In essence, the reaction reduces the system's entropy as it progresses, favoring arrangements with lower degrees of freedom or fewer microstates. The Gibbs free energy equation, ΔG = ΔH -TΔS, highlights how ΔS influences reaction spontaneity, particularly at higher temperatures where the -TΔS term becomes significant. For gas-phase reactions, ΔS captures molecular ordering effects, with larger alkanes typically exhibiting lower ΔS values due to increased organization in the transition to products. Figure displays the entropy change (ΔS) for the combustion of alkanes (C₁ to C₁₀) as a function of the number of carbon atoms (n) using various DFT methods and split-valence basis set. The results show a general decrease in entropy change with increasing chain length, indicating that longer alkanes contribute to larger reductions in entropy during combustion. The entropy change during the combustion of alkanes becomes increasingly negative as the number of carbon atoms in the alkane rises. This trend is attributed to the larger, more complex molecular structures of higher alkanes, which possess greater vibrational, rotational, and translational degrees of freedom compared to smaller alkanes . During combustion, these degrees of freedom are lost as the alkanes are broken down into simpler molecules like CO₂ and H₂O, which have fewer available microstates per molecule. Consequently, the overall entropy decreases more significantly for larger alkanes. Additionally, higher alkanes produce a greater number of smaller, more ordered molecules during combustion, further amplifying the decrease in entropy. This combined effect of reduced molecular complexity and increased order in the products leads to a more pronounced entropy reduction for larger alkanes. Interestingly, the magnitude of this entropy change shows subtle variations across computational methods. For example, LSDA predicts the most stable states, while other DFT methods yield comparable results with slight differences. However, Figure highlights that when ΔS is calculated using correlation-corrected basis sets, the trend across the number of carbon atoms in alkanes remains consistent, but the behavior of the DFT functionals diverges. Double-hybrid and dispersion-corrected functionals align closely with LSDA, producing the least random arrangement of combustion products. In contrast, GGA, meta-GGA, and hybrid functionals suggest less favorable conditions for combustion reactions. Overall, the analysis of reaction enthalpy, change in Gibs free energy, and change in entropy for alkane combustion reaction underscores the importance of selecting a DFT method for computational analysis with appropriate set of functionals and basis sets for accurate predictions. In cases where experimental thermodynamic data is unavailable, careful selection of computational approaches can act as a reliable tool. All the numerical data for thermodynamic properties can be found in Table to Table in the Supplementary data file.