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chemical database small molecules "ChemDB". 5,000,000 ChemExper Chemexper Chemical Directory catalogue chemicals CASno Structure SMILES "ChemExper". Chemxpert Database Chemxpert Chemical Database small molecules database buyers,suppliers "ChemxpertDB". 10,00000 Chemical Book East West University: commercially available compounds
The classification of minerals was based on chemical composition by Dana in the fourth edition (1854, in two volumes) of his book System of Mineralogy. [ 5 ] [ 6 ] For the 20th century, this classification was completed thanks to scientific progress, particularly in the field of crystallography .
Unlike other chemical formula types, [a] which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a more complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures ...
Theories of chemical structure were first developed by August Kekulé, Archibald Scott Couper, and Aleksandr Butlerov, among others, from about 1858. [4] These theories were first to state that chemical compounds are not a random cluster of atoms and functional groups, but rather had a definite order defined by the valency of the atoms composing the molecule, giving the molecules a three ...
Different input structures may give the same result; for example, acetic acid and acetate would both give the same core parent structure, that of acetic acid. A core parent structure may be disconnected, consisting of more than one component, in which case the sublayers in the InChI usually consist of sublayers for each component, separated by ...
Chemical classification systems attempt to classify elements or compounds according to certain chemical functional or structural properties. Whereas the structural properties are largely intrinsic, functional properties and the derived classifications depend to a certain degree on the type of chemical interaction partners on which the function is exerted.
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The chemical species can be an atom, molecule, ion, or radical, with a specific chemical name and chemical formula. [ 2 ] In supramolecular chemistry , chemical species are structures created by forming or breaking bonds between molecules, such as hydrogen bonding , dipole-dipole bonds , etc. [ 3 ] These types of bonds can determine the ...