TLC plate that you will be preparing for the competition experiment. Which would you expect to be found higher up on the silica plate during TLC analysis -- the alcohol strating material or the ester product? Explain your answer.

CHEM 6BL Lecture Notes - Lecture 9: Isoamyl Acetate, Acetic Acid, Isoamyl Alcohol

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