Chemical formulae and nomenclature

TABLE 8.1. Nomenclature, chemical formulae, and chemical structure of sulfur mustard... 

Monographs provide specific tests, analytical procedures, and acceptance criteria for determining the strength, quality, purity, and potency for a given compendial article. Additional information such as storage conditions, nomenclature, chemical formulae, and the applicable USP Reference Standards are also included in the monograph. 

TABLE 8.1 Nomenclature, Chemical Formulae, and Chemical Structure of Sulfur Mustard... 

Table 1. Chemical formulae and nomenclature of the materials under study...

For the use of atomic symbols to indicate isotopic modification in chemical formulae and the nomenclature of isotopically modified compounds see Section IR-4.5 and Chapter II-2 of Ref. 4 respectively. 

To find information about a particular substance, you must know its chemical formula and name. The names and formulas of compounds are essential vocabulary in chemistry. The naming of substances is called chemical nomenclature from the Latin words nomm (name) and calare (to call). 

Figure 1 Fatty-acid structure and nomenclature. (A) Chemical formula and carbon atom numbering system for a 16-carbon saturated fatty acid (16 0). (B) Schematic representation of 16 0. (C) A monounsaturated fatty add, 18 1n-9, showing the double bond nine carbon atoms from the methyl end (carbon 18). (D) The essential n-6 fatty acid 18 2n-6, where the first double bond is found six carbon atoms from the methyl end. The two double bonds are separated by a methylene (-CH2-) group. (E) The essential n-3 fatty acid 18 3n-3, where the first double bond is found three carbon atoms from the methyl end. (F) Phytanic acid, a dietary / -methyl-branched-chain fatty acid (3,7,11,15-tetramethyl 16 0). The melhyl group on carbon 3 prevents this fatty acid from degradation by /3-oxidation. (G) Pristanic acid (2,6,10,14-tetramethyl 15 0) is the product of phytanic acid o-oxidation, in which a single carbon (carbon 1) is lost. The methyl group on carbon 2 does not preclude subsequent degradation by /3-oxidation.

Two-Dimensional Representation of Chemical Structures. The lUPAC standardization of organic nomenclature allows automatic translation of a chemical s name into its chemical stmcture, or, conversely, the naming of a compound based on its stmcture. The chemical formula for a compound can be translated into its stmcture once a set of semantic rules for representation are estabUshed (26). The semantic rules and their appHcation have been described (27,28). The inverse problem, generating correct names from chemical stmctures, has been addressed (28) and explored for the specific case of naming condensed benzenoid hydrocarbons (29,30). 

Five different structures may be written for the oxazolones. Their skeletal formulas, the Chemical Abstracts nomenclature (listed first), and the names with more common usage follow. 

Alkanes are a class of saturated hydrocarbons with the general formula C H2n. -2- They contain no functional groups, are relatively inert, and can be either straight-chain (normal) or branched. Alkanes are named by a series of IUPAC rules of nomenclature. Compounds that have the same chemical formula but different structures are called isomers. More specifically, compounds such as butane and isobutane, which differ in their connections between atoms, are called constitutional isomers. 

In Chemical Abstracts and in Beilstein specific azo compounds are found under the heading diazenes . As their systematic nomenclature may be very complex (polyazo dyes ), it is much easier to search for them with the aid of the Formula Index of Chemical Abstracts. 

A major part in the language of chemistry is in learning the names of the chemicals (nomenclature). Many chemicals, particularly the more common ones, are known by several different names. For example, the chemical CH3CH2OH has the systematic name ethanol. The publication Chemical Abstracts (American Chemical Society) also uses the name ethanol. The historical or common name is ethyl alcohol or grain alcohol. A nickname for it is just alcohol, and there are various tradenames, depending on the manufacturer. For example, the Fastman Company sells it under the name of Tecsol . Fven trained chemists have trouble with nomenclature, which makes the use of and need for written chemical formulae common among chemists. 

ChemIDplus. Published by the U.S. National Library of Medicine, ChemIDplus [62] is a web-based search system, http //chem.sis.nlm.nih.gov/ chemidplus/, that provides free access to structure and nomenclature authority files used for the identification of chemical substances cited in National Library of Medicine (NLM) databases. ChemIDplus also provides structure searching and direct links to biomedical resources at NLM and on the Internet. The database contains over 349,000 chemical records, over 56,000 of which include chemical structures, and is searchable by name, synonym, CAS registry number, molecular formula, classification code, locator code, and structure. 

Introduction to organic chemistry hydrocarbons and functional groups (structure, nomenclature, chemical properties). Physical and chemical properties of simple organic compounds should also be included as exemplary material for the study of other areas such as bonding, equilibria involving weak acids, kinetics, colligative properties, and stoichiometric determinations of empirical and molecular formulas. 

This overview covers some of the rules for naming simple inorganic compounds. There are additional rules, and some exceptions to these rules. The first part of this overview discusses the rules for deriving a name from a chemical formula. In many cases, the formula may be determined from the name by reversing this process. The second part examines situations in which additional information is needed to generate a formula from the name of a compound. The transition metals present some additional problems therefore, there is a section covering transition metal nomenclature and coordination compounds. 

Graphic representations (chemical formulae) of macromolecules are used extensively in the scientific literature on polymers including lUPAC documents on macromolecular nomenclature. This document establishes rules for the unambiguous representation of macromolecules by chemical formulae. The rules apply principally to synthetic macromolecules. Insofar as is possible, these rules are consistent with the formulae given in lUPAC documents [2-4] and they also cover the presentation of formulae for irregular macromolecules [5], copolymer molecules [1, 6] and star macromolecules. 

Several names have been used in the chemical literature for pyrrolo[l,2-a]pyridine including pyrrocoline, pyrindole, pyrrodine and 8-pyrrolopyridine, but the one which is now used by Chemical Abstracts, and which will be used in this chapter, is indolizine. The numbering of the system is shown in formula (1). The denomination of aza derivatives follows the replacement nomenclature system, e.g. 1-azaindolizine, etc. It should be noted that Chemical Abstracts follows the systematic fusion nomenclature 1-azaindolizine, for instance, is imidazo[l,2-a]pyridine. The cyclazine nomenclature is treated in Section 3.08.9.1. 

Introduction and Orientation, Matter and Energy, Elements and Atoms, Compounds, The Nomenclature of Compounds, Moles and Molar Masses, Determination of Chemical Formulas, Mixtures and Solutions, Chemical Equations, Aqueous Solutions and Precipitation, Acids and Bases, Redox Reactions, Reaction Stoichiometry, Limiting Reactants... 

The oldest publications in this field are mainly concerned with the hydrolysis of hexachlorodisilane and octachlorotrisilane166,167, 417, 4,8> S15 xhe chemical and physical properties of the compounds are well described, but it now seems necessary to revise the postulated structural formulas and the nomenclature (e.g. siliconoxalic acid and siliconmesocalic acid). Exact structural formulae have yet to be ascertained, but the structure certainly includes Si 2 and Si 3 units condensed with Si-O-Si bonds. Depending upon the reaction conditions and water content, more or fewer OH groups will be found in the compound. However, in no case are the double bonds Si = Sid or Si = 0, which had been postulated in earlier publications, found to be present. 

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. 

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