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Oxidation of Isoborneol & Reduction of Camphor Author: Jennifer Lopez Reviewer: Tabby Sanders Editor: Vivi Venegas CH 238- SX

Introduction In organic chemistry, carbonyl compounds are oxidized by primary and secondary alcohols. There are many reagents that are used to complete this reaction but some of them are harmful humans as well as the environment. The common reagents that can be used but are toxic include CrO3, Na2CrO7, and KMnO4. However, there are oxidizing agents that are safer, and less harmful to the environment called, green oxidizing agents. Household bleach is one of the green oxidizing reagents and can be used to oxidize isoborneol into camphor. First, by forming HOCl with acidic treatment. The purpose of this experiment was to use bleach to oxidize isoborneol into camphor, determine how well of an oxidizing agent bleach was, and to analyze ow much yield bleach could produce. This experiment also tested how well NaBH4 would reduce camphor and to find the yield NaBH4 would produce. Melting point analysis and IR data was done to show how pure the product was as well has how efficient the reducing and oxidizing agents worked together. The mass of the initial product and the mass of the produced product was used to find the percent yield. Finally, a 1H-NMR was done to compare if isoborneol’s theoretical ratio produced and the amount of borneol produced from the reduction was actually seen in our chemical reaction done in lab. In order to perform the reaction to produce camphor from isoborneol and bleach, the bleach had to be treated with an acid to for HOCl in which is the actual oxidizing agent. Shown below in figure 1 is the mechanism for this reaction and in equation 1 is the balanced equation for this reaction. Figure 1. Equation 1. Balanced equation for the mechanism above.

NaOCl + CH3COOH à HOCl + CH3COO- H+ Then, the HOCl formed from the bleach and acid oxidizes the isoborneol to produce camphor as shown in the mechanism below labeled figure 2, along with the balanced equation labeled equation 2. Figure 2. Mechanism of HOCl and isoborneol. Equation 2. Balanced equation for the mechanism shown above.

C10H18O + 2 HOCl à C10H16O + 2 H3O+ + 2 Cl-

Finally, to reduce camphor, a reducing agent such as NaBH4 and water was added. NaBH4 provides hydride ions that can either attack camphor from the top or bottom. This is called a top face attack and a bottom face attack. The mechanism for a top and bottom face attack is shown below in figure 3, 4, and 5 below. Figure 3. Figure 4. Mechanism of the top face attack Figure 5. Mechanism for the bottom face attack Equation 3. The balanced equation for this reaction:

4 C10H16O + NaBH4 + H2O à 4C10H18O + H3BO3 + NaOH Oxidation and reduction is a major part of this experiment along with the concept of producing a major and minor product. Oxidation results in the loss of electrons and reduction results in the gaining of electrons. In the reaction oxygen starts off being a part of an alcohol group and results in becoming a part of a carbonyl group. This results in oxygen being oxidized as it gains a pair of electrons when a double bond is formed. When the oxygen is part of the carbonyl group, he double bond breaks and two single bonds are formed, it is getting reduced. In this reaction when the oxidation of isoborneol happens, the compound gets oxidized as the double bond to oxygen is formed. When the camphor is transformed back into borneol and isoborneol, the oxygen is getting reduced as the double bond is broken and oxygen becomes alcohol. The final concept to look at in this experiment is the formation of the major and minor product. As the camphor is reduced the hydride can either attack on the top face or the bottom face producing two possible products such as isoborneol or borneol. In this reaction, hydride attacks where there is the least steric hindrance and since borneol and isoborneol both have two methyl groups on the top face, it will attack the bottom face to form isoborneol. Isoborneol will form faster and will produce more product than borneol because it takes less energy, making it the major product. Other methods used during this experiment include the use of a separatory funnel, usage of a drying agent, melting point analysis, and IR and 1H-NMR analyses. A separatory funnel was used for the process of oxidizing isoborneol into camphor. The piece of glassware separates the components of a mixture into two immiscible solvent phases of different densities and was used for isolating the product that was contained in the ether layer from the aqueous layer. A drying agent was also used to remove excess water that could have mixed with the ether layer during the separation. To test the purity of the products produced during the experiment, the melting point of camphor and isoborneol and borneol mixed was analyzed to assess how pure the products were. If the product contained impurities the melting point range would be substantially larger

than the compounds true melting point. Finally, IR and 1H-NMR analyses were performed on both of the products that were formed. IR was done to analyze if there was any excess reactant still left. The IR for isoborneol/borneol would result in a distinct –OH peak present but no carbonyl peak and the camphor would have a distinct carbonyl peak but no –OH peak present. Lastly, 1H-NMR was performed to calculate the rations of which isoborneol and borneol were synthesized by the reduction of camphor. The reagents used during this experiment are included in table 1 below.

Table I: Table of Reagents1 Name

MW (g/mol)

M.P. (Celsius)

B.P. (Celsius)

Density (g/cm3 )

1543.253

212

213

1.01

74.44

18

101

1.11

MgSO4

120.366

1124

>1124

2.66

Camphor

152.23

175

209

0.990

Diethyl ether

74.12

-116.2

34.6

0.713

NaHCO3

84.007

50

854

2.20

Acetic Acid

60.052

16.6

118.1

1.05

Na2SO4

142.04

884

1429

2.66

NaBH4

37.83

400

500

1.07

Water

18.02

0

100

1.00

Isoborneol/Borneol NaOCl (bleach)

Experimental Part A: First, .511 g of stock Isoborneol was weighed out on a scale and dissolved in 1.5 mL of glacial acetic acid in a 25 mL Erlenmeyer flask. Then 4.0 mL of household bleach was added to the flask. The flask was swirled until it became warm and a white precipitant formed. Over the next 10 minutes the flask was occasionally stirred, and after 10 minutes, the solution was dropped on wet starch iodine paper. The iodine paper was expected to turn blue, indicating

excess NaOCl, meaning the starch iodine complex was formed. This was done and the starch iodine test gave a positive result. The solution was then diluted with 15.0 mL of water and transferred into a separatory funnel. After the solution was transferred into the funnel 15.0 mL of diethyl ether was added along with 1.0 mL of saturated NaHSO3 to reduce any excess NaOCl. The starch iodine test was done again to confirm that excess unreacted NaOCl was not present. The test was performed until the test was negative. The separatory funnel was then shaken and then vented to release any pressure and placed on the ring stand so the layers could form and separate. After the layers were separated, the aqueous layer was removed into a beaker. After the aqueous layer was removed, the ether layer was washed with 10 mL of saturated NaHCO3 and tested with litmus paper to make sure it was basic. Since our ether layer was not yet basic, another 10 mL of NaHCO3 was added and tested again. Once the test was basic, the ether layer was dried with anhydrous Na2CO4. Once the ether layer was dried it was decanted into a clean dry 25 mL beaker that had been weighed. The flakwas then placed into a warm water bath at the approximate consistent temperature of 42°. The temperature of the warm water bath was taken and monitored with an electric thermometer. The flask stayed in the warm water bath until the solution evaporated and a camphor was formed. Once the solid was formed the flask was placed on the scale and weighed to determine the percent yield of camphor formed. IR spectra and melting point analysis was then done to determine the purity of the camphor.

Part B: To tart the reduction of camphor, .113g of camphor from part A was weighed out on a scale and transferred to a 10 mL Erlenmeyer flask. Then, .5 mL of methanol was added to the 10 mL flask and stirred with a stir rod until the solid was completely dissolved. Once the solid was dissolved, 104 g of NaBH4 was weighed out on a scale and carefully transferred to the flask in 4 portions while simultaneously swirling the flask. Once all the NaBH4 was added, the solution was heated in a warm water bath at approximately 63° to boil for two minutes. The temperature of the warm water bath was monitored and taken with an electric thermometer. The solution was then removed from the warm water bath and cooled for several minutes. Once the solution was cooled, 3.5 ml of ice water was added and a solid was formed. The solid was then collected by suction filtration and dried on the filter for several minutes and transferred to a 10 mL Erlenmeyer flask. Then 4.5 mL of ether was added to the flask to dissolve the product and anhydrous MgSO4 was added to dry the solution. The MgSO4 was then filtered away from the solution, which was placed into a dry, clean, and weighed 25 mL Erlenmeyer flask. The original 10 mL flask was then rinsed with 1 mL of ether and filtered into the 25 mL flask. The 25 mL flask with solution was then placed into a warm water bath at the temperature of approximately 42° until the ether was evaporated and solid was formed. Once the ether was evaporated the 25

mL flask was weighed again to obtain the percent yield. The solid product of isoborneol and borneol formed was then used for melting point analysis as well as IR spectra to determine how pure the substance was. The rest of the product was then placed in a tube for storage and given to a lab TA to perform 1H-NMR to determine the ratio of isoborneol and borneol that was formed.

Results: The data table for the masses measured during the formation of camphor and the formation of isoborneol are shown Table 2 and Table 3. Table II: Mass Table for Formation of Camphor Mass of Isoborneol used

0.511 grams

Mass of empty vial

31.990 grams

Mass of vial with product

32.305 grams

Final mass of product

0.315 grams

Table III: Mass Table for Formation of Isoborneol Mass of Camphor used

0.100 grams

Mass of empty vial

25.9 grams

Mass of vial with product

26.0021 grams

Final mass of product

0.1021 grams

Equation 4 is used to calculate the experimental yield of camphor and isoborneol. The theoretical yield formula is shown in equation 5. Equation 6 is a combination of equation 4 and equation 5 and is used to calculate the percent yield. Experimental Yield Flask with product (grams) - empty flask (grams)= product (grams) Camphor: 32.305 grams - 31.990 grams= 0.315 grams Isoborneol: 26.0021 grams - 25.9 grams= 0.1021 grams Theoretical Yield

Equation 4.

Equation 5.

grams of product mole of product Moles of Limiting Reagent x x mole of limiting reagent mole of product 1 1mol of camph∨¿ 152.23 g of camp h∨¿¿ ¿ x¿ 1 mol of camp h∨ Camphor: 1 mole of Isoborneol 1mol of Isoborneol 0.511 g of Isoborneol x¿ x 154.25 g of Isoborneol 1 = 0.504 grams of Camphor 154.25 g of Isoborneol 1 mol of camp h∨¿ x 1 mol of Isoborneol 1mol of Isoborneol 152.23 g of camp h∨¿ x ¿ Isoborneol: ¿ 1mol of camph∨ ¿ ¿ 0.100 g of Camp h∨ x ¿ 1 ¿ = 0.101 grams of isoborneol Percent Yield Experimental Yield x 100 T h eoretical Yield

Equation 6.

0.315 grams x 100=62.5 % 0.504 grams 0.1021 g r ams x 100=101.09 % Isoborneol: 0.101 grams Table 4 lists the experimental and original melting point in degrees celsius for both camphor and isoborneol. For camphor the experimental melting point was 151.7 C, while the literature melting point is 175 C. The experimental melting point for isoborneol was not written down, but the literature melting point is 212 C. Figure 5 shows the IR spectrum for isoborneol produced from the reduction of camphor. The spectrum does not show any broad stretching, the only stretching shown is in the fingerprint region. Figure 6 shows the IR spectrum for camphor synthesized from the oxidation of isoborneol. The spectrum shows broad stretching around 3400 cm-1 and narrow stretching around 2800-2700 cm-1 as well as stretching around 1700 cm-1. Figure 7 shows the NMR spectrum for isoborneol produced from the reduction of camphor. Table 4: Melting points comparison Camphor:

Name

Experimental MP ( C)

Book MP ( C)

Camphor

151.7

175

Isoborneol

----

Figure 5: IR spectrum from de reduction of camphor

212

Figure 6: IR spectrum from the oxidation of isoborneol.

Figure 7: NMR spectrum from the reduction of camphor

Discussion: Part A of this experiment was to oxidize isoborneol in order to create camphor by using household bleach. After camphor was produced, a melting point was taken, to test the purity of the product. The experimental melting point of camphor, listed in table 4, was 151.7 C, while the literature melting point was 175 C. There is a large difference between the melting point of the product and the melting point of pure camphor, impurities in the product synthesized could

be the cause of this. Next, the IR was performed on the product and shown in figure 6. The distinct peaks around 3400 cm-1 is most likely due to unreacted isoborneol or other impurities present in the compound. Stretching shown around 2800-2700 cm-1 represents carbon-hydrogen sp3 bonding. The peak round 1700 cm-1 indicates the presence of a carbon-oxygen double bond, most likely due to camphor since it has a carbonyl group. In Part B of the experiment, camphor was reduced to produce isoborneol as well as some borneol. These are conformational isomers and the formation of each depends on how the hydrides attack the six-membered ring. The experimental melting point for isoborneol was not taken, the literature melting point of 212 C is found in table 4. As a result of not taking the melting point, it was not possible to test how pure the substance created was. In future labs care will be taken to take the melting point of the product created. Figure 5 shows the IR that was performed for the product of the reduction of camphor. In the IR there is no notable distinct peaks, the only stretching is in the fingerprint region, which is generally ignored. No IR stretching present. This should be due to a number of experimental errors, for example not separating the ether from the drying agent. This could cause the ether along with the product that should have been formed to boil away, instead leaving the drying agent, which would create an IR spectrum with not stretching. The amount of solid produced for the second part was a greater amount than the expected value, indicating the camphor obtained initially was greater than one gram and or the ether was not filtered from the drying agent.

Conclusion: The goal of this experiment was to oxidized isoborneol to create camphor. warned how to oxidized isoborneol in order to create camphor and after we reduced camphor to create isoborneol into a mix of isoborneol and borneol. During this experiment the use of IR analysis was done to confirm the identity of each compound synthesized during the experiment.. Even though we had some errors happening during the lab, isoborneol’s identity was found stronger and it showed up better on the IR results. On the other hand the product’s amount was odd during the second part of the lab, which made the IR spectrum come with almost no compound in it, resulting the peaks not showing. To make this lab better, the students should have a better understanding of each compound's property, and showing how to do the experiments a little bit more detailed and this will rbing better results when performing the techniques.

Where is the discussion for 1H-NMR it needs to be included or the error as to why we didnt get one needs to be included. It needs to include why it was done such as to find the ratio of isoborneol to borneol produced. And the ratio needs to be included

References 1. N/A. “PubChem.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, pubchem.ncbi.nlm.nih.gov/. 2. Brown, William H.; Brent L. Iverson; Eric V. Anslyn; and Shristopher S. Foote. Organic Chemistry. 7th ed. N.p.: Mary Finch, n.d; Print. 3 .WebMD. http://www.webmd.com/vitamins-supplements/ingredientmono-709CAMPHOR.aspx?activeIngredientId=709&activeIngredientName=CAMPHOR (accessed June 2019)

Questions: 1. How many chiral carbons are present in camphor? Based on your answer, how many stereoisomers are possible for camphor? There are two chiral centers present in camphor, therefore camphor will have four stereoisomers.

2. Below are the structures for borneol and isoborneol. Give the configuration of the carbons indicated by *. What’s the stereochemical relationship between borneol and isoborneol? Borneol and isoborneol are diastereomers....