Structure formula Beilstein database

The number of theoretically possible chemical structures for a given molecular formula can be very large. For example, a structure generator could generate more than 151 million isomers for a molecule with the molecular formula C6H5N4O (mass =150 Da). In contrast, the Beilstein database of organic compounds contains only 273 structures for this molecular formula [4]. 

The following table contains numbers IM I of constitutional isomers for given mass m and moleculen formula /S with elements in 4 and containing at least one C atom. Column BS contains the number of such isomers contained in the Beilstein database (Section 2.5), while column MS refers to the MS structure database introduced in Subsection 8.3.4. Cleeu-ly, these numbers of isomers found in the databases are snapshots, they may have changed in the meantime. Nevertheless they seem to be of interest in order to show the enormous difference between the mathematically possible nmnbers cuid the amount of compounds that were shown to exist, including corresponding mass spectra. For more detail see Section 2.5 and [152]. 

The Beilstein CrossFire Organic Chemistry Database provides worldwide coverage of the literature relating to the preparations and properties of organic compounds. Beilstein is searchable in multiple ways, including chemical structure, formula, and physical property parameters. Beilstein indexes periodicals, books, dissertations, and patents dated 1800 to the present. 

This is, however, the most serious problem of database-based structure elucidation. Even the largest databases contain only tens of thousands or a few hundred thousand spectra to date. Thus, in the MS database NISTll [226], used in parts of the present work, there are 243,893 El-MS spectra belonging to 212,961 compounds. The database Beilstein used in Section 2.5 contains 8,711,107 known organic compounds, while the number of mathematically possible constitutions, even for a single molecular formula of low mass (about 150 Da), can exceed 100 million (see Appendix D). For example, the smallest (with respect to molecular mass) molecular formula associated with more than 100 million mathematically possible constitutions is Cg N2 0 (146 Da, 109,240,025 isomers). 

While the Beilstein file contains a good deal of data in this area, there are also excellent compilations dedicated to thermodynamic quantities. DETHERM is produced by Dechema, and contains thermophysical properties for ca. 17000 compounds and mixtures (see Chemical Engineering Databases). The subject matter is taken from phase equilibria, PVT behavior, thermodynamic quantities, transport phenomena, surface properties, and electrolyte properties. Attention must also be drawn to the compilations of the US National Institute of Standards and Technology (NIST). The NIST Chemistry WebBook contains thermodynamic data for over 5000 compounds and ion energetics data for over 10000 compounds. The user may search on specific compounds based on name, chemical formula, or CAS Registry Number. Structures are given for all species, as well as common and commercial names. 

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