Creating a Greener Organic Chemistry Lab

Rojas 1

Bethel College

Creating a Greener Organic Chemistry Lab

Jose A Rojas

05/19/2010

Chemistry 482 Senior Seminar

Table of Contents

1. Abstract3
2. Background4
3. Methods and Experiments7
4. Reagents7
5. Synthesis of Catalyst7
6. General Oxidation Reaction Procedures8
7. Oxidizing Reactions Using K-OMS-28
8. Oxidizing Reactions Using H-K-OMS-29
9. Oxidizing Reaction using recycled H-K-OMS-210
10. Oxidation using 0.4 g of H-K-OMS-2 by Organic Chemistry Class11
11. Apparatus and Procedure11
12. Results13
13. Discussion14
14. Conclusion17

References19

Acknowledgments20

Appendix121

I. Abstract

The purpose of this project was to develop a green lab that could be used for a lab period for students in Organic Chemistry. The goals were to find a catalyst that was less toxic than ones currently in use for the oxidations of alcohols to ketones and to complete the reaction and procedures needed for separation and purification within a three hour lab period. The lab developed is based on the oxidation of the alcohol 9-flurenol into the ketone form 9-flurenone. The catalyst originally used was a polymer-supported, and the time for the completion of the reaction was an hour plus the time needed for all the other procedures needed to isolate the ketone. Octahedral molecular sieves (OMS) have shown a great potential for the oxidative catalysis of alcohols. These kinds of catalysts were investigated earlier by the Bethel graduate Omar Hasan in his seminar project last year. He studied a number of different OMS-2 type catalysts. However, in order to reach the goals of a green lab catalyst K-OMS-2 and H-K-OMS-2 were used because of their low toxicity levels. The results of this study indicated that the H-K-OMS-2 catalyst was able to complete the oxidation reaction within 20 minutes, while the K-OMS-2 catalyst did not work favorably toward goals. The lab developed in this project proved to be successful as demonstrated by the very good results obtained by the Organic Chemistry II class which recently tested the laboratory procedure.

II. Background

Omar Hasan, a bethel grad, in his undergraduate research worked with different catalysts that enhanced the oxidation of alcohol into ketones and aldehydes. Hasan was working with OMS-2, a porous manganese oxide octahedral molecular sieve. It is called OMS-2 because it has a 2x2 octahedron crystalline structure. Hasan indicated that the porosity of the OMS-2 give it the ability to channel some of the positive charges for superior catalytic activity. Figure 1, shows the structure of OMS-2. The OMS-2 channels have porous openings of 4.6Å. The OMS-2 structures are comprised of units of octahedron. OMS-2 consists of manganese oxide, , that share corners and edges that line up forming the octahedron. Even though, OMS-2 serves as a highly active thermally stable catalyst when ion exchanged with other metal ions, for example, vanadium and nickel, we will focus on the original form of OMS-2 (K-OMS-2) and on the hydrogen doped form of the OMS-2 (H-K-OMS-2). The hydrogen doped form is achieved by washing the K-OMS-2 with 1.0 M. By doping OMS-2, Hasan indicated that this significantly enhanced the conversion of alcohols to either the ketone or aldehydes form, which suggested that the oxidation was enhanced by Bronsted acid sites1. In figure 3, there is a list of the conversion of several alcohols and their conversion percentages when using the acid doped form of OMS-2, as well as, the original form K-OMS-2. The proposed oxidation mechanism for these oxidation reactions is illustrated in figure 2. Hasan also mentioned that H-OMS-2 and K-OMS-2 apart from being very stable catalyst that they can be store and be active for up to two years. Hasan found that these oxidizing reactions ended up as liquid products which eventually were analyzed by gas chromatography taking a very long time; this technique was use for qualitative purposes.

The search for greener catalysts that can oxidize reactions is becoming more and more popular today. In experiment 14 of the book Green Organic Chemistry2, the focus is on oxidation chemistry, where a secondary alcohol, 9-flurenol, is oxidized into its ketone form, 9-fluorenone, by using a polymer containing a reactive form of as their oxidizing agent. Figure 4 shows the reaction. The polymer-supported oxidizes organic substrates very readily. In the introduction to the lab, it mentions that typical oxidizing agents are often corrosive, toxic, and environmentally damaging, and that the development of environmentally benign procedures for the adjustment of oxidation state remain an important research goal2. In their lab, the experiment calls for refluxing the reactions, thin-layer chromatography (TLC) for checking the progress of the reaction as well as for qualitative and quantitative analysis, rotary evaporation of the solvent and the recrystallization and melting point determination for qualitative analysis. The procedure used 1 gram of the alcohol and 5 g of the dry polymer-supported catalyst to 35 ml of toluene in a 100 ml round bottom flask containing a magnetic bar. It was refluxed for about an hour while stirring and the reaction was check by TLC on silica plates for completion. Reaction was cooled to room temperature, filtered to remove the catalyst, removed the solvent with a rotary evaporator and weighted the crude product. Finally, recrystallyzed the crude product with a mixture of ethanol and water, weighted the recrystallized product and took the product’s melting point. The catalyst can be treated and stored ready to be reused.

Green chemistry is becoming the most popular way of doing chemistry. In order to do Green Chemistry, one or more of the twelve principles of green chemistry need to be follow when doing an experiment. For example, in order to achieve the goal of creating a greener lab some of these principles had to be followed. The followings are green chemistry principles provided by the Environmental Protection Agengy (EPA) website that were followed through this project: preventing waste, less hazardous chemical syntheses, designing safer chemicals, design for energy efficiency, catalysis and real-time analysis for pollution prevention. By combining the OMS-2 catalysts that Hasan studied with following the procedures and using the reagents that were used in experiment 14, in the book of Green Organic Chemistry, the goal for this project to develop a “Green Lab”. The reaction needed to be completed in less than a three hour period, so that this lab could be used during a lab period for the Organic Chemistry class in Bethel College. This project focused on using Hasan’s greenest catalyst which includes the doped catalyst H-K-OMS-2 and the original form K-OMS-2. The oxidation reaction of 9-fluorenol to 9-fluorenone is expected to work since Hasan was able to get very good conversion percentages when oxidizing phenyl ethanol, as well, as benzhydrol with the doped OMS-2 form H-K-OMS-2 and K-OMS-2. It should be a noted that Hasan used a vanadium\ catalyst which in most cases had very high conversion percentages. However, for our purposes of a green lab, this form of catalyst will not work since vanadium is very toxic. In the experiment 14, they used a polymer-supported as their catalyst. itself is much more toxic than our manganese oxide octahedral sieves which help us achieved our goal of a green lab. Lastly, the catalyst use for this project should be tested to see if it can be recycled or not in order to favor our purposes to create a green lab.

III. Methods and Experiments

A. Reagents

All reagents used were analytical grade and purchased from SIGMA-ALDERICH chemical supplier. Ultrapure deionized water (UDW) was used to prepare materials. Water was purified by a compact ultrapure water system by Barnstead.

B. Synthesis of Catalysts

1. K-OMS-2

4.3484 g. of was placed in a 100 ml beaker and dissolve in 75 ml UDW. 6.5272 g. of was placed in a 250 ml round bottom flask and dissolved in 22.5 ml UDW along with 2.3 ml concentrated . Then the initial solution of was carefully added to the solution. From this mixture a very dark mud like precipitate was precipitated. This mixture was reflux at about 100 for 24 hours. The product was vacuum filtered using a paper filter, washed with 7 small portions of UDW totaling 100 ml and dried at 120 overnight in an oven. After drying, the product was separated from the filter paper and ground to a powder by mortar and pestle. The product was then stored in a sealed glass vile. The final yield was 6.1140 g. of K-OMS-2.

2. H-K-OMS-2

0.9973 of the K-OMS-2 was exchanged with 200 ml of 1.0 M . This was done with vigorous stirring at room temperature for 2 hours. The product was then filtered by vacuum filtration and a paper filter. The product was vacuum filtered using a paper filter, washed with 7 small portions of UDW totaling 100 ml and dried at 120 overnight in an oven. After drying, the product was separated from the filter paper and ground to a powder by mortar and pestle. The product was then stored in a sealed glass vile. The final yield was 0.9284 g. of H-K-OMS-2.

C. General Oxidation Reaction Procedures

9-hydroxyfluorene (0.182 g.) and K-OMS-2 catalyst (0.4 g.) were refluxed with toluene (10 ml) in a round-bottom-flask (100 ml) containing a magnetic stir bar for 20 minutes. The reaction was followed every ten minutes by thin layer chromatography (TLC) on silica plates, developed with 30% acetone in hexanes. The reaction was cooled to room temperature; catalyst was removed by gravity filtration and washed with small amounts of toluene. Catalyst was dried and stored for future possible use of it. The solvent was removed by rotary evaporatorion. Small stream of air used to remove the last traces of the solvent. The crude product was recrystallized from a mixture of 50:50 ethanol/water and melting point determined.

D. Oxidation reactions using K-OMS-2

1. Experiment #1

9-hydroxyfluorene (0.1824 g) and K-OMS-2 (0.505 g) catalyst were added. The reaction was refluxed for about an hour and a half. The reaction was not completed after this time when it was checked by TLC. The recrystallize product was a white and yellow precipitate, nothing like our desire product, probably a mixture of starting materials and product.

2. Experiment # 2

9-hydroxyfluorene (0.1824 g) and K-OMS-2 (0.501 g) catalyst were added. The reaction was refluxed for about an hour and a half. The reaction was not completed after this time when it was checked by TLC. The recrystallize product was a white and yellow precipitate, nothing like our desire product, probably a mixture of starting materials and product.

3. Experiment #3 (using more catalyst)

9-hydroxyfluorene (0.182 g) and K-OMS-2 (0.2 g) catalyst were added. The progress of the reaction was followed every ten minutes by thin layer chromatography (TLC) on silica plates, eluting with 30% acetone in hexanes. The reaction never went to completion after the hour and a half, it seemed like the reaction was still going, and the spots in the silica plates looked like if there was a 50:50 mixture of starting material and product.

E. Oxidizing Reactions using H-K-OMS-2

1. Experiment #1

9-hydroxyfluorene (0.1823 g) and H-K-OMS-2 catalyst (0.05 g.) were added. The reaction was refluxed and stirred for about 40 minutes. After 40 minutes, the solvent was evaporated and we were unable to continue with the experiment.

2. Experiment #2

9-hydroxyfluorene (0.1827 g) and H-K-OMS-2 catalyst (0.0505 g.) were added. The reaction was not complete when checked with TLC after an hour and a half of refluxing. The recrystallized product was a light yellow precipitate with a melting point range of 104-118. The wide melting point range indicates impurity and that it is probably a mixture of starting material and product. The recrystallized product weighted 0.0737 g. with a percent yield of 40.79%.

3. Experiment #3 (using more catalyst)

9-hydroxyfluorene (0.1824 g) and H-K-OMS-2 catalyst (0.2 g.) were added. The reaction was complete after an hour and a half and the solvent had a yellow color. The recristallized product was very fine yellow crystals, as expected and its melting point range was 78.5-82 . The melting point range was within of the melting point of the desired product, which means that the product is pure.

4. Experiment #4 (even more catalyst)

9-hydroxyfluorene (0.1830 g) and H-K-OMS-2 catalyst (0.4074 g.) were added. The reaction was complete after 20 minutes. The progress of the reaction was checked every 5 minutes for completion. The solvent was of a yellow, a good indication. The recrystallized product was yellow crystals, and its melting point range was 81.5-84 . The recrystallized product weighted 0.0245 g. with a percent yield of 13.56%.

5. Experiment #5

9-hydroxyfluorene (0.1827 g) and H-K-OMS-2 catalyst (0.405 g.) were added. Reaction complete after 20 minutes. The product was yellow crystals, melting point 79.5-83.5 .

6. Experiment #6

9-hydroxyfluorene (0.1833 g) and H-K-OMS-2 catalyst (0.4022 g.) were added. The reaction was complete after 15 minutes. The product was yellow crystals, melting point 79-83 .

7. Experiment #7

9-hydroxyfluorene (0.1836 g) and H-K-OMS-2 catalyst (0.4048 g.) were added. Reaction complete after 20 minutes. The product was yellow crystals, melting point 81.5-84.3 .

8. Experiment #8

9-hydroxyfluorene (0.1834 g) and H-K-OMS-2 catalyst (0.4015 g.) were added. Reaction complete after 20 minutes. The product was yellow crystals, melting point 80.5-83.5 .

F. Oxidation using recycled H-K-OMS-2

1. Experiment #1

9-hydroxyfluorene (0.1822 g) and recycled H-K-OMS-2 catalyst (0.4033 g.) were added. The reaction was refluxed for about an hour and a half. The progress of the reaction was followed every ten minutes by TLC. It seems like the reaction never went to completion, this could be cause by the catalyst being completely doped from previous reactions.

G. Oxidation using 0.4 g of H-K-OMS-2 by Organic Chemistry Class

The organic chemistry class was able to run this experiment in order to see if, in fact, this lab could work as a lab period for future Organic Chemistry courses. The organic chemistry class ran seven reactions using the same procedures in all of them. The procedure that the class followed is shown in appendix 1.

H. Apparatus and Procedure

The synthesis of the catalyst as well as the oxidation of the alcohol had the same set up. The apparatus shown below (image 1) was set up so that two reactions could be running at the same time; by doing this we saved water as well as time. The round bottom flask was loaded with reactants in order for the reaction to proceed. In all the oxidation experiments, a 100 round bottom flask was use, and a 250 ml was use for the synthesis of the catalyst. Once the reactions were completed, the catalyst was dried and grounded to a powder by mortar in order to be

use. The oxidation reactions were analyzed by TLC, image 2 shows the TLC set up that was use to check the progress of the reaction as well as its completion. The silica plates were spotted with the starting material dissolve in toluene, the reaction, and the desire product dissolve in toluene. The reaction spot was compared to that of the starting material as well as the desire product. By doing this, we were able to analyze the reactions qualitatively and somewhat quantitatively. As mentioned before, the oxidizing reactions were cooled to room temperature, and then filtered before evaporating the solvent via rotary evaporator. Once we had our crude product, we recrystallized it and took its melting point using an electrothermal melting point apparatus (image 3). Taking the melting point is one of the most effective methods to check for the quality of the product. NMR was another option but we decided that taking the melting point took less time and a better method.

IV. Results

Since we could not find anything while using K-OMS-2 for our reactions, the results are based on the results that we have for the reactions with H-K-OMS-2 that were done by the Organic Chemistry class and me.

The results in table 1 were the ones that I recorded from my reactions. Notice that only seven of the eight reactions are on the table. The first experiment was not completed because the solvent dissolved after taking several samples from the solution, as I mentioned in the procedure segment for this particular experiment. From the results in table 1 and 2 we can see that after adding 0.4 grams of the H-K-OMS-2 catalyst, the reaction went to completion in an average of 20 minutes and with very good melting point ranges, by 80-83 being the melting point of 9-fluorenone. Most of the melting point ranges were within of our desire melting point range, which means that the final products were mostly pure.

By looking at the results there is a greater confidence in that the H-K-OMS-2 catalyst works well for the oxidation reaction that we wanted, 9-flurenol to 9-flurenone. From the data we are confident to state that the reaction can be carry to completion within 20 minutes, this is a decrease in time from one hour to 20 minutes, saving 40 minutes of time that we can use for the following procedures in the lab. Also, from the data we are confident that the product is pure and that future reactions can obtain this purity by following the procedures stated well. Lastly, this lab proves that it can be repeatable by having several Organic Chemistry students doing it, while following the procedures provided, and getting the results that were expected in every case.