Formulas and Nomenclature

At first it may seem difficult to learn the formulas and names of the hundreds of chemical compounds used in the introductory chemistry course. Actually the job is not so hard if you start in a systematic way, by learning the atomic building blocks that make up the compounds and the rules for naming the compounds.  

One of the many ways to classify inorganic compounds is into electrolytes, nonelectrolytes, and weak electrolytes. When electrolytes are dissolved in water, the resulting solution is a good conductor of electricity the water solutions of nonelectrolytes do not conduct electricity the solutions of weak electrolytes are very poor conductors. Water itself is an extremely poor conductor of electricity. A flow of current is a movement of electrical charges caused by a difference in potential (voltage) between the two ends of the conductor. 

Inorganic compounds also may be classified as acids, bases, and salts. This classification is particularly useful as a basis for naming the chemicals with which we shall deal. 

The names of the elements (and many of the symbols used to represent them) are traditional, rather than part of a logical system. The electrical charges that the ions usually carry can be reasoned out, but chemists do not work through such reasoning every time they want to use the charges or talk about them they simply know them as characteristic properties. 

Once you have learned the symbols for the elements, you will easily recognize and understand formulas. A formula is the shorthand notation used to identify the composition of a molecule. It includes the symbol of each element in the molecule, with numerical subscripts to show how many atoms of each element are present if there are more than one. For example, the formula for 

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What Do We Need to Know Already This chapter draws on the introduction to organic formulas and nomenclature in Sections C and D, the structure of molecules (Chapters 2 and 3), intermolecular forces (Sections 5.3-5.5), reaction enthalpy (Section 6.13), reaction mechanisms (Sections 13.7-13.9), and isomers (Section 16.7). 

A very interesting comparative X-ray diffraction study of six N-cyclic endocyclic enamines 77147 and 78 to 82 was performed by Dunitz and coworkers144. Structural formulae and nomenclature of these enamines are presented in Scheme 2. In addition, 1,1,2-trimorpholinoethene148 (83) is included. Relevant heavy atom distances of the enamino groups are given in Table 1 and angles in Table 2. These structures (77-83) cover enamines mainly of cyclohexene with pyrrolidino, piperidino and morpholino substituents. 

Structural formulae and nomenclature for experimental X-ray data of tertiary N-cyclic enamines... 

Structural formulae and nomenclature for X-ray determinations of tertiary, secondary and primary P-enaminones... 

Molecular formulae and nomenclature of enamines and corresponding saturated amines for which experimental determination of basicities are reported in Table 16. 

Figure 5. Structure formula and nomenclature for the different tocopherols.

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

The one-one correspondence between symbols (formulas) and nomenclature is very highly developed in inorganic chemistry, and played a great part in the development of the subject. It is only when the more complex ionic structures must be named that it fails and group or radical nomenclature must be substituted. This is an important development, even though it seems simple in retrospect. In establishing an equivalence between ... 

A description of the molecular stereochemistry is also included in both the structural formula and nomenclature. Each ring junction can exist in either a cis or trans conformation, yielding six centers of asymmetry or chirality (C-5, 8, 9, 10, 13, 14). Hence, 64 stereoisomers are possible for the ring system alone. With the C-17 side-chain forming a seventh site of asymmetry, the theoretical number of stereoisomers increases to 128. However, in practice, the isomeric possibilities are restricted by the overall conformational limitations of the ring system. 

Associated with TOXLINE is the CHEMLINE file, which stands for Chemical Dictionary On Line. This file contains the CAS registry number, molecular formulas, and nomenclature for thousands of chemical substances. It can be used to identify names and synonyms of chemical substances that are often necessary as key words to search a data base. 

The function of structural formulas and nomenclature is to unambiguously specify and characterize a molecular species without implying more than is justified by experimental fact about the structure and properties of the species. This task is particularly difficult for reactive intermediates and hence necessitates this preliminary discussion. 

TABLE III Formulas and Nomenclature for Boron Hydrides Described as Poiyhedra with Vertices Removed... 

In this section I review briefly the nature of the vibrational and rotational levels of interest and the corresponding selection rules. My purpose is to make the literature, especially that on which the catalogue of laser lines is based, more accessible. Therefore, although physical principles are discussed, the emphasis is on simple formulae and nomenclature. I restrict the discussion to material commonly encountered in the context of molecular lasers — very good broader accounts of the subject of molecular spectroscopy are widely available [2.1-4]. 

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