Abstract
In this experiment, 5 mL of toluene solution was transferred in a 25 mL round bottom flask and then 0.40 g maleic anhydride and 0.4 g E, E-2, 4-hexadien-1-l added. Ethyl acetate was used as a solvent to carry out a TLC analysis on the mixture produced after reaction completion mainly to determine the presence of any starting material in the mixture. The reaction mixture was then slowly cooled to room temperature. There was crystallization taking place as the reaction cooled, white crystals were formed.
The mixture was further cooled in for 10 minutes in a water bath to promote crystallization to completion. The product formed was then separated by use of vacuum filtration. The product obtained was then cleaned by using cold toluene after which it was dried in an air stream. The sample product was then re-crystallized to obtain a product that was analytically pure. An H-NMR was taken using a JOEL ecx 400MHz proton NMR
Introduction
The aim of this experiment was to perform a Diels-Alder reaction of maleic anhydride and toluene to yield cis-1, 3, 3a, 4, 5, 7a-hexahydro-5-methyl-3-oxo-4-isobenzofuran-caroxylic acid. The Diels-Alder reaction was named after Otto Diels and Kurt Alder, both great German scientists. These two scientists did extensive study of the reactions that produced cycloadducts from dienophiles and 1, 3-dienes. As a result of their endeavors, they were rewarded with a Nobel Prize in Chemistry in the year 1950. The Diels-Alder reaction is generally a cyclization reaction involving an alkene and a diene as the main reactants.
The product of this reaction is a 6-carbon compound. Generally, the three double bonds present in the reactant compounds are converted by breaking them into two single bonds and another double bond. The reaction system has proved to be highly useful as it doesn’t consume a lot of energy.
Reaction
In the above reaction mechanism, reactant 1(2, 4-hexadien-1-ol) undergoes cyclization with reactant 2 (maleic anhydride) in the presence of toluene. The reaction initially yields the intermediate product 3. This intermediate product goes through an intramolecular reaction which subsequently yields product 4 (cis-1, 3, 3a, 4, 5, 7a-hexahydro-5-methyl-3-oxo-4-isobenzofurancarboxylic acid)
General procedure
5mL of toluene was placed in a 25mL round bottom flask with a boiling stone. Then 0.40g (4.089mmol) of Maleic anhydride and 0.40g (4.218mmol) of E, E-2, 4-hexadien-1-ol were subsequently added. The reaction was heated and refluxed for 5 minutes, while preparing a Thin Line Chromatography plate. The reaction mixture was then checked to see if any starting materials were still present.
When the starting materials were no longer present, the reaction was then cooled to room temperature. White crystals should form on the sides of the round bottom flask. The reaction was then placed in an ice bath for complete crystallization. The crystals were then separated using a vacuum filtration and cleaned by washing with cold toluene. The sample was weighted and the yield was determined.
Experimental section
5ml of toluene was added to a 25ml round bottom flask with a boiling stone. Then 0.401g (4.089mmol) of maleic anhydride and 0.414g (4.218mmol) of 2, 4-hexadien-1-ol were added to the round bottom flask. The reaction mixture was then heated and refluxed for 6 minutes. A Thin Line Chromatography plate was prepared to see if the starting materials were still present. After the TLC plate showed that the starting materials were finished; the flask was allowed to cool to room temperature. Crystals were observed forming as the reaction mixture was cooling. The reaction flask was placed in an ice bath to finish crystallization.
The crystals and solution were separated by use of a vacuum filtration system and the crystalline product washed severally with cold toluene. The product obtained was weighed and found to be 0.436g (1.328mmol) of cic-1, 3, 3a, 4, 5, 7a-hexahydro-5-methyl-3-oxo-4-isobenzofuran-carboxylic acid; Giving a yield of 54.34%.
1.13(d, J=7.33Hz, 3H), 2.05(s, residual acetone), 2.67(m, 1H), 3.10(t, J=5.50Hz, 1H), 3.29(m, 1H), 3.43(q, J=4.58Hz, 1H), 4.10(q, J=3.21Hz, J=8.70Hz, 2H), 4.42(t, J=7.33Hz, J=8.70Hz, 1H), 5.62.
Results and discussion
The Diels-Alder reaction of maleic anhydride and 2, 4-hexadien-1-ol in the presence toluene in which the toluene was refluxed for 6 minutes did generate white crystalline product as it was being cooled to room temperature. The crystalline product was isolated by use of vacuum filtration apparatus and the yield obtained was 54.34%. An H- nuclear magnetic resonance of the final product did indicate the absence of any anhydride moiety, but it revealed the presence of two other products alongside the expected compound. This implies that there were other side reactions taking place in the reaction flask as well as the main intended reaction.
Through the H-NMR analysis it was concluded that the major product of the Diels-alder reaction was cic-1, 3, 3a, 4, 5, 7a-hexahydro-5-methyl-3-oxo-4-isobenzofuran-carboxylic acid. The H-NMR spectrum of the product did not indicate any overlapping resonances.
The outcome, stereo-chemically, of this experiment was expounded by use of the Endo rule.
Conclusion
In conclusion, the results obtained from the calculation of the yield of the product and the H-NMR spectrum analysis indicate that cic-1, 3, 3a, 4, 5, 7a-hexahydro-5-methyl-3-oxo-4-isobenzofuran-carboxylic acid was synthesized by the Diels-Alder reaction and the resonance peaks of the nuclear magnetic resonance correspond also to two other by-products. Therefore, the low percent yield obtained was due to the presence of side reactions the resulted in formation of two by-products.
Works Cited
R.K. Hill & J. Barbaro, “Experiments in Organic Chemistry” 2nd ed. (2000)
Ann. 1929, “Synthesis of the hydro aromatic sequence”, 470, 62
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