Nomenclature simple compounds

For simple compounds the main reference uses the systematic I.U.P.A.C. nomenclature, but other nomenclature is cross-referenced to the systematic name. 

The systematic lUPAC nomenclature of compounds tries to characterize compounds by a unique name. The names are quite often not as compact as the trivial names, which are short and simple to memorize. In fact, the lUPAC name can be quite long and cumbersome. This is one reason why trivial names are still heavily used today. The basic aim of the lUPAC nomenclature is to describe particular parts of the structure (fi agments) in a systematic manner, with special expressions from a vocabulary of terms. Therefore, the systematic nomenclature can be, and is, used in database systems such as the Chemical Abstracts Service (see Section 5.4) as index for chemical structures. However, this notation does not directly allow the extraction of additional information about the molecule, such as bond orders or molecular weight. 

The nomenclature convention suggested by Pedersen for the simple compounds involves two numbers. The first of these indicates the total number of atoms in the macrocycle. The second number indicates how many heteroatoms are present in the ring. Compound 3 shown above, for example, contains fifteen atoms in the ring, five of which are oxygen. The commonly accepted name for this compound is 15-crown-5 . The three compounds shown below can all be named by this simple rule. 

It is anticipated that readers will already be familiar with many of the general principles of nomenclature and will be able to name a range of simple compounds. It is not the object of this section to provide an exhaustive series of instmctions for naming every class of compound. Instead, the examples chosen here (Box 1.1) have been selected to illustrate some of the perhaps less familiar aspects that will be commonly encountered, and to foster a general understanding of the approach to nomenclature. 

Nomenclature may be the least important of the organic chemists necessary skills, but giving R or 5 designation to simple compounds does matter. These three check your basic knowledge of the rulef... 

Judging from the number of incorrect names that appear in the chemical literature, it s probably safe to say that relatively few practicing organic chemists are fully conversant with the rules of organic nomenclature. Simple hydrocarbons and monofunctional compounds present few difficulties because the basic rules for naming such compounds are logical and easy to understand. Problems, however, are often encountered with polyfunctional compounds. Whereas most chemists could correctly identify hydrocarbon 1 as 3-ethyl-2,5-dimethylheptane, rather few could correctly identify poly functional compound 2. Should we consider 2 as an ether As an ethyl ester As a ketone As an alkeae It is, of course, all four, but it has only one correct name ethyl 3-(4-methoxy-2-oxo-3-cyclohexenyl)propanoate. 

However, the very simplicity of the a nomenclature leads some of its proponents to extend it to simple compounds such as 3-thiapentane for ethyl sulfide. 

In order to steer clear of metaphysical speculations about the ultimate nature of matter, Lavoisier avoids any reference to atoms or to minutest particles of matter and proposes, instead, a reformed nomenclature for chemistry, in which the names of compound substances would reflect their elementary composition . In fact, he regards the decomposition of material bodies into the substances of which they are composed as the chief aim of chemistry. Ultimately, however, this proposed reform of the nomenclature of compound substances in terms of their elementary composition forces the question of what is to be regarded as an element . Lavoisier proposes to answer this question by restricting himself to what can be ascertained by strict empirical means. He explains that, [i]f by the name of element, we mean the simple and indivisible molecules that compose bodies, it is probable that we do not know them if, on the contrary, we attach to the name of element or principle of bodies the idea of the last point at which analysis arrives, all of the substances that we have not yet been able to decompose by any means are, for us, to be considered elements. ... 

There is no completely satisfactory and universally recognised scheme of nomenclature for phosphorus compounds. There are, in fact, many inconsistencies and often a given compound will have at least two alternative names which are widely used. The systematic naming of compounds of even moderate complexity can often be very cumbersome and occasionally misleading. Some examples of alternative names for relatively simple compounds are given in Table 1.4. 

In Section 1, we introduced the use of Roman numerals to denote ionic charges in the Stock system of naming ionic compounds. The Stock system is actually based on oxidation numbers, and it can be used as an alternative to the prefix system for naming binary molecular compounds. In the prefix system, for example, SO2 and SO3 are named sulfur dioxide and sulfur trioxide, respectively. Their names according to the Stock system are sulfur(IV) oxide and sulfur(VI) oxide. The international body that governs nomenclature has endorsed the Stock system, which is more practical for complicated compounds. Prefix-based names and Stock-system names are still used interchangeably for many simple compounds, however. 

The nomenclature of coordination compounds is introduced in two sections. Here we consider the basics of naming ligands (including multidentate, ambidentate, and bridging) that occur in simple neutral as well as ionic coordination compounds. In Chapter 3, we will concentrate on the nomenclature for compounds for which a variety of isomers are possible. 

The nomenclature of compounds containing complex ions is more involved than that of the simple inorganic compounds considered in earlier chapters. We will see first how complex ions are named and then look at the nomenclature of coordination compounds. 

Synthesis by oxidation remains the first choice for commercial and laboratory preparation of quinones the starting material (1) provided the generic name quinone. This simple, descriptive nomenclature has been abandoned by Chemicaly hstracts, but remains widely used (2). The systematic name for (2) is 2,5-cyclohexadiene-l,4-dione. Several examples of quinone synonyms are given in Table 1. Common names are used in this article. 1,2-Benzoquinone (3,5-cydohexadiene-l,2-dione) (3) is also prepared by oxidation, often with freshly prepared silver oxide (3). Compounds related to (3) must be prepared using mild conditions because of their great sensitivity to both electrophiles and nucleophiles (4,5). 

When applying this principle to replacement names generated from fusion nomenclature, it is essential to keep in mind that fusion names for hydrocarbons ending in -cycloalkene are for fully unsaturated skeletons the -ene ending implies whatever number of double bonds may be necessary, without a multiplier. Thus (117) has six double bonds in the twelve-membered ring, and one must add ten hydrogens to saturate it to the stage of a simple benzene derivative, compound (118). 

Generally the name of a compound should correspond to the most stable tautomer (76AHCS1, p. 5). This is often problematic when several tautomers have similar stabilities, but is a simple and reasonable rule whose violation could lead to naming phenol as cyclohexadienone. Different types of tautomerism use different types of nomenclature. For instance, in the case of annular tautomers both are named, e.g., 4(5)-methylimidazole, while for functional tautomerism, usually the name of an individual tautomer is used because to name all would be cumbersome. In the case of crystal structures, the name should reflect the tautomer actually found therefore, 3-nitropyrazole should be named as such (97JPOC637) and not as 3(5)-nitropyrazole. 

Many compounds were given informal, common names before their compositions were known. Common names include water, salt, sugar, ammonia, and quartz. A systematic name, on the other hand, reveals which dements are present and, in some cases, the arrangement of atoms. The systemic naming of compounds, which is called chemical nomenclature, follows the simple rules described in this section. 

The aim of chemical nomenclature is to be simple but unambiguous. Ionic and molecular compounds use different procedures so it is important first to identify the type of compound. To name an ionic compound, we name the ions present and then combine the names of the ions. 

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