<![CDATA[Background: Fumaric acid (trans-butenedioic acid) is the thermodynamically stable geometric isomer of maleic acid (cis-butenedioic acid). It serves as the parent compound of dimethyl fumarate (DMF), an FDA-approved immunomodulatory agent used for relapsing-remitting multiple sclerosis and moderate-to-severe plaque psoriasis. Laboratory-scale synthesis of fumaric acid from maleic acid via acid-catalyzed isomerization provides a practical route for studying the physicochemical properties of this compound. Objective: This study aimed to synthesize fumaric acid through hydrochloric acid (HCl)-catalyzed isomerization of maleic acid under reflux conditions and to characterize the products by melting point determination and gravimetric yield analysis. Methods: Maleic anhydride (2 g) was hydrated in boiling distilled water (5 mL) to produce maleic acid, which was crystallized by cooling. The filtrate containing dissolved maleic acid was treated with concentrated HCl (2 mL) and refluxed for 15 minutes. Fumaric acid was isolated by ice-bath crystallization and gravity filtration. Both products were characterized by gravimetric yield and melting point analysis. Results: Maleic acid was obtained with a yield of 25.39% (0.6011 g) and a melting point of 139°C, consistent with the literature range (130-139°C). Fumaric acid was obtained with a yield of 34.64% (0.6119 g) and a melting point of 280°C, slightly below the reported literature range (286-302°C), suggesting the presence of minor impurities. Conclusion: The HCl-catalyzed reflux method converted maleic acid to fumaric acid through an addition-rotation-elimination mechanism. The higher melting point of fumaric acid reflects its greater molecular symmetry and stronger intermolecular interactions in the crystal lattice.]]>
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