Figure 1: Main reaction of maleic anhydride to maleic acid to fumuric acid The purpose of this experiment is to demonstrate how maleic anhydride so most stable in the trans isomer as reached by two transformations. The cis alkene is transformed to its trans isomer by protonating the π bond. This broken π bond, frees up the σ bond and is free to rotate to the most stable conformation is reached in the main reaction shown in figure 1. The mechanism of the reaction is shown below in two steps (figures 2 and 3). The first transformation is the hydrolysis of maleic anhydride and the second one is the rotation of the cis double bond to the trans double bond found in fumaric acid. Isomerization is a chemical reaction, where the primary product is isomeric with the main reactanct, meaning the same molecular formula but different chemical structure.1 Maleic anhydride, maleic acide, and fumaric acid are multifunctional chemical intermediates.2 Maleic acid and fumaric acid have physical properties that differ due to the cis and trans configurations about the double bond.
Figure 2: Step 1 is the hydrolysis of maleic anhydride to maleic acid
Figure 3: Step 2 is the isomerization of maleic acid to fumuric acid
Table of Reagents:
Molecular Weight (g/mol)
Amount Used (ml/g/mol)
Melting Point/ Boiling Point (°C)
Maleic Anhydride C4H2O3
Maleic Acid C4H4O4
Table 1: Table of Reagents
One gram of maleic anhydride was dissolved in 10 ml of 24% hydrochloric acid in an Erlenmyer flask. The flask was placed in a boiling water bath in order to dissolve the acid. The mixture was cooled in an ice water bath and then the precipitate...
References: Felthouse, T. R., Burnett, J. C., Horrell, B., Mummey, M. J., & Kuo, Y.-J. (2011, April 26). Maleic Anhydride, Maleic
Acid, and Fumaric Acid. Retrieved November 16, 2011, from Huntsman Petrochemical Corporation: http://www.usouthal.edu/chemistry/barletta/felthouse.pdf
Isomerization. (2011, October 11). Retrieved November 16, 2011, from IUPAC Gold Book:
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