Graphs Chemical Abstracts Service

The nomenclature of boron hydride derivatives has been somewhat confusing and many inconsistencies exist in the Hterature. The stmctures of some reported boron hydride clusters are so compHcated that only a stmctural drawing or graph, often accompanied by explanatory text, is used to describe them. Traditional nomenclature systems often can be used to describe compounds unambiguously, but the resulting descriptions may be so long and unwieldy that they are of Htde use. The lUPAC (7) and the Chemical Abstract Service (8) have made recommendations, and nomenclature methods have now been developed that can adequately handle nearly all clusters compounds however, these methods have yet to be widely adopted. Eor the most part, nomenclature used in the original Hterature is retained herein. 

The Morgan algorithm 5> is a device used by the Chemical Abstracts Service for assigning indices to the nodes of constitutional formulas whose H-atoms have been omitted, i. e. their reduced graphs. If the indices of all atoms are needed, e.g. for the representation of stereochemistry, an additional procedure is needed for establishing those for the H-atoms. Constitutional symmetry is not indicated directly by Morgan indices. 

A connection table has been defined [6] as a uniquely ordered list of the node symbols of the structure (or graph) in which the value (atomic symbol) of each node and its attachment (bonding) to the other nodes of the total structure are described , though it does not have to be unique. The Chemical Abstracts Service (CAS) Registry III connection tables [7] are unique, however, and that for hydroquinone is illustrated in Figure 1 ... 

Substructure searches are implemented in standard fashion that is, a fast screen-out is used to get rid of obvious nonmatches, followed by a full atom-by-atom search on the structures that pass the screen. The atom-by-atom search is a backtracking, graph-tracing procedure, resembling those used by Chemical Abstracts Service and Molecular Design Ltd. 

Artificial Intelligence in Chemistry Chemical Abstracts Service Information System Graph Theory in Chemistry Nomenclature Automatic Generation and Conversion Quantitative Structure-Activity Relationships in Drug Design Reaction Databases Ring Perception Stereochemistry ... 

Chemical Abstracts Service Information System Factual Information Databases Graph Theory in Chemistry Online Databases in Chemistry Structure and Substructure Searching. 

Canonical Numbering and Constitutional Symmetry Chemical Abstracts Service Information System Graph Theory in Chemistry Inorganic Three-dimensional Structure Databases Polymers Structural Representation Standard Exchange Formats for Spectral Data Structure and Substructure Searching Structure Databases Structure Representation Three-dimensional Structure Generation Automation Three-dimensional Structure Searching. 

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