Well-Defined Substances

The guidelines for the naming and therefore identity of substances that are well-defined are described in Section 4.2 of the TGD. The 

These examples demonstrate that reaction product mixtures must be evaluated on a case-by-case basis. The rules demonstrated in the examples mentioned above do not cover all possible cases, and registrants are encouraged to contact the authoritative body (ECHA or the individual national authority) if they believe that there is a good reason to deviate from the standard rules. 

Poorly defined substances or of variable composition are defined as UVCB. This designation is comparable with the UVCB category in the US under the Toxic substances Control Act (TSCA). Substances included in this grouping cannot be identified by chemical 

The TGD identifies four subtypes of UVCB chemicals (1) where the source is biological and the process is a synthesis (2) where the source is a chemical or mineral and the process is a synthesis (3) where the source is biological and the process is refinement and (4) where the source is chemical or mineral and the process is a refinement. One very common and simple example of these parameters is if two very well-defined chemicals react with each other, but the chemical identity of the reaction product is not sufficiently known or is poorly predictable. For example, reaction of the dicarboxylic acid nonanedioic acid with 2-amino-2-methyl-l-propanol, a substance with alcohol and amine functionality, can produce multiple products. The amine can reacts with either acid group or both to form amides, the alcohol can react with either acid group or both to form esters, or a combined ester-acid may form. The preferred EINECS name for registration purposes is nonanedioic acid, reaction products with 2-amino-2-methyl-l-propanol, EC number 294-006-2 CASRN 91672-02-5. 

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The reaction described above can also be carried out at higher concentration whereby the probability of intramolecular reaction (cyclization) vanishes. So called chain extension processes result from the stoichiometric reaction of a "living" bifunctional precursors with an efficient bifunctional electrophilic deactivator. This polycondensation reaction induces a very large increase of the molecular weight, but is also results in an enhanced polydispersity. - Fractionation is necessary if well defined substances are required. However the average distance between successive hinges along the chain fluctuates only very little. 

Red phosphorus does not appear to be a well-defined substance but diHcn according to the method of preparation. It probably consists of random chains. The rate of formation is increased by certain substances such as iodine which appear to be incorporated into the product. 

Dilute acids decompose them into two substances one insoluble, amorphous, yellowish, called hemiprotein the other soluble in water, insoluble in alcohol, faintly acid, called hemialbumin. A prolonged boiling with moderately concentrated HjS04 decomposes them, forming well-defined substances—glycocol, leu-cin, tyrosin aspartic and glutamic acids. 

This chapter discusses lUPAC and CAS nomenclature systems and the SMILES notation, along with examples of each. Multiple names for a single well-defined substance—ethyl acrylate—are also presented. 

Jasmolins I and II are chemically well-defined substances which are sufficiently described by their constituents. In such cases, whether the substance is isolated from an extract or synthesised by a chemical process is irrelevant. Therefore, the synthesised mixture of jasmolins I and II can be regarded to be the same as the isomer mixture extracted from the mum oil, even if derived from different manufacturing processes, provided that the purity of the mixture and the concentration range of the main constituents are identical. If jasmolin I and jasmolin II were synthesised separately and then mixed, the individual components would have to be registered separately. 

A. Single entries for well-defined substances or articles including entries for substances covering several isomers, e.g.,... 

THE TERM CRITICAL DATA refers to measured properties of well-defined substances or materials that have been carefully evaluated and organized for convenient use by scientists and engineers. Such collections of data have... 

The sharp bands show that it is a well-defined substance. 

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