## 3 Results and Discussion
### Synthesis of Methyl and Decyl Esters  
Following the optimization of the synthesis procedure, esters derived from fatty carboxylic acids coupled with MeOH and fatty alcohol 1-decanol were produced, as reported previously. After confirming an acceptable degree of purity (\(\geq\)89%), the thermal properties of the different esters were determined and subsequently analyzed and compared, in order to identify possible trends between chemical structure and thermal behavior, and to gain a broader overview of the melting points of different esters. Concerning ATR-IR characterization, the appearance of the ester characteristic peak at 1735 cm\({}^{-1}\), the progressive disappearance of the broad alcohol peak at 3100-3600 cm\({}^{-1}\), and of the acid at 1705 cm\({}^{-1}\) over time proved the efficiency of the reaction and the formation of the desired product. For all 1-decanol esters, however, a ratio of about 2:1 between the ester peak and the acid peak, respectively, was observed after drying with Rotavapor. This, together with the presence of a peak in the alcohol region, proved that not all reagents had been consumed during the reaction time. Therefore, crystallization in MeOH was performed until there was no visible residual alcohol peak and acid peak in the final spectra. Figure 9 shows the difference between unpurified decyl palmitate (DEPA) and DEPA crystallized twice in MeOH with a ratio of 1:10 for DEPA:MeOH. Generally, as reported previously, one or two crystallizations were sufficient to obtain degrees of purity over 89%. Figure 8: TGA graph of mass loss for MEPA produced in the laboratory. No significant differences with commercial MEPA were observed, as both samples registered a mass loss \(\leq\) 5% before 150 \({}^{\circ}\)C, and the remaining mass was lost in between the range 150 \({}^{\circ}\)C–240 \({}^{\circ}\)C as expected. A clear gain in the ester band was achieved, confirming the efficacy of the purification process. However, besides purity control and synthesis control, the IR could not confirm the true identity of the esters created since no clear differences were visible in terms of the ester peak and alkane chain peaks at 2920 and 2850 cm\({}^{-1}\). Therefore, the structure of the produced esters had to be recognized through NMR and GC-MS analysis. The mass spectra recorded for methyl esters showed the same peaks reported for MEPA, confirming the cleavage of a methyl group with peak at 239 \(m/z\). Esters derived from different fatty acids could be recognized by the longer or shorter fragmentation of the alkane chain by progressive loss of -CH\({}_{2}\) (14 \(m/z\)) and by the molecular ion. On the other hand, spectra for decyl esters showed a different fragmentation pattern, especially regarding the cleavage of the alcohol chain. For instance, for DEPA (molecular peak at 396 \(m/z\)), a strong signal was recorded due to the loss of the decyl alkane chain (loss of 141 \(m/z\), peak at 255 \(m/z\)), thus forming a carboxylate group. The decyl aliphatic chain is then thought to form a decene through resonance to give the observed mass loss of 139 \(m/z\) at corresponding peak 257 \(m/z\). The alcohol cleavage with loss of 1-decanol (loss of 157 \(m/z\)) was observed at 239 \(m/z\), which confirms that the ester analysed was indeed a decyl ester. Additionally, the usual progressive fragmentation of the alkyl chain from the acid side is observed through steps of 14 \(m/z\) loss each. Similarly, the structures of the different esters could be easily identified through \({}^{1}\)H NMR analysis, as well as detection and quantification of impurities from residual alcohol or acid (Figure 10). All the \({}^{1}\)H NMR spectra of methyl esters showed a high degree of purity and no residual alcohol, therefore their purity was estimated at \(\geq\)98%.