## 2 Materials and Methods
### Gas-Phase Standard Molar Enthalpies of Formation of Alkyl-Quinolines and Alkyl-Pyridines  
The standard molar enthalpies of formation, \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\), are an essential part of thermodynamic information that is required to optimize of the heat management in chemical technology. The available for quinolines enthalpies of formation in the condensed phase, \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\) (cr or liq), are collected and averaged in Table 9, column 2. These data were used together with the vaporization enthalpies of quinolines, which evaluated and averaged in this work (see Table 2) to derive the experimental gas-phase standard molar enthalpies of formation, \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}(\text{g})_{\text{exp}}\) at 298.15 K (see Table 9, column 4). In the last decade we systematically used the high-level quantum-chemical calculations for the mutual validation of \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}(\text{g},298.15\text{ K})\)-values obtained from the experimental and computational thermochemistry. The recent development of the high-level composite methods has led to computation of the gas-phase enthalpies of formation with a \"chemical accuracy\" that is commonly defined as \(\pm 4\)-\(5\) kJ.mol\({}^{-1}\)[52; 53; 54]. An agreement or disagreement between the _theoretical_ and _experimental_\(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}(\text{g},298.15\text{ K})\)-values serves as an indicator of the consistency and reliability for both results, the prerequisite for the use of thermochemical data in chemical technology. We used the experimental \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\) (g, 298.15 K)-values from Table 9 together with the evaluated experimental gas-phase enthalpies of formation of alkyl-pyridines [55] to validate the high-level quantum-chemical method G4 for the reliable calculation of the alkyl-substituted pyridines and quinolines. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Compound** & \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\) (liq or cr) & \(\Delta_{\text{l},\text{cr}}^{8}H_{\text{m}}^{\text{o}}\) **b** & \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\) **(g)** **exp** & \(\Delta_{\text{f}}H_{\text{m}}^{\text{o}}\) **(g)** **theor** **c** \\ \hline
1 & 2 & 3 & 4 & 5 \\ \hline quinoline (liq) & 141.2 \(\pm\) 0.9 [14] & 59.3 \(\pm\) 0.4 & 200.5 \(\pm\) 1.0 & 198.1 \\ \hline
2-methylquinoline (liq) & 93.0 \(\pm\) 2.5 [17] & & & \\  & 95.2 \(\pm\) 0.9 [18] & & & \\  & **94.9 \(\pm\) 0.8**d  & **61.7 \(\pm\) 0.3** & **156.6 \(\pm\) 0.9** & 155.6 \\ \hline
4-methylquinoline (liq) & 94.5 \(\pm\) 2.6 [17] & 64.1 \(\pm\) 0.4 & 158.6 \(\pm\) 2.7 & 161.3 \\ \hline
6-methylquinoline (liq) & 93.3 \(\pm\) 2.4 [17] & 64.0 \(\pm\) 0.3 [17] & 157.3 \(\pm\) 2.4 & 163.3 \\ \hline
8-methylquinoline (liq) & 102.0 \(\pm\) 2.4 [17] & & & \\  & 103.2 \(\pm\) 1.6 [18] & & & \\  & **102.8 \(\pm\) 1.3**d  & **62.0 \(\pm\) 0.3** [18] & **164.8 \(\pm\) 1.3** & 161.4 \\ \hline
2,6-dimethylquinoline (cr) & 36.4 \(\pm\) 2.5 [51] & & & \\  & 36.2 \(\pm\) 0.9 [34] & & & \\  & **36.2 \(\pm\) 0.8**d  & **85.1 \(\pm\) 0.4**  & **121.3 \(\pm\) 0.9** & 121.3 \\ \hline
2,7-dimethylquinoline (cr) & 34.3 \(\pm\) 2.6 [51] & 85.5 \(\pm\) 1.6 [51] & 119.8 \(\pm\) 3.1 & 120.6 \\ \hline
2-phenylquinoline (cr) & 181.8 \(\pm\) 3.9 [20] & 104.8 \(\pm\) 2.2 & 286.6 \(\pm\) 4.5 & - \\ \hline \hline \end{tabular}  
* The uncertainties are given as twice the standard deviation. Values given in bold are recommended for thermochemical calculations.[ENDFOOTNOTE]
* Evaluated experimental values from Table 2. \(\ddagger\) Theoretical value calculated using the G4 method (see Table 10). \(\ddagger\) Weighted average from data given in this table (experimental uncertainties used as the weighing factor).[ENDFOOTNOTE]
* The uncertainties are given as twice the standard deviation. Values given in bold are recommended for thermochemical calculations.[ENDFOOTNOTE]
* Weighted average from data given in this table (experimental uncertainties used as the weighing factor).[ENDFOOTNOTE]  
\end{table}