###### Abstract  
Group Contribution (GC) methods to predict thermochemical properties are eminently important in chemical process design. Following our earlier work in which a Group Contribution (GC) model was presented to account for the gas-phase heat of formation of organic molecules which, for the first time, revealed chemical accuracy (1 kcal/mol or 4 kJ/mol), we here present Group Contribution parameters for a range of additional series of molecules allowing the application to a wider range of molecules whilst, mostly, retaining chemical accuracy. The new classes of molecules include amines, alkylesters, and various substituted benzenes, including t-butyl-benzenes, phenols, methoxybenzenes, anilines, benzaldehydes, and acetophenones, and finally furrans and indoles/indiines. As in our previous works on this theme, again the critical selection of experimental data was crucial. Not meeting the criterion for chemical accuracy occurred when steric interactions such as nearest neighbour substituents on a benzene ring were present, something which does not fit with the characteristics of the Group Contribution method. We also report some cases for which the experimental value does not seem correct, but where both the G4 and GC model values agree well. In general, in line with accounts in the literature, the G4 method performs really well. Contrary to other related works, we have applied conformational averaging to obtain a slightly more realistic G4 result. Although the difference is generally only a few kJ/mol, this may still be relevant when attempting the development of a model with chemical accuracy, e.g., 4.2 kJ/mol. e +
Footnote †: journal: Chemical accuracy  
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important and widely applied methods [1; 2; 3; 4; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15]. The original GC method is based on the assumption that a molecule can be decomposed into molecular fragments which are in essence mutually independent, and the molecular property of interest is the sum of the individual properties of the molecular fragments. The GC method is a so-called data-driven model with experimental data being used to parametrize the model; for the heat of formation \(\Delta\)H\({}_{\text{f}}\) the essential equation reads  
\[ \begin{array}{c}\Delta\text{H}_{\text{f}}=\sum\text{Nj}.\Delta\text{H}_{ \text{f}}(\text{j})\\ \text{j}=1,\text{N}\end{array}  \tag{1}\]  
In Equation (1), Nj represents the number of times Group j occurs in the molecule of interest, whereas \(\Delta\)H\({}_{\text{f}}\)(j) is the Group Contribution of the chemical Group j to the heat of formation. In this work, the \(\Delta\)H\({}_{\text{f}}\) (in this paper, also indicated as dHf) is the enthalpy of formation for the ideal gas species at the reference temperature of 298.15 K.  
In the four earlier papers, the Group Contribution (GC) method was reevaluated and, despite the method being old, a substantial and necessary increase in performance was still achieved [1; 2; 3; 4]. It was demonstrated that it is possible to establish a GC parametrization for organic molecules achieving unprecedented chemical accuracy.