Fischer Esterification

Sabrina(Jingyao) Liao

Purpose

The purpose of this experiment is to synthesize isopentyl acetate using the Fischer esterification procedure. Techniques used include: reflux, liquid-liquid extraction, distillation

Mechanism

Table of reactants and reagents 

Reactant/ reagent	amount	moles	Molar mass	density	bp/mp	comment
Isopentyl alcohol	15ml	0.140 mol	88.148 g/mol	0.8247 g/cm3	130.5 celcius/-117.2 celcius	reactant
Glacial acetic acid	20 ml	0.350 mol	60.052 g/mol	1.05g/cm3	118-119 celcius/ 16-17 celcius	reagent
Sulfuric acid	4 ml	0.0746 mol	98.079 g/mol	1.83 g/cm3	337celciu/10celcius s	reactant
Sodium bicarbonate	25 ml	0.655mol	84.007 g/mol	2.2g/cm3	851 celciu/ 50 celcius	Neuturatlize reaction
Sodium chloride	10 ml	0.4551 mol	58.44 g/mol	2.16g/cm3	11465°C celcius/ 800.7°Ccelcius	Extraction
Magnesium sulfate	2 scoops	N/A	120.366 g/mol	2.66 g/cm3	330 celcius/ 1124 celcius	Drying agent

Mass of empty veil:  13.256 g

25 ml round bottom flask: 28.289 g

Calculations

Isopentyl alcohol no. of mol: (15ml x 0.8247 g/ml)/  88.148 g/mol = 0.140 mol

Glacial acetic acid  no. of mol: (20ml x 1.05g/ml) / 60.052 g/mol=  0.350 mol

Sulfuric acid no. of mol: (4ml x 1.83 g/ml) / 98.079 g/mol= 0.0746 mol

Sodium bicarbonate no. of mol: (25 ml x 2.2g/ml)/ 84.007 g/mol= 0.655mol

Sodium chloride no. of mol: (10ml x 2.66 g/ml) / 58.44 g/mol= 0.4551 mol

Procedure:  

15 ml of isopentyl alcohol and 20 ml of glacial acetic acid were obtained into a 100 ml round bottom flask with a magnetic stir bar. The mixture was cooled down through an ice bath for around 3 minutes, followed by 4 ml of concentrated sulfuric acid added to the mixture and swirled afterward. The mixture was then refluxed for about 45 minutes using a reflux apparatus. The mixture inside the flask illustrated dark brown color as the reaction proceeded. The mixture was heated at around 50 degrees Celsius and stirred by a stir plate at the speed of 380 RPM. After being refluxed, the mixture inside the flask was transferred into a separatory funnel, followed by 50 ml of water added inside. After being swirled, the bottom layer of the mixture was drained off. The remaining layer was then washed twice with 25 ml sodium bicarbonate each time. The mixture was rinsed again with 25ml water after shaking the mixture up and down three times, and 10 ml of sodium chloride was added to the mixture. The mixture was then swirled thoroughly, the bottom layer was drained into a beaker labeled as aqueous waste while the top layer was collected into an Erlenmyer flask and dried with two scoops of magnesium sulfate. The product was then filtered into a  50ml round bottom flask with a glass funnel with filter paper in it. After that, the filtered product was then distilled into a 25 ml round bottom flask with a distillation apparatus. Eventually, the product was transferred into a labeled veil. 

Table of products

products	yield(g)	Yield (mol)	Theoretical yield (g)	Molar mass	Percent yield	Theoretical mp/bp	Experimented BP	density
Isopentyl acetate (banaa oil)	10.086 g	0.0775 mol	18.2 g	130.19g/mol	55.4%	-78 celcius / 142 celcius	141 celciusQ	0.876g/cm3

Calculation

Yields of Isopentyl acetate = 23.342g- 13.256g(mass of empty veil with lid)= 10.086 g

Isopentyl acetate yielded no. of mol: 10.086g/ 130.19 g/mol  = 0.0775 mol

Theoretical yield of Isopentyl acetate: theoretical mass=0.140 mol (same no. of mol as isopentyl alcohol) x 130.19 g/mol= 18.2 g

Percent yield: %= 10.086 g/18.2 g= 0.554 =55.4%

Discussion

The IR spectrum of both reactants and products are as below (Figure 1 & 2). IR spectrums of reactants can be differentiated based on key functional group peaks. In the top diagram of Figure 1, as labeled in the diagram, a sharp peak is observed at 3317. 03 cm^-1. This illustrates the presence of the OH group in isopentyl alcohol. The bottom diagram, on the other hand, illustrated a broad OH peak of carboxylic acid at 3017.11 cm^-1, which is absent on the top diagram. Besides, there’s also a prominent peak at 1703.44 cm^-1 which indicates the existence of the carbonyl group a carboxylic acid. The carbonyl group peak in the acetic acid shows up at 1703.44 cm^-1 while the carbonyl group peak in isopentyl acetate appears at 1739.18 cm^-1. I assume the shift is caused by the influence of the oxygen right next to the carbonyl group in the ester. Based on the diagrams, it is obvious that the carboxylic acid has been converted to an ester since the carbonyl group peak shifted from 1703.44 cm^-1 to  1739.18 cm^-1 as I just discussed. Besides, the ester functional group also illustrates a peak at 1387.58 cm^-1 due to the CO stretch. In conclusion, isopentyl acetate was successfully synthesized and this was confirmed by the IR spectrum of the reactants and products.

Fig 1. IR spectrum of starting material

Fig 2. Experimented product IR spectrum

Works Cited

PubChem. “PubChem.” Nih.gov, National Library of Medicine, 2022, pubchem.ncbi.nlm.nih.gov/.