Substance Classes

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Substance Classes

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Alloy

A substance composed of a mixture of two or more metals or metals and non-metals. At least one metal is required for an alloy. The components of an alloy are present in defined percentages or ranges of percentages. An alloy has an Alloy Expression unless it is a Manual Registration.

Coordination Compound

A substance consisting of a central atom or ion, usually metallic and sometimes nonmetallic, referred to as coordination center surrounded by an array of bound molecules or ions (known as ligands) attached via metallic, coordination, covalent, or dative bonds.

Element

A substance consisting of only one type of element. A member of the element class has only one type of element in its primary molecular formula without DT, or has a primary molecular formula without DT that is “unspecified” and has only one type of element in its alternate molecular formula without DT. A substance with a molecular formula containing hydrogen and some other element does not qualify for this class.

General Derivative

An ester, ether, acetal, or other derivative of a substance, typically a polymer. Members of this class have an 8:GD text descriptor. Will have a General Derivative Functional Group for each defining functional group, though none is required.

Generic Registration

A manual substance, generated for regulatory or Client Services, that doesn't meet normal Registry rules. Generic Registrations are not normally eligible for use in document indexing. Generic Registrations are also Manual Registrations.

Incompletely Defined Substance

A substance where the structure cannot be completely, unambiguously described by a single connection table fragment. Typical unknown information includes substituent attachment points and double-bond locations. One of four types: 1) Unknown point of attachment, represented with an ID node in the Single Component Connection Table (e.g., 116764-39-7). 2) Molform segment: represented with an ID node in the Single Component Connection Table (e.g., 122136-70-3). 3) Loss of water, represented as a Multicomponent Expression with an “incompletely defined water” attribute (e.g., 282541-02-0). 4) Loss/gain of hydrogen, represented as a Multicomponent Expression with an “incompletely defined hydrogen” attribute.

Manual Registration

A substance that cannot be represented by a connection table either due to lack of structure information or Registry system limitations. A Manual Registration does not have a Single Component Connection Table, Multicomponent Expression, Alloy Expression, or Tabular Inorganic Expression. It may be a component of another substance.

Manual Registrations are substances with structural descriptions that cannot be processed by the CAS REGISTRY system to receive a structure connection table. These fall into three general categories:

  • Substances with a complete structure, but which cannot be processed by the CAS REGISTRY system due to their size or complexity.
  • Substances with an unknown or generic structure.
  • Multicomponent substances consisting of components with complete structures and components with unknown or generic structures.

Mineral

A substance that occurs naturally in non-living systems. May be represented as a Tabular Inorganic, Manual Registration, Coordination Compound, Polymer, or Organic/Inorganic Small Molecule. May have a Single Component Connection Table, Tabular Inorganic Expression, or neither.

Mixture

A substance containing multiple components in an unspecified ratio. A mixture is a Multicomponent Expression where each associated Substance Component has a coefficient of "x".

Nucleic Acid Sequence

A polymeric or oligomeric substance consisting of base units of nucleic acids. A nucleic acid sequence will either have a Single Component Connection Table or a Multicomponent Expression, or be a Manual Registration.

Organic/Inorganic Small Molecule

An organic or inorganic substance with a Single Component Connection Table. In addition to substances specifically designated as Organic/Inorganic Small Molecules, all substances not assigned to any other class, or only to Ring Parent should be assigned to Organic/Inorganic Small Molecule.

Polymer

A substance consisting of repeating structural subunits. A polymer may be either a Structural Repeating Unit (SRU) or Monomer-based.

Protein/Peptide Sequence

A polymeric or oligomeric substance consisting of base units of amino acids. A protein/peptide sequence may have a Single Component Connection Table or a Multicomponent Expression, or be a Manual Registration.

Radical Ion

A substance that is a charged (anion or cation) free-radical.

Registered Concept

A substance that is also a Thesaurus Member. Registered Concepts are not normally eligible for use in document indexing. Registered Concepts are also Manual Registrations. If a registered concept is indexable, a Vocabulary Entry URI must be present.

Ring Parent

A substance consisting of only a base ring system. A Ring Parent registration is created for any newly encountered ring system. Ring Parents are used to generate ring system templates for SIG and to establish the base ring name and locants for nomenclature of associated substances. A Ring Parent is created for all newly encountered ring systems unless the substance with the new ring system happens to be the ring parent. Once registered, a Ring Parent is eligible to be indexed. A Ring Parent may be associated with a document or other source but it is not required.

Salt and Compound With

A substance containing multiple components in a specified ratio, usually due to some type of molecular interaction between components. Includes salts, compound with, hydrates, and solvates. A member of this class does not belong to any other class and the Substance number of components attribute has a value of 2 or more.

Subatomic Particle

A particle smaller than an atom. Subatomic Particles are either elementary particles or composite particles. Elementary particles have no definable internal structure. Composite particles are made up of elementary particles. Subatomic Particles are Manual Registrations and have no valid Molform or Alternate Molform.

Tabular Inorganic

An inorganic substance where the composition is defined by a table of components. The components of a tabular inorganic are present in defined (or undefined) ratios. This class is assigned if and only if the substance has a Tabular Inorganic Expression. (A component with a Tabular Inorganic Expression doesn’t qualify.)