Group increment calculation

Calculation of group increments for oxygen, sulfur and nitrogen compounds has allowed the estimation of conventional ring-strain energies (CRSE) for saturated heterocycles from enthalpies of formation. For 1,3-dioxolane, CRSE is about 20 kJ mol . In 2,4-dialkyl-l,3-dioxolanes the cis form is always thermodynamically the more stable by approximately 1 kJ mol" . 

The volume and surface of 3-8 were calculated, and were found to agree with those obtained from sums over group increments within 1%. Thus, it can be stated that the group increments in Table 14 are transferable quantities. 

Beck et al. (2004) presented an analysis of the cost-effectiveness of highly active antiretroviral therapy in Canada. They compared the cost-effectiveness from 1991 to 1995 (pre-HAART period) with the period from 1997 to 2001 (HAART period) for non-Aids and Aids groups. For the first group, they calculate total cost of US 4265 in the pre-HAART period and US 9445 in the HAART-period, whereas 66% and 84% were spent on antiretrovirals. The incremental cost per life year gained was US 14,587, that is, the HAART technology is rather cost-effective. For the Aids patients, the total costs were US 9,099 in the pre-HAART period and US 11,764 in the HAART period, whereas 29% were for antiretrovirals in the pre-HAART era and 72% in the HAART era. The incremental cost per life year gained by introducing HAART was US 12,813, so that HAART seems cost-effective in Canada. 

In order to choose the worst conditions, possible substances that are not listed in Part Three were taken, ie substances that were not used for self-ignition increment calculations by regression. Indeed, choosing as examples substances from the database, the results are almost too good to be used in a demonstration. These new substances come from the publication by Hilado quoted before. The table below gives the list of compounds, the estimated ATTest. the AIT found in the publication AITexp, the list of group numbers taken into account for the calculation as well as cyclic corrections and corrections of potential positions. There is no ketone in the list since they were mentiored in the text. 

Schmitz et al. <2001JP090> developed two group increment schemes for converting HF/6-31G(d) and B3LYP/6-31G(d) calculated energies of aliphatic amines to estimations of heats of formation. Application to the pyrrolizidine yielded calculated values of —1.09 (HF) and —1.02 (B3LYP) instead of — 0.93 kcal mob1 (experimental). 

It is shown that the solubility of fullerenes in vegetable oils can be predicted and justified on the basis of the solubility parameters of C60 and C70 and of the glycerol esters of fatty acids. A detailed procedure for the calculation of the solubility parameters of fullerenes and vegetable oils by group increment is reported. 

It is interesting to note that such molar volumes can be calculated also by group increments using the van der Waals molar volume for a carbon atom, which is 6.95 ml/mol (Van Krevelen, 1990). 

Knowing the fullerene molar volume, either the experimental or the calculated value, it is quite straightforward the calculation of the solubility parameter by substituting the tabulated group increments in equation (13.6). 

Being a mixture of different fatty acids esters of glycerol, the calculation with group increment of the solubility parameter of vegetable oils presents some... 

A theoretical justification of the surprising solubility of C60 and C70 fullerenes in vegetable oils has been proposed in terms of solubility parameter of fullerenes and vegetable oils. It has been shown that the solubility parameter of C60 and C70 fullerenes can be calculated by a group increment approach following Van Krevelen... 

An exception is the calculation of formation enthalpies for organic compounds based on group increments and strain energies 131. 

A well-known tool for the estimation of reactivity hazards of organic material is called CHETAH [5]. The method is based on pattern recognition techniques, based on experimental data, in order to infer the decomposition products that maximize the decomposition energy, and then performs thermochemical calculations based on the Benson group increments mentioned above. Thus, the calculations are valid for the gas phase, but this may be a drawback, since in fine chemistry most reactions are performed in the condensed phase. Corrections must be made, but in general they remain small and do not significantly affect the results. 

Table 4.6 provides the functional-group increments that must be added to the appropriate shift values for alkanes given in Table 4.5. For example, we can calculate the 13C shifts for 3-pentanol.

So the additive functions must be discovered the values of the atom group contributions or increments must be derived. This derivation of group contributions is relatively easy when the shape of the additive function is known and if sufficient experimental data for a fairly large number of substances are known. The derivation is mostly based on trial and error methods or linear programming in the latter case the program contains the desired group increments as adjustable parameters. The objective function aims at minimum differences between calculated and experimental molar quantities. 

On the other hand, the volume contribution of structural groups already contains inbuilt information on the influence of the atomic surroundings. As a consequence the Van der Waals volume of the structural units can approximately be calculated as the sum of the Van der Waals volumes of the composing structural groups. Bondi (1964,1968) was the first to calculate the contributions of about 60 structural groups to Vw. Later Slonimskii et al. (1970) and Askadskii (1987) calculated about 100 values of atomic increments in different surroundings. Since the two approaches used the same method of calculation, and nearly equal basic data on the atomic radii, the calculated values for the structural units are approximately equal. In Table 4.2 also the group increments of Vw are shown, next to those of M. By means of these data the Van der Waals volumes of the Structural Units are easily calculated. 

Here is another instance of the extreme model dependency of strain energies in the fluorocarbon series. A strainless C(F)2(C)2 group increment of - 104.9 kcal mol" had earlier been derived ". In principle, one might expect that this increment would be applicable to calculating the strain energy of hexafluorocyclopropane. Applying this value, we concluded that the total strain in the molecule was 80.9 kcal mol" This was even higher than the value calculated by Bernett some years earlier 68.6 kcal mol" We were buoyed by the fact that the endothermicity of equation 18 indicated a strain of... 

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