Functional group activation

UNIFAC andASOG Development. Pertinent equations of the UNIQUAC functional-group activity coefficient (UNIFAC) model for prediction of activity coefficients including example calculations are available (162). Much of the background of UNIFAC involves another QSAR technique, the analytical solution of groups (ASOG) method (163). 

Myrdal, P. B., Manka, A. M., Yalkowsky, S. H. AQUAEAC 3 aqueous functional group activity coefficients application to the estimation of aqueous solubility. Chemosphere 1995, 30,1619-1637. 

These models are semiempirical and are based on the concept that intermolecular forces will cause nonrandom arrangement of molecules in the mixture. The models account for the arrangement of molecules of different sizes and the preferred orientation of molecules. In each case, the models are fitted to experimental binary vapor-liquid equilibrium data. This gives binary interaction parameters that can be used to predict multicomponent vapor-liquid equilibrium. In the case of the UNIQUAC equation, if experimentally determined vapor-liquid equilibrium data are not available, the Universal Quasi-chemical Functional Group Activity Coefficients (UNIFAC) method can be used to estimate UNIQUAC parameters from the molecular structures of the components in the mixture3. 

Myrdal, P., Ward, G.H., Dannenfelser, R.-M., Mishra, D., Yalkowsky, S.H. (1992) AQUAFAC 1 Aqueous functional group activity coefficients application to hydrocarbons. Chemosphere 24, 1047-1061. 

Source Compiled from S.R. Montgomery, Functional group activity of promoted Raney nickel catalysts, in Catalysis of Organic Reactions, W.R. Moser, Ed., Marcel Dekker, New York, 1981, pp. 383-409. 

Another naturally occurring ribozyme which catalyzes phosphodiester transfer reactions is the hairpin ribozyme. The hairpin ribozyme has been the subject of a number of excellent review articles [24,25]. Several independent studies performed recently have indicated that the hairpin ribozyme has an interesting feature which distinguishes it from the aforementioned ribozymes mechanistically While the HHR, the group I intron, the HDV ribozyme and many other ribozymes that we are going to meet in this review are metalloenzymes and require divalent metal ions in their active sites for functional group activation, divalent metals ions only play a passive role (they are mainly required for cor-... 

Myrdal, P., G. H. Ward, P. Simamora, and S. H. Yalkowsky, AQUAFAC Aqueous functional group activity coefficients , SAR QSAR Environ. Res., 1, 53-61 (1993). 

UNIQUAC functional group activity coefficient universal quasi-chemical [15]... 

Myrdal, P B., A. M. Manka, and S. H. Yalkowsky. 1995. AQUAFAC 3 Aqueous functional group activity coef cients application to the estimation of aqueous solu Dlltp.mospher 0 1619-1637. 

The UNIFAC (UNIQUAC functional group activity coefficient) method is an extension of the UNIQUAC (Universal quasi chemical) method, which has been used widely in chemical process engineering to describe partitioning in organic systems as occur in petroleum and chemical processing (Fredenslund et al., 1975,1977). It has been applied less frequently to aqueous systems. It expresses the activity coefficient as the sum of a "combinational" component, which quantifies the nature of the area "seen" by the solute molecule, and a "residual" component, which is deduced from group contributions. Arbuckle (1983,1986), Banerjee (1985), Banerjee and Howard (1988), and Campbell and Luthy (1985) have tested the applicability of the method to water solubility. 

Myrdal, P.B., G.H. Ward, P. Simamora, and S.H. Yalkowsky. 1993. AQUAFAC Aqueous Functional Group Activity Coefficients. SAR and QSAR in Environmental Research, Vol. 1 53-61. 

Myrdal, P., A.M. Manka, and S.H. Yalkowsky. 1995. Aquafac 3 Aqueous Functional Group Activity Coefficients Application to the Estimation of Aqueous Solubility. Chemosphere. 30, No. 9 1619-1637. 

Lee, Y.-C., Myrdal, P.B., Yalkowsky, S.H. (1996) Aqueous functional group activity coefficients (AQUAFAC). 4 Applications to complex organic compounds. Chemosphere 33(11), 2129-2144. 

Uniquac Functional-group Activity Coefficient (where UNIQUAC = Universal Quasi-Chemical)... 

Another group contribution method that has been applied to the prediction of soil sorption is the UNIquac Functional-group Activity Coefficient (UNIFAC, where UNIQUAC = Universal Quasichemical) approach (Fredenslund et al., 1977). Ames and Grulke (1995) applied the method to a small diverse set of chemicals, with rather poor results. They did not report any correlations, but from their results it can be shown that the correlation of observed and predicted log values using the Bondi method was n = 17, R2 = 0.571, 5 = 0.524, and F = 20.0 eight chemicals were predicted with an error of < 0.5 log units, 7 chemicals were predicted with an error between 0.5 and 1.0 log units, and 2 chemicals were predicted with an error of > 1.0 log units. 

The UNIFAC computer program (UNIversals quasichemical Functional group Activity Coefficients) has received broad acceptance throughout the profession... 

The UNIFAC (Unified quasi chemical theory of liquid mixtures Functional-group Activity Coefficients) group-contribution method for the prediction of activity coefficients in non-electrolyte liquid mixtures was first introduced by Fredenslund et al. (1975). It is based on the Unified Quasi Chemical theory of liquid mixtures (UNIQUAC) (Abrams and Prausnitz, 1975), which is a statistical mechanical treatment derived from the quasi chemical lattice model (Guggenheim, 1952). UNIFAC has been extended to polymer solutions by Oishi and Prausnitz (1978) who added a free volume contribution term (UNIFAC-FV) taken from the polymer equation-of-state of Flory (1970). 

UNIFAC UNIfied quasi chemical theory of liquid mixtures Functional-group Activity Coefficients 4.3.2... 

Phenol groups are determined by the difference of the neutralization reactions between sodium hydroxide and sodium carbonate which are common for carboxylic and phenolate groups. Oxidized carbons (typically in air at 700 K) contain equal amounts of these two functional groups. Activated carbons contain up to 800/zeqg-1 carbon of phenolate groups. The volumetric determinations are also sensitive to both carboxylic and phenolate groups so that specific deri-vatization processes are needed to reliably discriminate the two types of groups. 

UNIQUAC Functional-group Activity Coefficients proposed by Aa.Fredenslund, R. L. Jones, and J.M. Prausnitz, AIChE J.,vol. 21, p. 1086—1099,1975 given detailed treatment in the monograph Aa. Fredenslund, J. Gmehling, and P. Rasmussen, Vapor-LiquidEquilihrium using UNIFAC, Elsevier, Amsterdam, 1977. 

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