## 3 Results
### Alkyl Esters
& **MG** & **CG** & **JR** \\ \hline acetic acid methyl ester & \(-411.9\) & \(-410.7\) & \(1.2\) & \(1.2\) & \(-411.6\) & \(-411.6\) & \(0.9\) & \(-411.8\) & \(-424.9\) & \(-422.5\) \\ \hline
**pentanoic acid methyl ester** & \(-471.2\) & \(-472.6\) & \(-1.4\) & \(1.4\) & \(-475.1\) & \(-472.6\) & \(0.0\) & \(-484.5\) & \(-481.8\) & \(-484.5\) \\ \hline hexanoic acid methyl ester & \(-492.6\) & \(-493.2\) & \(-0.6\) & \(0.6\) & \(-496.4\) & \(-493.4\) & \(0.2\) & \(-505.2\) & \(-502.6\) & \(-505.1\) \\ \hline heptanoic acid methyl ester & \(-515.9\) & \(-513.9\) & \(2.0\) & \(2.0\) & \(-517.8\) & \(-514.3\) & \(0.4\) & \(-525.9\) & \(-523.4\) & \(-525.7\) \\ \hline octanoic acid methyl ester & \(-533.8\) & \(-534.5\) & \(-0.7\) & \(0.7\) & \(-539.2\) & \(-535.2\) & \(0.7\) & \(-559.9\) & \(-544.1\) & \(-546.4\) \\ \hline nonanoic acid methyl ester & \(-553.9\) & \(-555.1\) & \(-1.2\) & \(1.2\) & \(-560.5\) & \(-555.0\) & \(-0.1\) & \(-569.9\) & \(-564.9\) & \(-567.0\) \\ \hline decanoic acid methyl ester & \(-573.8\) & \(-575.8\) & \(-2.0\) & \(2.0\) & \(-581.8\) & \(-576.3\) & \(0.5\) & \(-577.2\) & \(-588.7\) & \(-587.7\) \\ \hline tridecanoic acid methyl ester & \(-635.4\) & \(-637.7\) & \(-2.3\) & \(2.3\) & \(-645.7\) & \(-639.2\) & \(1.6\) & \(-639.3\) & \(-648.0\) & \(-649.6\) \\ \hline pentadecanoic acid methyl ester & \(-680.0\) & \(-678.9\) & \(1.1\) & \(1.1\) & \(-688.4\) & \(-680.6\) & \(1.7\) & \(-680.7\) & \(-687.5\) & \(-690.9\) \\ \hline ethylacetate & \(-444.1\) & \(-444.4\) & \(-0.3\) & \(0.3\) & \(-444.4\) & \(-444.4\) & \(0.0\) & \(-432.5\) & \(-445.6\) & \(-443.2\) \\ \hline propionic acid, ethyl ester & \(-463.6\) & \(-465.0\) & \(-1.4\) & \(1.4\) & \(-465.9\) & \(-465.9\) & \(0.9\) & \(-453.1\) & \(-461.1\) & \(-463.8\) \\ \hline butylacetate (acetic acid butyl ester) & \(-485.6\) & \(-485.6\) & \(0.0\) & \(0.0\) & \(-485.3\) & \(-483.3\) & \(-2.3\) & \(-473.9\) & \(-487.1\) & \(-484.5\) \\ \hline
**pentanoic acid ethyl ester** & \(-506.9\) & \(-506.2\) & \(0.7\) & \(0.7\) & \(-507.9\) & \(-505.4\) & \(-0.8\) & \(-505.2\) & \(-502.6\) & \(-505.1\) \\ \hline pentanoic acid butyl ester & \(-533.6\) & \(-526.9\) & \(6.7\) & \(6.7\) & \(-528.0\) & \(-525.0\) & \(-1.9\) & \(-525.8\) & \(-523.4\) & \(-525.7\) \\ \hline pentanoic acid butyl ester & \(-560.2\) & \(-547.5\) & \(12.7\) & \(12.7\) & \(-548.9\) & \(-544.4\) & \(-3.1\) & \(-559.9\) & \(-544.1\) & \(-546.4\) \\ \hline isopropyl acetate (acetic acid 1-methyl ester) & \(-481.7\) & \(-472.2\) & \(9.5\) & \(9.5\) & \(-482.2\) & \(-481.7\) & \(9.5\) & \(-477.5\) & \(-483.2\) & \(-469.1\) \\ \hline pentanoic acid isopropyl ester & \(-544.9\) & \(-534.1\) & \(10.8\) & \(10.8\) & \(-546.1\) & \(-543.1\) & \(9.0\) & \(-536.2\) & \(-552.4\) & \(-531.0\) \\ \hline
2-**methylbutanoic acid** & \(-492.5\) & \(-477.7\) & \(14.8\) & \(14.8\) & \(-477.8\) & \(-477.8\) & \(0.1\) & \(-484.2\) & \(-465.1\) & \(-489.7\) \\ \hline
**3-methylbutanoic acid methylester** & \(-497.9\) & \(-479.8\) & \(18.1\) & \(18.1\) & \(-483.7\) & \(-483.7\)are only having a different number of aliphatic CH\({}_{2}\) groups and therefore one should expect very regular behaviour. The difference in dHf between nonanoic acid methyl ester and decanoic acid methyl ester according to the Marrero-Gani method reads 7.3 kJ/mol only, whereas the addition of a single CH\({}_{2}\) group in the alkyl chain should lead to a difference of approximately 20 kJ/mol. For acetic acid methyl ester, the Marrero-Gani value is spot on, but for many others, including pentanoic acid methyl ester, hexanoic acid methyl ester, and nonanoic acid methyl ester, the difference with the experimental value is more than 10 kJ/mol. A more detailed analysis reveals the origin of these observations.