Inventory complex reaction products

With a 13C label at the methide center, the presence of reactive methide intermediate can be verified and complex reaction products can be inventoried and eventually identified. The only limitations are the synthesis and cost involved in incorporation of the 13C label. As a rule we, only use 13C-labeled dimethylformamide and NaCN as starting materials because of their low cost and availability. Another limitation of enriched 13C-NMR monitoring is dilution of the enriched label to natural abundance levels. Currently, we are developing isotope-editing techniques that utilize unnatural 13C double labels to solve this problem. 

The TSCA Inventory provides an overall picmre of the organic, inorganic, polymers, and UVCB (chemical substances of Unknown, or Variable Composition, Complex Reaction Products, and Biological Materials) chemicals produced, processed, or imported for commercial purposes in the United States. The Inventory is not a list of chemicals based on toxic or hazardous characteristics, since toxicity/hazard is not a criterion for inclusion in the list. The Inventory includes chemical substances of any commercial use in the United States since 1979 under the Environmental Protection Act, and is prepared by the US-EPA. The current TSCA Inventory contains approximately 81,600 chemicals. Currently, OPPT is focusing on a subset of approximately 3,000 HPV... 

In most existing inventories, chemical identities are standardized through the use of CAS numbers, molecular formulas (chemicals with discrete structures), and IUPAC (International Union of Pure and Applied Chemistry) systematic nomenclature. Chemicals of unknown or variable composition, complex reaction products, and biological materials (UVCB), are usually listed alphabetically under subheadings or by definition.14 Some of the countries that have compiled various inventories include Australia, Canada, EU, Japan, Philippines, South Korea, and United States. 

See, e.g.. Toxic Substances Control Act Inventory Representation for Combinations of Two or More Substances Complex Reaction Products, available at http //www.epa.gov/oppt/ newchems/pubs/rxnprods.txt. 

UVCB substances are substances of unknown or variable composition, complex reaction products, and biological materials that cannot be represented by unique structures and molecular formulas. Some UVCB substances are not adequately described by their CA Names and have supplemental definitions that are considered integral parts of the names for TSCA purposes. The guidance, entitled Toxic Substances Control Act Inventory Representation For Chemical Substances Of Unknown Or Variable Composition, Complex Reaction Products And Biological Materials UVCB Substances points out that any substance that matches a CA Name but is not covered by the substance description is not considered to be covered by that Inventory listing. 

The guidance on how to name complex reaction products is entitled Toxic Substances Control Act Inventory Representation for Combinations of Two or More Substances Complex Reaction Products. It applies only to chemicals made by a chemical reaction, and not to formulated mixtures, which are made simply by mixing with no chemical reaction. Its primary purpose is to explain when complex reaction products should be named as one reaction product, or as a series of individual components. 

In general, a complex reaction product should be given a single substance name if it is not a polymer and it is a Class 2 substance. Even if the reaction product is composed of numerous types of molecules, one name should encompass all of them. If there is uncertainty about the components of a reaction product, or if the components may vary for each batch, the reaction product is generally named by reference to the products of a reaction or by reference to the reactants, with specified exceptions given in the guidance. If each of the reaction products can be unambiguously identified, and form each time the reaction is run, then the reaction product is classified as a mixture and each component should be separately named and listed on the Inventory. 

Toxic Substances Control Act Inventory Representation For Chemical Substances Of Unknown Or Variable Composition, Complex Reaction Products And Biological Materials UVCB Substances UVCB Substances... 

Most countries with chemical inventories have excluded by-products, small product tests and laboratory quantities, and naturally occurring substances from their reporting schemes. One of the issues associated with inventories is the definition of a chemical. The definition of polymers is a complex issue that will vary depending upon the nature of the chemicals from which they are formed, their relative proportions, the order of reaction, and reaction conditions (duration, temperature, catalysts, etc.).14 Most inventories include polymers and treat all different polymeric substances and monomers as individual chemicals. Some countries, including the United States, have decided not to require updated reporting on the production of such polymers. None of the national chemical inventories include formulated mixtures, or preparations, such as paints and household cleaners, or articles such as automobiles, computers, and paper. 

Figure 10. Proton inventory of cytochrome P450cam second electron transfer and oxygen activation. Rates were normalized relative to the rates of second electron transfer through product release measured in H2O. All data points represent at least three independent determinations of stopped-flow spectrophotometric experiments between dioxygen complexed P450cam (2 iM) and reduced Pd (20 pM) with 2.5 mM metyrapone to stop reactions following single turnover. Reactions were maintained at 8T in D2O/ H2O buffer mixtures listed as mole fraction D2O (n). Data taken from [101].

---