Sythesis of Isopentyl Acetone Banana Oil Lab Report PDF

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Summary

LAB REPORT...

Description

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Synthesis of Isopentyl Acetate: Banana Oil Purpose The purpose of this experiment was to synthesis isopentyl acetate (banana oil) from the reaction of isopentyl alcohol with acetic acid by performing fischer esterification. The techniques used in this experiment include: refluxing, extraction, separation, filtration, boiling point, and simple distillation. We used proton n uclear magnetic resonance spectroscopy (1H NMR) and infrared spectroscopy (IR) to confirm the identity of our final product.

Reaction Scheme

Mechanism

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Procedure The procedure was followed as is described in the Wissinger Manual1 . Some deviations from the manual included washing with sodium bicarbonate twice instead of once in order to obtain an appropriate pH. Also, the mixture was distilled at 70 on the variac outlet instead of the 45 stated on the manual.

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Reagents Table Acetic Acid

Isopentyl Alcohol

Isopentyl Acetate

Sulfuric Acid

Molecular Weight (g/mol)2

60.05

88.15

130.2

98.08

Grams (g)

8.917

5.0

3.1

2.208

Mols

0.149

0.057

0.024

0.023

mL

8.5

6.18

3.54

1.2

Density (g/ml)2

1.049

0.809

0.876

1.840

Boiling Point (℃)2

118.1

130

143

290

Melting Point (℃)2

16.7

117

78

0

Solubilities2

Miscible

Miscible

Insoluble

Miscible

Hazards2

Flammable

Corrosive

Flammable

Corrosive

Results and Observations Observations: In the first part of the reaction while refluxing, sulfuric acid was added to the acetic acid and isopentyl alcohol solution and the solution turned a brownish pink color. During the reflux the solution got darker as the reaction progressed and began to have a banana smell. Next in the separatory funnel there were a series of washes in order to extract the isopentyl acetate from the mixture. Sodium bicarbonate was added to neutralize the acid. During this step in the experiment the solution had bubbles of air due to the production of carbon dioxide from the sodium bicarbonate and thus needed to be vented out. Litmus paper was used to make sure all the acid

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was removed from the solution before distillation. In this experiment the litmus paper turned a green color which indicated the solution had a basic pH, which was around 9 and was ready to begin distillation. However, the solution contained excess water that was removed with MgSO4 drying agent before distillation. The solution was dried appropriately when MgSO4 did not clump up when more was added and the solution turned clear. When the solution was transferred to the distillation apparatus it had a dark brown color with a distinct banana odor. After distillation the solution turned clear and the banana smell got stronger.

IR Spectrum of Compound A (Neat Sample): *Compound A

Bond Vibrations

Frequency (cm-1)

Intensity

A

Carbonyl overtone

3463.5

Weak

A

C-H sp3 stretch

2958.7

Strong

A

C=O non-conjugated ester stretch

1742.1

Strong

A

C-H sp3 bend (CH2)

1466.6

Medium

A

C-H sp3 bend (CH3)

1367.3

Strong

A

C(=O)-O ester stretch

1243.2

Strong

*Compound A is Isopentyl Acetate. 1

H NMR (300 MHz, CDCl3) of Compound A: Protons, Hx

Chemical Shift, ppm

Splitting Pattern

J value, Hz

Integration Area (cm)

Relative #H’s

Ha

0.908

Doublet

6.6

9.8

6

Hb

1.514

Quartet

6.9

3.3

2

Hc

1.675

Multiplet

6.9

1.8

1

5

Hd

2.033

Singlet

----

4.6

3

He

4.084

Triplet

6.9

3.3

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Product Table: Theoretical Actual Yield Yield

% Yield

Corrected Yield

Bpt. Range

Literature2 Bpt.

Appearance

7.42 grams

41.8%

40.9%

128℃-132℃

142℃-145℃

Colorless liquid, clear, and smells like bananas.

3.1 grams

Discussion/Conclusion

The reaction with 8.5 mL of acetic acid with 5.0 g of isopentyl alcohol underwent fischer esterification using sulfuric acid as a catalyst. This reaction yielded 3.1 g of isopentyl acetate, also known as banana oil and water as a by product. The percent yield the product isopentyl acetate was 41.8 percent with a 97.9 percent purity and 40.9% corrected yield.

The main analysis used to identify the identity of the product was 1 H NMR. The solvent used was deuterated chloroform (CDCl3). There were a total of five types of protons, Ha , Hb, Hc, Hd, and He, identified that belonged to the product, isopentyl acetate. There was one peak associated with a reaction caused by the solvent used which denotes the protons in CHCl3. Also there were faint peaks associated with the protons on the starting material of isopentyl alcohol (A′). The first proton identified on the spectrum, Ha , according to the n+1 rule was a doublet with only 1 neighboring proton which was the proton in Hc. On the isopentyl group, Ha, can be attributed to

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the two methyl groups containing a total of 6 protons that are the farthest away from the electronegative oxygens. Therefore the Ha, is the group that was the most upfield. The next group identified was Hb, that is on the isopentenyl group but is a bit more downfield than the Ha group and contains two protons. Hb has a quartet splitting pattern with 3 neighbors which are the two  protons in He and the one proton in Hc. Juxtaposition to Hb on the 1 H NMR spectrum is Hc with only one proton but has a splitting pattern of a multiplet, specifically a nonet with 8 neighboring hydrogens. The 8 neighboring hydrogens are from the 6 protons in Ha and the 2 protons in Hb. Both Hb and Hc are located on the isopentyl group and are upfield. These groups are also shielded   because the electronegativity difference between the carbons and hydrogens is low.

The next series of proton types (Hd and He) are further downfield because they are deshielded due to the inductive effects of the oxygens on the ester and carbonyl. The proton type He lies near the ester which is the reason for being the most deshielded group of the isopentyl acetate. This proton group consists of two relative protons with a triplet splitting pattern and two neighbors which are from the two protons in Hb. The acetate group is identified by the methyl group with the proton type Hd. This group has a singlet with no neighbors because it is the farthest away from all the proton types. This group is more downfield because it is deshielded by the carbonyl group on the acetate.

The 1 H NMR method helped identify that this experiment produced the appropriate compound being isopentyl acetate, however there was an impurity found. The impurity was from the two protons near the alcohol group on the starting material, isopentyl alcohol. This was found because there were faint peaks located on the 1 H NMR at approximately 3.67 ppm. The protons

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on the carbon chain of the isopentyl alcohol group are very similar to the ones on the product, therefore would not change and in fact be superimposed to one another. Thus the only difference that would indicate that there is starting material in the product would be the protons near the alcohol group being A′. The purity calculations showed a 2.1 percent of isopentyl alcohol present in the final product where the 97.9 percent was the expected isopentyl acetate. Similarly, the solvent used to process the solution in the 1 H NMR, deuterated chloroform, is not a hundred percent effective and did shows up on the spectrum. It showed up as a singlet at about 7.27ppm that was from the CHCl3 protons. There were no significant peak associated with the protons in water on this 1 H NMR spectrum.

The other important method used was IR spectroscopy which was used to identify the functional groups of our product. The significant bond vibrations that confirmed that isopentyl acetate was the product obtained was the carbonyl nonconjugated ester stretch at 1742.1 cm-1  with strong intensity and C(=O)-O ester stretch at 1243.2 cm-1  with a strong intensity as well. These frequencies were within the expected literature range. The next series of bond vibrations were associated with the CH 𝛑 bonds on the isopentyl acetate. The sp3 CH stretch was at 2958.7 cm-1  with a medium intensity, this particular CH bond vibration can be attributed to the methyl group on the acetate group. The other two significant sp3 CH bends were associated the alkane with the  CH2 bend at 1466.6 cm-1  with medium intensity and the CH3 at 1367.3 cm-1  with a strong 

intensity. There was also a weak carbonyl overtone at 3463.5 cm-1  . On the IR spectrum there was no OH stretch was present at the expected range 3650-3550 cm-1  that would indicate that the alcohol from the starting material. However, through the 1 H NMR and the purity calculation

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there is confirmation that there was 2.1 percent of isopentyl alcohol present in our final product.

The final method used to analysis the identity of the product, isopentyl acetate, was experimental boiling point which was 128℃-132℃. This was compared to the literature value of 142℃-145℃. The experimental boiling point has a narrow range that indicates it was an accurate measurement and reflective of the isopentyl acetate. However, there is a slight deviation from the literature boiling point that can be attributed to kerosene thermometer that was used which is not as precise as a mercury thermometer.

Nonetheless the reaction of isopentyl alcohol with acetic acid yielded 3.1 grams of isopentyl acetate with an overall 41.8% yield. This was proved to have a 97.9% purity which indicates the techniques used were accurate and effective. However, there were sources of error that are important to note because they may have influenced the direction of the results. During the first sodium bicarbonate wash in the separatory funnel the cap flew out while venting and a small amount of the mixture spilled on the countertop. This incident may have contributed the decrease in the percent yield. In addition this experiment addressed two green chemistry principles that helped increase the efficiency of the reaction while minimizing waste in the environment. The first one is that the H2SO4 catalyst was used to speed up the reaction because they are superior to stoichiometric reagents3 . Likewise, this experiment provided an organic solvent free procedure which prevented waste.

Works Cited 1. Wissinger, J. E. Laboratory Manual for Organic Chemistry 2311, 12th ed. Fountainhead Press: Southlake, Texas, 2015, pp. 32-34. 2. www.chemspider.com

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3. https://www.acs.org/content/acs/en/greenchemistry

Appendix Determining Limiting Reagent 1 mol 8.5 mL × 1.049g/ml = 8.917g 60.05g = 0.149 mol of Acetic Acid

5.0g ×

1 mol 88.15g

= 0.057 mol of Isopentyl Alcohol → This was the limiting reagent.

Yield Calculations: Theoretical Yield 0.057 mol Isopentyl acetate ×

130.2g 1 mol Isopentyl acetate =

% Yield 3.1g 7.42g

× 100 = 41.8 % Isopentyl acetate

Purity Calculations Isopentyl Acetate (Hia): Ha= 9.8cm/6 = 1.63 Hb= 3.3cm/2 = 1.65 Hc= 1.8cm/1 = 1.8 Hd= 4.6cm/3 = 1.53 He= 3.3cm/2 = 1.65 Hia= 1.65 x 130.2 g/mol = 215.09g

7.42 g of Isopentyl acetate

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Isopentyl Alcohol (A′) A′: 0.1cm/2 = 0.05 x 88.15g/mol = 4.41 g % Purity 215.09g ÷ (215.09g + 4.41g) =

215.09g 219.5g

x 100 = 97.9%

Corrected Yield % Yield x % Purity = 0.418 x 0.979 = 0.409 → 40.9 % corrected yield 1H NMR J-value Sample Calculation Ha= (0.919 ppm - 0.867 ppm) 300 MHz = 6.6 Hz...