Constitutive fragments

The 2 D-based descriptors are sometimes divided into different types of descriptors such as constitutional, fragment, and functional group-based as well as topological descriptors. 

To overcome these limitations, Rekker and colleagues" > 7 developed a new approach based on the concept of fragments rather than substituents. A compound can be decomposed conceptually into its constitutive fragments. Thereby, its overall lipophilicity can be obtained simply by adding the lipophilic increment of each of the n fragments. Thus, the log P of a compound can be calculated as ... 

Those based on comparing the occurrence of constitutional fragments. 

The distributed multipoles and the polarizabilities were derived from the MO s of the constitutive fragments of Lig-47, namely benzimidazole, methyl-benzene, CTU in an extended conformation, and benzene-connected dioxane. The location of the sp lone-pairs of CTU was determined on the basis of ELF [142] analyses using the TopMod package [143], and is shown in Fig. 1.10 ... 

DFT can be applied to either the entire systems or their constituting fragments. In the former case, the exchange of electrons between the system and its surroundings is analyzed, whereas the latter approach makes it possible to study electron flow within molecules. 

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