Asymmetric Epoxidation of Dihydronaphthalene with a Synthesized Jacobsen's Catalyst
Synthesis of (R, R) Jacobsen's Catalyst (Scheme 1). The first step in the synthesis of Jacobsen's catalyst was the selective crystallization of one of three stereoisomers present in 1,2-diaminocyclohexane. The yield from this reaction was 8.9% (Appendix 1). The reaction produced 1.2015 g of an off-white crystal (Product 1) with a melting point of 270.4-273.8 °C, which was identified as (R, R)-1,2-diaminocyclohexane mono-(+)-tartrate salt (Table 1).
Table 1. Selected Data Utilized in Identification of Product 1
Compound Product 1 (R, R)-1,2-diaminocyclohexane mono-(+)-tartrate saltIII
Physical Description Off-white crystals Off-white to beige crystalline solid
Melting Point (°C) 270.4-273.8 273
The percent yield was so low (8.9%) largely because of experimental error. An unknown amount of Product 1 was lost because it was not retrievable from the reaction flask, and a further unspecified amount was lost when a portion of the product recrystallized on the filter
paper during a vacuum filtration. This recrystallization occurred because the funnel and filter flask were not heated properly. The second step of the Jacobsen synthesis involved the reaction of the isolated diamine salt (Product 1, (R, R)-1,2-diaminocyclohexane mono-(+)-tartrate salt) with an aldehyde (3,5-di-tert-butylsalicylaldehyde) to produce the organic backbone of the catalyst. The percent yield from this reaction was 77%. This reaction produced 1.56 g of an oily, yellow powder (Product 2) with a melting point of 202.9-205.4 °C and an optical rotation ([a]D20) of -314° that was identified as (R, R)-N, N'-Bis (3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine (Table 2).
Table 2. Selected Data Used in Identification of Product 2
Compound Product 2 (R, R)-N, N'-Bis (3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamineIII
Oily, yellow powder Yellow powder
Melting Point (°C)
[a]D20 -314° -315°
Product was lost during transfers between containers and in the separatory funnel when the reaction material was washed. It is also possible that product was lost because the reaction was not allowed to reflux to completion and was cut short by fifteen minutes. The fourth and final step of the Jacobsen catalyst synthesis involved the insertion of the oxidizing metal (in the form of Mn(OAc)2*4 H2O followed by 2 equivalents of LiCl) into the organic backbone (Product 2) of the catalyst. The percent yield for this reaction was 19%. The reaction produced 0.22 g of a brown, oily solid (Product 3) with a melting point of 331-333.6 °C that was identified as Jacobsen's catalyst; [(R, R)-N, N'-Bis (3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminato (2-)]-manganese (III) Chloride (Table 3).
Table 3. Selected Data Used in Identification of Product 3
Compound Product 3 Jacobsen's Catalyst
Physical Description Brown, oily solid
Melting Point (°C) 331.4-333.6 324-326
Again, product was lost because the reflux was cut short and not allowed to run to completion, causing loss of product. Additional product was either lost or unreacted when the air bleed tube was inserted, causing some product to splash out of the reaction flask. These experimental errors may very well have led to a high amount of impurities in Product 3, which would account for the difference between the experimental melting point and the
literature value. The net percent yield for the synthesis of Jacobsen's catalyst was 1.9% (Appendix 1)
Asymmetric Epoxidation of Dihydronaphthalene. The synthesized Jacobsen's catalyst (Product 3) was used to run an enantiomerically guided epoxidation of an unfunctionalized alkene (dihydronaphthalene). The percent yield for this reaction was 71%. The reaction yielded a 0.4 g of a dark brown, oily solid (Product 4) that was purified by flash chromatography, analyzed by GC/MS and IR (NEAT) (Figure 1, Table 4).
Table 4. Selected IR Data for Identification of Epoxidaton of Dihydronaphthalene Products
Compound Product 4***Fig 1,2-epoxydihydronaphthalene Naphthalene
Prominent IR Peaks 2964.0 (C-H, alkane)
1747.0 (C=C, alkene)
1239.0 (C-O, ether)
1048.7 (C=C-H, alkene)
2970-2850 (C-H, alkane)
1750-1620 (C=C, alkene)
1300-1000 (C-O, ether)
1050-675 (C=C-H, alkene) 2970-2850 (C-H, alkane)
1750-1620 (C=C, alkene)
1050-675 (C=C-H, alkene)
Retention Times (min.) and Corresponding Mass Spec (m/z) 3.75 min.: (128)
6.75 min.: (146)
Structure, Physical Properties
Product 4 displays properties of both 1,2-epoxydihydronaphthalene and naphthalene. The peaks seen in the IR (NEAT) of product 4 at 2964.0, 1747, 1239, and 1048.7 cm-1 (FIG 1) could be interpreted to represent the presence of just 1,2-epoxydihydronaphthalene. The GC that was run on product 4; however, indicated that naphthalene was also present (FIG 2-4). This leads to the conclusion final product of this Jacobsen catalyzed epoxidation was a mixture of 1,2-epoxydihydronaphthalene (30%) and naphthalene (70%) (FIG 2-3, Scheme 2). The presence of an oxidized product (naphthalene) indicates that the solution in which the reaction took place was probably too basic. Such a situation could be corrected by either adding less Clorox or by adding NaOH that is less concentrated than 1M. It is also possible that not all of the epoxidized product was isolated, and that much of it remained stuck in the silica gel of the flash chromatography column. In order to remedy this situation, a solvent that is more polar than the 25% ethyl acetate in hexane that was used for the flash chromatography in this experiment.
The synthesized Jacobsen's catalyst did not guide this enantiomeric epoxidation as was hoped; however, both the reagent and mechanism showed that it is possible to produce a significant amount of an enantiomerically enriched epoxide. The problem with the reaction described above was not the reagent or the mechanism of the reaction, it was the conditions in which the reaction was carried out. In order for the Jacobsen catalyzed epoxidation to produce highly enamtiomerically enriched epoxides as was hoped, more care must be taken in the transferring and washing of products, and reactions must be allowed to run to completion. If this is successfully done, then the impurities that were present in the final product will be effectively minimized, and the results that were obtained by Dr. E. N. Jacobsen may be repeated.
Pages: 1 2
Please do not pass this sample essay as your own, otherwise you will be accused of plagiarism. Our writers can write any custom essay for you!
Asymmetric Epoxidation Of Dihydronaphthalene With A Synthesized Jacobs Sample essay topic, essay writing: Asymmetric Epoxidation Of Dihydronaphthalene With A Synthesized Jacobs - 1018 words
.. pH 11.3 by adding 1M NaOH (1 drop). [(R, R)-N, N'-Bis(3,5-di-tert-butylsalicylidene)-1,2 -cyclohexanediaminato (2-)]-manganese (III) chloride(0.2 g, 0.00031 mol) was added to a solution of 4-phenylpyridine N-oxide (0.13g, 0.00076 mol) and dihydronaphthalene (0.51 g, 0.0038 mol) in CH2Cl2 (5 mL,0.076 Relative Reactivity Of Anilines Sample essay topic, essay writing: Relative Reactivity Of Anilines - 498 words
Relative Reactivity of AnilinesAbstract: Various Anilines were tested with Br2/HBr solution, the products were crystallized and melting points attained to verify relative reactivity. My assignment, 2,4-Dibromoanisol, was prepared in a yield of 52% with a melting point of 55-58 C. Reaction:Mechanism:Procedure: Anisole (0.35mL, 0.0378mol) Effect Of Temperature On Raction Rate Sample essay topic, essay writing: Effect Of Temperature On Raction Rate - 495 words
Effect of temperature on RXN rateDaniel Amireh10-3Khalil KarajehFactors affecting rate of reaction:Surface area - as we increase surface area, we increase the reaction rate. The more the collisions the faster the reaction. Concentration - as we increase concentration we increase the reaction 2001 Noble Prize Winners in Chemistry Two Americans and a Japanese were awarded this year's Nobel Prize in Chemistry for developing more efficient chemical reactions to produce many medicines, including L-dopa, the standard treatment for Parkinson's disease. Dr. William S. Knowles, 84, of St. Louis, who retired from the Monsanto Company in 1986, and Dr. Ryoji Noyori, 63, director of the Oxidation With Sodium Hypochlorite Sample essay topic, essay writing: Oxidation With Sodium Hypochlorite - 956 words
Final weight percent yield 2,4-DNP Tollen's test pathway.42g 67% positive negative oxidation of secondary OHGood Things My experiment went well. I began my experiment with.64g of 2-ethyl-1,3-hexanediol. The molecular weight of this compound is 146.2g/mol. It is converted into 2-ethyl-1-hydroxyhexan-3-one. This compounds molecular weight