Counterion Effects in the Nucleophilic Substitution Reaction of the Acetate Ion with Alkyl Bromides in the Synthesis of Esters
Elizabeth M. Valentín and Ingrid Montes
Department of Chemistry, University of Puerto Rico-Río Piedras Campus, San Juan, Puerto Rico 00931
Waldemar Adam
Institute of Organic Chemistry, University of Würzburg, Am Hubland, D-97094 Würzburg, Germany; and Department of Chemistry, University of Puerto Rico-Río Piedras Campus, San Juan, Puerto Rico 00931
Esters are often employed as artificial flavorings in foods and drinks, since the more volatile ones possess distinctive odors characteristic of common fruits. The present laboratory experiment introduces students to the esterification method in which a nucleophilic substitution reaction (either SN2 or SN1) between an alkyl halide and metal carboxylate is employed. The students learn that the metal counterion plays an important role with regard to the efficiency of the reaction and that the ester yield depends on the type of mechanism, namely, whether an SN2 or SN1 process occurs. For this purpose, a simple ester is synthesized, its yield determined gravimetrically, its purity established by gas chromatography analysis, and its identity assessed by mass spectrometry. The results are explained in terms of Pearson's hard and soft acid–base principle (HSAB), an empirical concept rarely covered in introductory organic chemistry.
Valentín, Elizabeth M.; Montes, Ingrid; Adam, Waldemar. J. Chem. Educ.2009, 86, 1315.
Keywords
Acids / Bases; Esters; Gas Chromatography; Hands-On Learning / Manipulatives; Inquiry-Based / Discovery Learning; Laboratory Instruction; Mass Spectrometry; Mechanisms of Reactions; Nucleophilic Substitution; Organic Chemistry; Second-Year Undergraduate; Synthesis; Upper-Division Undergraduate
History
Created:
Last Updated:
9/16/2009
9/25/2009
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