SPQR

Quantitative descriptions of the structural dependence of properties are called structure-property quantitative relationships (SPQR). The four types of these relationships are ... 

There are several different types of chemical species (molecules, ions, radicals, car-benes nitrenes, benzynes, etc.) for which SPQR can be determined. Three kinds of structure are possible ... 

The purpose of SPQR is to provide a quantitative description of the change in some measurable quantity Q that occurs when a change is made in the structure of the species by varying the substituent X. All of the other pertinent variables such as the conditions of the measurement are held constant. Thus ... 

Once suitable parameters are available the values of g can be correlated with them by means of either simple linear regression analysis if the model requires only a single variable, or multiple linear regression analysis if it requires two or more variables. Such a correlation results in a SPQR. In this work we consider only those parameters that are defined directly or indirectly from suitable reference sets or, in the case of steric parameters, calculated from molecular geometries. 

Predictive. All SPQR can be used to predict reactivities, chemical and physical properties and bioactivities. There are manifold practical applications of such predictions. Particular examples include the design of bioactive molecules such as medicinal drugs and... 

Archival. SPQR provide a concise, efficient and convenient method for storing the results of experimental studies on the effect of structural changes upon properties. 

They are predictive. Once the SPQR has been determined, the value of the property can be calculated for any chemical species for which the structural effect parameters are available. This makes possible the design of chemical species with specific chemical, physical or biological properties. 

They are explicative. SPQR can be used to explain structural effects on a measured property. In the case of chemical reactivity, they can provide information useful in determining reaction mechanism. 

An alternative method for obtaining SPQR is based on the use of neural networks. ... 

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