Phosphorus compounds nomenclature

The first seven-coordinate phosphorus compound, 12, containing a spiro phosphorus atom has recently been reported <2000IC1338>. The IUPAC recommendations for the nomenclature of spiro compounds was revised and extended in 1999 <1999PAC531>. 

The nomenclature used for phosphorus chalcogen containing molecules is often inconsistent in the literature, with several different naming schemes in current use. Hence for clarity, the naming system employed for the main chalcogen-phosphorus compounds in this chapter is detailed in Figure 1. 

Quite often, we find nonsystematic nomenclature used in the literature dealing with organophosphorus compounds. This results in unnecessary confusion, as systematic nomenclature is easy to use and understand. Nomenclature based on the oxidation state of the phosphorus center eliminates the confusion and helps to promote understanding of the chemistry as well as to facilitate communication. Table 1.1 shows structures for tricoordinate and tetracoordinate phosphorus compounds related to oxyacids with their English general names. Also noted are the names for simple esters of the parent acids. They are organized based on oxidation state and the number of bonds of the carbon-phosphorus type. 

It will be seen that the above system of nomenclature has the virtue of simplicity and is easy to memorize. All that one has to keep in mind is phosphon- for quinquivalent phosphorus compounds and phosphin- for tervalent phosphorus compounds. In fact, the above system was successfully used in Britain until 1950 and may be summarized thus ... 

Another system, which is also allowed by IUPAC and is sometimes very convenient (but which should be avoided when official names are established by IUPAC and cited in Chemical Abstracts), is the so-called a -nomenclature, in which the term phospha indicates replacement of carbon by phosphorus, e.g. phosphacyclohexane = phosphorinane, and phosphabenzene = A3- phosphorin. Five-coordinate phosphorus compounds are called phos-phoranes. However, this name is also used for phosphorus ylides with a four-coordinate phosphorus and a more or less polar R3f—CX moiety or a d -p R3P=CX double bond, e.g. methylenetriphenylphosphorane = triphenylphosphorus methylene ylide or tri-phenylphosphonium methyl ylide, Ph3P=CH2 = Ph3P—CH2. 

Unfortunately the name phosphorane according to IUPAC (and Chemical Abstracts) nomenclature is not restricted to phosphorus compounds with five covalent bonded ligands,... 

Phosphorus compounds, of nitrogen, nomenclature of, 2 285 Phosphorus (I II) cyanide, 6 84... 

Similarly, phosphorus occurs directly beneath nitrogen in the periodic table and therefore often exhibits a valence of three. Again, structures with an expanded valence, having five bonds to the phosphorus, are common, especially when the extra bonds are to oxygen. This book is not concerned with all the possible sulfur and phosphorus compounds, nor does it spend much time on their nomenclature. Instead, it concentrates on those of most importance in organic chemistry and biochemistry. Let s begin with a discussion of some common sulfur compounds. 

For nomenclatural classification, a pentacoordinated phosphorus compound, P(L],L2,L3,L4,L5), with five different ligands, Lx. . . L5, attached to a skeleton of five positions identified by the indices s =1... 5, and of trigonal bipyramidal symmetry, D3h, can exist as 5 /6=20 isomers, or 10 pairs of enantiomers. To represent these isomers one defines a Reference Molecule ME in which the indices of all the ligands and the indices of all the skeletal positions coincide. Those indices will not coincide in the isomers of ME. The skeletal indices are assigned to the Reference Molecule according to some definitions,65 for example, as shown in ME. The ligand indices are assigned to the Reference Molecule... 

A few years ago the workers interested in phosphorus compounds felt the need of imiform nomenclature, at least among English-speaking chemists. They foimd what seemed an insurmoimtable obstacle in the different approaches used in naming these compounds. Finally a compromise solution was offered and it was agreed to work on that basis. The rules so far have been limited to monophosphorus compoimds (2). 

These names are very useful for indexes. The names are in use in British literature and will be used more and more in the ACS journals. European chemists have diflBculty in converting the names into their languages, and have made some counter proposals. It will take time to solve all the problems in the nomenclature of phosphorus compounds, especially for polyphosphorus compounds. 

The problems of nomenclature of arsenic compounds and the confusion connected with them, mainly a result of incorrect translations, are comparable to the situation in phosphorus chemistry. In principle, the nomenclature of arsenic compounds is similar to that of phosphorus compounds. 

This form of nomenclature attempts to relate the structure to that of an analogous carbohydrate, and has been widely adopted by those working in the area. Nevertheless, it is not consistent with the customary manner of naming heterocyclic phosphorus compounds. A more systematic way of naming the substance would be either l,3,4,5-tetrahydroxy-l-oxo-2-phospholanemethanol or 1-hydroxy-2-hydroxymethyl-3,4,5-phospholanetriol 1 -oxide. 

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. 

Phosphorus heterocyclic compounds, 1, 493-538 five-membered ring systems, 1, 513-523 nomenclature, 1, 496 six-membered ring systems, 1, 497-513 Photoaromatization oxirenes from, 7, 125-126 Photobleaching chromenes in, 3, 880 Photochemical reactions heterocyclic compound synthesis from, 5, 159 reviews, 1, 56 heterocyclic compounds reviews, 1, 71, 72... 

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