Methyl Trans-Cinnamate Lab Report

Abstract – Methyl trans-cinnamate is an ester that contributes to the aroma of strawberry. It can be synthesized by an acid-catalyzed Fischer esterification of a methanol and trans-cinnamic acid under reflux. The solution was extracted to obtain the organic product, and evaporated residual solvent The yield was 68%, but there is some conflicting data regarding the purity. The melting point, IR, GC-MS indicate a highly pure desired product whereas 1H NMR shows there are unreacted reagents still present.

Introduction:
The purpose of this experiment is to synthesize the component of strawberry fragrance – methyl trans-cinnamate. This reaction is accomplished by a Fischer esterification of methanol and trans-cinnamic acid refluxed for 1 hour

The literature melting point range of methyl trans-cinnamate is ~34-38oC (Aldrich).4 The obtained melting point of the crude was 34.5-35.5oC, which is a highly narrow range of less than 1oC difference and it also falls within the expected melting point range. Hence, the crystal lattice structure of the product is largely intact, requiring an even amount of thermal energy to melt the sample. The experimental melting point range indicates the crude product is relatively pure with minimal impurities. The percent yield was satisfactory, having a 68% yield. To optimize this yield, consider the steps in how the reagents are introduced to the reaction mixture in terms. It is understood the mechanism is acid-catalyzed where protons coordinate with the carbonyl oxygen to make the carbonyl carbon more electropositive for nucleophilic attack (Scheme 1). In the experimental procedure all reactants were added together, this is inefficient as the protons can coordinate with either trans-cinnamic acid or methanol. Coordination with methanol is unnecessary as it reduces its nucleophilicity and makes less protons available to coordinate with the carboxylic acid. To improve

This supports the isolated product is majority made of the desired product and is largely pure. Mass spectrometry of the crude product shows the molecular ion peak is 162.1, which is the largest fragment in the mass spectrum (Figure 4) and corresponds to the molecular weight of methyl trans-cinnamate (Table 1). The base peak is 131, inferring the fragment lost is 31 m/z in size. This 31 m/z matches the OCH3 fragment of the ester, and would not result from a trans-cinnamic acid. This is evidence the product was successfully