Semiquantitative prediction

Although, for obvious reasons, classical thermod5mamics caimot provide a quantitative account of the vast variety of phenomena occurring on the nanoscale, it does make some useful semiquantitative predictions in the scalable size interval. For example, based on the Gibbs-Thompson relation, Pheth predicted that for a metal composed of small particles, the redox potential E d) of the transition... 

The take-home lesson is that independent electron treatments, e.g. the HMO model, should be used with caution, especially if semiquantitative predictions are intended. Warning Concerning limitations and possible side-effects consult your PE spectroscopist or your neighbour theoretician. 

In the field of alloy surface composition, both theory and experimental determination achieved much progress in recent years. The present state of the art does not, unfortunately, allow one to predict quantitatively the surface composition from the bulk concentrations, but calculations on models allow one to estimate various effects and to make interesting conclusions and sometimes even semiquantitative predictions. 

Consequently, with the present knowledge of reductive dehalogenation reactions of Cr and C2-compounds, and considering the quality of the various molecular descriptors, only qualitative, or at most semiquantitative, predictions of the relative reactivities of a confined set of structurally related compounds in a given system are possible. Nevertheless, evaluation of such relative reactivities in different systems may provide important insights into such reactions, which will be demonstrated by the following two examples. These two examples will, however, also illustrate the... 

Most gaseous fuels as well as some liquid fuels contain no or only small amounts of chemically bound nitrogen. In combustion of these fuels, the important source of NO is fixation of N2 in the combustion air. Molecular nitrogen, with its triple bond, is very stable, and only very reactive radicals may succesfully attack N2. The mechanisms of NO formation from N2 is quite well understood [274], and for many applications semiquantitative predictions of NO are within reach. 

In spite of the potential advantages, useful organic NLO materials have not yet been developed because the necessary molecular and macroscopic characteristics have only recently begun to be understood. However, because bulk NLO properties in organic materials arise directly from the constituent molecular nonlinearities, it is possible to decouple molecular and supramolecular contributions to the NLO properties. One can then semiquantitatively predict relative macroscopic nonlinearities based on theoretical analyses of the individual molecules (7). Reliable predictions of this kind are vital for the efficiency of a program aimed towards developing new organic materials with tailored NLO properties. 

To predict whether the substance is particularly sensitive to oxidation or not (semiquantitative prediction)... 

The above model makes qualitative and semiquantitative predictions about the IVR and VP rates in different clusters. Of particular relevance is the comparison of the IVR and VP rates for the clusters aniline(CH4)1, aniline(N2)i, and aniline(Ar)1 aniline(Ar)1 has only the three vdW modes aniline(CH4)1 has six vdW modes and anilinefN has five vdW modes. As a result, the sums and densities of vdW states used in the calculations of fcIVR and kVP are quite different in these three clusters. Since the chromophore in these clusters remains the same, however, initial excitation to roughly the same energy in each cluster is possible. Furthermore, we expect that the extent of chromophore-solvent interaction will not be vastly different in these cases that is, the A term in eq. (5-2) will be of the same order of magnitude for each cluster. The IVR rates for the N2 cluster are expected to fall below those of the CH4 cluster but above those of the Ar cluster... 

In order to extrapolate the laboratory results to the field and to make semiquantitative predictions, an in-house computer model was used. Chemical reaction rate constants were derived by matching the data from the Controlled Mixing History Furnace to the model predictions. The devolatilization phase was not modeled since volatile matter release and subsequent combustion occurs very rapidly and would not significantly impact the accuracy of the mathematical model predictions. The "overall" solid conversion efficiency at a given residence time was obtained by adding both the simulated char combustion efficiency and the average pyrolysis efficiency (found in the primary stage of the CMHF). 

There have been numerous attempts to compare equations such as (XIV.10.23) with experiment and also to obtain other equations which involve explicitly the mechanism of flame propagation by diffusion of free radicals. It is doubtful, however, if the theory as currently formulated [for example, Eq. (XIV.10.23)] can be used for anything other than qualitative or semiquantitative prediction, particularly in view of the complex-... 

Elementary electrostatic theory cannot account for the observed ionization equilibria in nonaqueous solvents. The functional approach provides a qualitative interpretation of all ionization phenomena, and this is in agreement with quantum mechanical results. This approach considers the coordinating properties of the solvents toward neutral solutes, cations, and anions and takes into account outer-sphere Coordination occurring both in the pure solvents and in the solutions. The application of the donicity and of other phenomenological properties allows a number of semiquantitative predictions. 

The orbital tilting argument implies that the size of the dienophile should have no influence on the diastereoselectivity, hence variations in stereoselectivity with different dienophiles could not be explained. More recently an explanation based on torsional and steric effects has been advanced that permits predictions of stereoselectivities for as yet unstudied cases. A computational model has also been developed to provide semiquantitative predictions of stereoisomer ratios in reactions of substituted species118. 

Bassoli, A., Drew, G. B. D., Merlini, L., Morini, G. General pseudoreceptor model for sweet compounds a semiquantitative prediction of binding affinity for sweet-tasting molecules. J. Med. Chem. 2002, 45, 4402-4409. 

A CA approach described zinc adsorption on aquifer sand material from Cape Cod by assuming that the aluminum and iron phases present in the quartz grain coatings have a surface area and site density similar to those of poorly crystalline materials (Davis et al., 1998). A similar approach provided only a semiquantitative prediction of uranium adsorption on an alluvial aquifer sediment from Naturita, Colorado, depending on the assumptions made about the relative amounts of surface area of quartz, ferrihydrite, and goethite (Davis et al., 2004). In both of these studies, the surface complexation model considered... 

Such cubic equations of state as van der Waals correlate very satisfactorily the UCST-type behavior for polymers solutions, as shown by Harismiadis et al. ° A generalized correlation of the interaction parameter of the van der Waals equation of state for polymer blends based exclnsively on polystyrene blends has been presented. By nsing this equation, the van der Waals eqnation of state can be used as a predictive tool for investigating the compatibility of polymer blends. Predictive GC thermodynamic methods such as Entropic-FV, GC-Flory, UNIFAC, and UNIFAC-FV perform rather poorly, at least from a quantitative point of view. Entropic-FV performs best among these models, on a qualitative basis. For semiquantitative predictions in polymer blends, the approach proposed by Coleman et al. is recommended. 

P and S amino derivatives exemplify the decrease of the On value associated with an increase of the third-row element valency. This finding allows a semiquantitative prediction of an essentially pyramidal (onj of ca. 107°) configuration of the N atom in amides of chloric acid, similar to its configuration in chloroamines. 

The coefficients from Table 2-1 and atomic term values from Table 2-2 will suffice for calculation of an extraordinarily wide range of properties of covalent and ionic solids using only a standard hand-held calculator. This is impressive testimony to the simplicity of the electronic structure and bonding in these systems. Indeed the same parameters gave a semiquantitative prediction of the one-electron energy levels of diatomic molecules in Table 1-1. However, that theory is intrinsically approximate and not always subject to successive correc-... 

As mentioned on p. 7, qualitative and semiquantitative predictions about conformer stabilities can be made based on perturbation treatments in the context of one-electron MO theory. The technique is very well described by Epiotis et al. (1977). Stabilizations and destabilizations are analysed in terms of pairwise interactions between MOs. In the following discussions (Sections 4 and 5) we shall only mention stabilizing interactions, which take place between occupied (bonding or nonbonding) and vacant (antibonding) orbitals. If overlap is neglected then the stabilization A is given by... 

The iterative maximum overlap approximation (IMOA) method is useful for the semiquantitative prediction of the geometry of hydrocarbons, and has been applied... 

The contact angles of water and suitable solvents at the solid/liquid/gas interface allow the determination of the surface tension of solids as well as the dispersive (y ) and polar (yP) components. A semiquantitative prediction of the hy-drophilicity and hydrophobicity of polymer surfaces has already been achieved by contact angle determination with water [74,75]. 

---