Systems of nomenclature

Although epoxides are always considered to have their oxygen atom as part of a three membered ring the prefix epoxy in the lUPAC system of nomenclature can be used to denote a cyclic ether of vanous sizes Thus... 

Several systems of nomenclature have been used for naphthalene, and many trivial and trade names are well estabUshed. The Chemicaly hstracts Index Guide is employed in this article. The numbering of the naphthalene nucleus is shown in (1) older practices are given in (2) and (3). 

In the days of alchemy and the phlogiston theory, no system of nomenclature that would be considered logical ia the 1990s was possible. Names were not based on composition, but on historical association, eg, Glauber s salt for sodium sulfate decahydrate and Epsom salt for magnesium sulfate physical characteristics, eg, spirit of wiae for ethanol, oil of vitriol for sulfuric acid, butter of antimony for antimony trichloride, Hver of sulfur for potassium sulfide, and cream of tartar for potassium hydrogen tartrate or physiological behavior, eg, caustic soda for sodium hydroxide. Some of these common or trivial names persist, especially ia the nonchemical Hterature. Such names were a necessity at the time they were iatroduced because the concept of molecular stmcture had not been developed, and even elemental composition was incomplete or iadeterminate for many substances. 

This system of nomenclature has withstood the impact of later experimental discoveries and theoretical developments that have since the time of Guyton de Morveau and Lavoisier greatiy altered the character of chemical thought, eg, atomic theory (Dalton, 1802), the hydrogen theory of acids (Davy, 1809), the duahstic theory (Berzehus, 1811), polybasic acids (Liebig, 1834), Periodic Table (Mendeleev and Meyer, 1869), electrolytic dissociation theory (Arrhenius, 1887), and electronic theory and modem knowledge of molecular stmcture. 

Substitution (see Seetion 1.02.9.1.1) is the formal proeedure most widely applied in modifying parent names. Indeed, the general term substitutive nomenclature is often used to describe the system of nomenclature in which substitution is the main operation. A fundamental concept of this system is that of the principal characteristic group . 

During the World War II the United States Government introduced the following system of nomenclature which continued in use, at least partially, until the 1950s and is used in many publications of the period. 

The following is an example of the application of this system of nomenclature. Strychnidine (p. 564) is oxidised by chromic acid to 2 8-diketo-... 

The newer (R,S) system of nomenclature is superior to the older d,l system in one important way. The configuration of molecules with more than one... 

The systematic nomenclature used originally the term imidazo-1,2,3-triazine. The Chemical Abstracts indexes use the more accurate name imidazo[4,5-d]-Z -triazine (141). The numbering of the substituents is different in the two systems of nomenclature as may be seen in the formulas. 

The same system of nomenclature can be used to differentiate tautomers of types 22 and 23, which would be named 4-methyl-IH-imid-azole and 4-methyl-3//-imidazole, respectively. 

Chemical Abstracts), and a-carboline is sold commercially under the name 1-azacarbazole. The trivial norharman nomenclature, in conjunction with numbering as in 1 or as in 6, is still to be found in recent papers. Other systems of numbering, as well as some incorrect systems of nomenclature, are to be found and add to the confusion. 

In the most commonly used system of nomenclature, each polymer is represented by a letter, which iden-... 

As the science of organic chemistry slowly grew in the 19th century, so too did the number of known compounds and the need for a systematic method of naming them. The system of nomenclature we ll use in this book is that devised by the International Union of Pure and Applied Chemistry (IUPAC, usually spoken as eye-you-pac). 

A chemical name typically has four parts in the IUPAC system of nomenclature prefix, locant, parent, and suffix. The prefix specifies the location and identity of various substituent groups in the molecule, the locant gives the location of the primary functional group, the parent selects a main part of the molecule and tells how many carbon atoms are in that part, and the suffix identifies the primary functional group. 

The ortho, meta, para system of nomenclature is also useful when discussing reactions. For example, we might describe the reaction of bromine with toluene by saying, "Reaction occurs atthe para position"—in other words, at the position para to the methyl group already present on the ring. 

UPAC system of nomenclature (Section 3.4) Rules for naming compounds, devised by the International Union of Pure and Applied Chemistry. 

Porphyrins are formally derived from the porphin (1) nucleus by substitution of some or all peripheral positions with various side chains. In the classical system of nomenclature T, introduced by H. Fischer,Sc the peripheral /5-pyrrolic positions are numbered front 1 to 8 and the methine positions (also named meso positions) between the pyrrole rings are designated a, //, y, and 5. The rings are lettered clockwise A, B, C, and D. The classical nomenclature was in the past more and more displaced by a nomenclature which numbers all the carbon... 

Figure 8.3 Examples of different biological effects of enantiomers. S and R refer to a particular system of nomenclature used to describe chiral carbon, (see Appendix A8.1)...

A system of nomenclature has been devised to describe optical isomers conveniently. These isomers differ in configuration and we have to be able to specify the configuration at the asymmetric atom unambiguously. 

Just as we did for PCR, we must determine the optimum number of PLS factors (rank) to use for this calibration. Since we have validation samples which were held in reserve, we can examine the Predicted Residual Error Sum of Squares (PRESS) for an independent validation set as a function of the number of PLS factors used for the prediction. Figure 54 contains plots of the PRESS values we get when we use the calibrations generated with training sets A1 and A2 to predict the concentrations in the validation set A3. We plot PRESS as a function of the rank (number of factors) used for the calibration. Using our system of nomenclature, the PRESS values obtained by using the calibrations from A1 to predict A3 are named PLSPRESS13. The PRESS values obtained by using the calibrations from A2 to predict the concentrations in A3... 

Some older systems of nomenclature are still in use. For example, some cations were once denoted by the endings -ous and -ic for the ions with lower and higher charges, respectively. To make matters worse, these endings were in some cases added to the Latin form of the element s name. Thus, iron(II) ions were called ferrous ions and iron(III) ions were called ferric ions (see Appendix 3C). We do not use this system in this text, but you will sometimes come across it and should be aware of it. 

IUPAC Commission on Nomenclature of Organic Chemistry, Revision of the extended Hantzsch-Widman system of nomenclature for heteromonocycles, Pure Appl. Chem., 55, 409-416 (1983). 

Walker, C.H. (1989). The development of an improved system of nomenclature and classification of esterases. In E. Reiner, W.N. Aldridge, and F.C.G. Hoskin (Eds.) Enzymes Elydrolysing Organophosphorous Compounds, Chichester Ellis Harwood. 53-64. 

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