Joback group contributions for

TABLE 2-337 Joback Group Contributions for Critical Constants... 

Devotta, S., and V. R. Pendyala, Modified Joback Group Contribution Method for Normal Boiling Point of Aliphatic Halogenated Compounds. Ind. Eng. Chem. Res., 1992 31, 2042-2046. 

The framework of interactive design is entirely built on the premise of additivity of group contributions for the estimation of physical properties. Let us look at some typical illustrations. Table XV shows the estimation of normal boiling points T, and normal melting points T , using Joback s group contribution techniques (Joback and Reid, 1987), along with the... 

Selected Group Contributions for Solubility Parameters (Joback, 1992)... 

Estimation Methods for Critical and Other Properties 257 Table 6.9-1 Joback Group Contribution.s to Pure Component Propertie.s... 

Optimization to Locate Molecular Structure 55 TTie group contributions for use in the above equations from Joback and Reid (1987) are ... 

Table 3.5 Group contributions for estimating Cp with the Joback method.

Critica.1 Properties. Several methods have been developed to estimate critical pressure, temperature, and volume, U). Many other properties can be estimated from these properties. Error propagation can be large for physical property estimations based on critical properties from group contribution methods. Thus sensitivity analyses are recommended. The Ambrose method (185) was found to be more accurate (186) than the Lyderson (187) method, although it is computationally more complex. The Joback and Reid method (188) is only slightly less accurate overall than the Ambrose method, and is more accurate for some specific substances. Other methods of lesser overall accuracy are also available (189,190) (T, (191,192) (T, P ),... 

Enthalpy of Formation The ideal gas standard enthalpy (heat) of formation (AHJoqs) of chemical compound is the increment of enthalpy associated with the reaction of forming that compound in the ideal gas state from the constituent elements in their standard states, defined as the existing phase at a temperature of 298.15 K and one atmosphere (101.3 kPa). Sources for data are Refs. 15, 23, 24, 104, 115, and 116. The most accurate, but again complicated, estimation method is that of Benson et al. " A compromise between complexity and accuracy is based on the additive atomic group-contribution scheme of Joback his original units of kcal/mol have been converted to kj/mol by the conversion 1 kcal/mol = 4.1868 kJ/moL... 

Upon completion of data collection, estimation of the critical properties for the remaining compounds was performed using the group contribution method of Joback as given by Reid, Prausnitz and Poling (24). A comparison of the estimates with experimental data was favorable with average absolute errors of only 0.9%, 6.3 %, and 4.4% for critical temperature (465 compounds), pressure (453 compounds) and volume (345 compounds). 

The compilations of CRC (2-3) Daubert and Danner (4) Domalski and Hearing (6) and Yaws (18-21) were used extensively. Estimates for enthalpy of fusion at the freezing point were primarily based on methods of Bondi (1, entropy), Joback (8, group contribution), and Chickos et al (11, group contribution). 

The metacontribution of the metagroup 2 (see Table VI) in interval representation is [22.42 81.10]. Thus, we can construct Table VII, which shows the metacontributions for each metagroups, displayed in Table V for boiling point 7, reduced boiling point and heat of vaporization A//, b (Joback and Reid, 1987). Using the group-contribution estimation... 

High correlations between two properties indicate the possibility of replacing one with a function of the other. This would enable us to reduce the dimensionality of a design space. One study (Joback, 1984) found that nine physical properties were well approximated by three new properties called factors. Table XVI shows several of the derived physical property estimation techniques, using essentially two of these factors, F, and F. Group contribution estimation techniques were developed for both factors, f, and Fy... 

Input data Molecular structure and one measured vapor pressure value P)),eas, (often at a low pressure). The method requires estimation of and using a group contribution method. The original Pailhes method used the Lytrerson method [Lydersen, A. L., AlChE 21 (1975) 510], but the Joback method is illustrated here for consistency with the previous examples on critical constant estimation. 

One of the most important contributions to this field was provided by Stein and Brown [117], who extended Joback and Reid s group contribution method [122], The authors calculated 85 group contributions and used a nonlinear quadratic equation to correctly predict BP at high temperatures. The authors calculated MAE = 15.5 K for a set of 4426 compounds and predicted another independent set of 6584 compounds with MAE = 20.4 K. The method was further parameterized by Syracuse Research Inc using 6484 compounds and was used in the MPBPVP program [101]. 

The normal boiling point is an easily accessible physical property and has been measured for a large number of substances. In case that it is not available, the normal boiling point can be estimated with group contribution methods, for example, Joback and Reid [4] and Constantinou and Gani [5], analogously to the estimation of the critical point. The estimation formula for the Joback method is... 

Vi is the number of occurrences of group i in the molecule. The values for the particular group contributions are listed on www.ddbst.com. The results for the representation of the data sets are reported to be superior to those obtained with other methods [12]. An evaluation with more than 2000 substances yielded average deviations of 16.5 K for the Joback method and only 1.5 K for the Rarey/Nannoolal method, which demonstrates the superiority of the latter one. 

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