Fragment Connectivity

Fragments used for building fragment descriptors can be connected and disconnected. Most applications are based on connected fragments. The point is 

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On the other hand, acyclic diastereomers are not necessarily compounds without any cyclic structural element, but the fragment connecting the stereogenic centers is acyclic. For example, a bicyclo[2.2.1]heptane derivative with a chiral side-chain attached to a nonbridgehead carbon belongs to this second category of acyclic diastereomers. 

A physical model usually predisposes to physicochemical descriptors, such as p/Ca, log P or molar volume for the whole molecule, or the equivalent descriptors for substituents on a common molecular framework. But different structures can have the same or similar property values, and we are interested in designing structures. So at some stage we must choose structural descriptors (atom types, substructural fragments, connections, or indices from molecular orbital calculations) or at least relate structure to property in order to design the appropriate structure. 

To understand the subtlety and electronic structure of the complex covalent network of /9-R105 boron, it is useful to view the contents of the unit cell [Fig. 13.4.11(b)] as assembled from Bi2fl (at the center of a B84 cluster) and B57 (lying on a C3 axis) fragments connected by 2c-2e bonds. 

Isolobal relationships between main-group and transition-metal fragments. Connections to organometallic chemistry... 

Coal swelling in several organic solvents shows that coal macromolecules are cross-linked. These cross-links are believed to occur by covalent bonds between aromatic molecular clusters with larger fragments connected by donor-acceptor (coordinative) bonds. In the pores of the macromolecular network, coals also contain small organic molecules with MW up to 700 Dalton. 

First-order connectivity indices computed for predefined positions on molecular fragments in congeneric series [Takahashi et al, 1985]. By superimposition of all congeneric compounds, a template structure is derived whose vertices define the positions for the FMC indices the vertices of the common parent structure are not considered in defining the positions. For a k th position the corresponding fragment connectivity index is defined as ... 

A range of di- and trinuclear complexes containing Tp MoOCl fragments connected by bis-or tris-phenolato bridging ligands has been studied by McCleverty, Ward, and co-workers. The... 

The molecular structure of [Ti2Cp4(N3)2](/x-0) has been determined by X-ray diffraction, showing a binuclear complex with two bis-Cp azido fragments connected through the oxygen bridge.1510... 

If such reactions are intramolecular, their transition state may be visualized as an association of two fragments connected at their termini by... 

Syntheses, reactivity, and physical properties of subphthalocyanines (macrocyclic compounds containing three diiminoisoindole fragments connected with a boron atom by N-B bonds) 02CRV835. 

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