Target property

Descriptors have to be found representing the structural features which are related to the target property. This is the most important step in QSPR, and the development of powerful descriptors is of central interest in this field. Descriptors can range from simple atom- or functional group counts to quantum chemical descriptors. They can be derived on the basis of the connectivity (topological or... 

The model building step deals with the development of mathematical models to relate the optimized set of descriptors with the target property. Two statistical measures indicate the quality of a model, the regression coefficient, r, or its square, r, and the standard deviation, a (see Chapter 9). 

Wire and cable insulation based on vulcanizates of PZ has also been studied. Again, low fire risk was the target property, and this was achieved. The need to vulcanize the coating, somewhat modest tensile properties, tensile strength of 5.2 to 12.2 MPa (760 to 1770 psi), and high dielectric constant (4—5 at 10,000 Hz) limited interest in this appHcation (19). 

In this reaction, no by-products are evolved, and the crosslinking reactions occur within the bulk of the material. A typical hydrosilylation crosslinking system is depicted in Scheme 11, where n and y can vary depending on the required viscosity of the uncured formulation and the final targeted properties of the cured adhesive. 

Vaidyanathan, R., and El-Halwagi, M. M. (1996). Computer-Aided synthesis of polymers and blends with target properties. Ind. Eng. Chem. Res., 35,627-634. 

Definition of potential paths for chemical structure changes to improve the targeted properties... 

Table I is a list of physical properties of materials which were of special concern, along with target values felt to indicate useful levels in a particular application. From the beginning it was predicted that one of the biggest problems would be to balance Properties A and E, usually considered mutually exclusive. It was also assumed that Properties B and E were highly correlated. Statistically designed experiments and data analysis were chosen to determine most efficiently the formulations which would give the best combination of all the target properties.

Metal-essential radiopharmaceuticals are those whose targeting properties are inherent in the structure and chemistry of the complex itself rather than a biomolecule whose targeting ability is independent of the attachment of the metal. While this class of tracers includes many well-developed technetium complexes, it includes relatively few rhenium complexes. 

Experiment-based trial and error - This approach is used when mathematical models for the estimation of the desired (target) properties are not available. A large number of consumer products are developed through experiment-based trial and error approaches. In this case, the desired properties need to be measured and consequently, not many candidate molecules can be considered. A list of candidate molecules may however be supplied by an expert or generated from past knowledge and/or experience. A database of chemicals may also be used to generate a list of candidates. 

How to define the goals and needs of a chemical product in terms of a set of desired (target) properties ... 

The basic GC-model of the Constantinou and Gani method (Eq. 1) as presented above provides the basis for the formulation of the solvent replacement problem as a MILP-optimization problem. For purposes of simplicity, in this chapter, only the first-order approximation is taken into consideration (that is, W is equal to zero). In this way, the functions of the target properties of the generated molecules (solvent replacements) are written as monotonic functions of the property values, thereby, leading to a linear right hand side of the property constraints (property model equation), as follows,... 

In Eq. 2, index p indicates a specific target property from the NP number of properties considered, pk is the value of the property k for the given compound and fk(pt) is the corresponding monotonic functional transformation of this value. 

Similar to the previous examples, the pre-selected target properties for the replacement of methylene chloride as a solvent, are listed in Table 3. 

Computer aided molecular design (CAMD) problems are defined as, Given a set of building blocks and a specified set of target properties Determine the molecule or molecular structure that matches these properties. 

In this respect, CAMD technique [Gani et al. (1991)]is the reverse problem of property prediction, where, given the identity of the molecule (or the molecular structure) or a mixture, a set of target properties is calculated. In this chapter,... 

Step 1 Problem Formulation - here, the CAMD problem is defined in terms of target properties (both the identity of the property as well as their target values). 

Step 2 Initial Search - generate initial list of candidates through a search of a database (if available, for example, CAPEC database). This provides a good idea of which types of molecules one should be looking for. Note that the search should be made only with respect to the pure component target properties as a search with respect to mixture properties may not be possible. 

Step 3 Generate and Test - use any CAMD technique (and software, for example, ProCAMD) to automatically generate and test candidates. The selected CAMD technique should be able to generate molecular structures and evaluate their properties with respect to the specified target properties. 

Non-temperature dependent Specify upper, lower, and/or goal values only for the target properties (a collection of 26 properties are available)... 

Estimate the target properties for each generated polymer repeat units and eliminate those that do not match the target property values. For the remaining polymers, evaluate them in terms of the following selection criteria ... 

The polymer repeat unit with the smallest value is the best polymer, in this simple polymer design problems. Table 3 highlights the values for the target properties and the selection criteria for 6 polymer repeat units and the best polymer is highlighted. 

By analyzing the atomic contributions to different target properties like BBB permeability, specific atom-types affecting these properties can be identified. 

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