Isomers classification, 291 table

Miscellaneous Agents. Those chemotherapeutic agents, which do not fit into any of the classifications discussed, ate Hsted iu Table 7. Mitotane (67), a stmctural isomer of DDT, is used to iaduce chemical adrenalectomies iu patients having adrenal cancer by teduciug host levels of adrenocorticosteroids. 

The data from all of these spectra are compared in Table II, which lists the quadrupole splitting and the isomer shift (relative to iron in palladium) in millimeters per second and the ferric-ferrous ratio (as obtained from the Mossbauer data, by comparing the areas of the two sets of lines). The variations in the quadrupole splitting, ranging from 1.84 to 2.08 mm./sec., are certainly outside the range of experimental error and must be attributed to actual variations in the different tektites studied. The only type of tektite for which we measured many diflFerent samples was the indochinite, and the quadrupole splitting and isomer shift of these samples were the same for all samples within experimental error. Hence, these two parameters would be useful in verifying the classification of different types of tektites. The difficulties involved in... 

This classification, defined in Table 13 with examples, appears very clear and logical in view of the standard classification of isomers. However, the historical development followed a rather curious course. The term constitutional selectivity, unfortunately a somewhat clumsy word which is rarely used, appeared in the literature as late as 1979 -2. This was after an inspiring, but not completely clear, discourse by Hassner on the almost equivalent term regioselectivity which greatly appealed to chemists and was immediately accepted. It is important to note that the now universally accepted definition of stereoselectivity and its subclasses enantio- and diastercoselectivity did not appear in print until as late as 19714. Before that, the term stereoselectivity apparently had the special meaning of the present term diastereoselectivity5. One consequence of this was discussed in the previous section. Furthermore, in the past, the terms selectivity and specificity were usually coupled. The latter term will be discussed in Section 1.2.3.3, but it is currently regarded with suspicion and best avoided. 

Benzenoid (chemical) isomers are, in a strict sense, the benzenoid systems compatible with a formula C H, = (n s). The cardinality of C HS, viz. C HS = n, s is the number of isomers pertaining to the particular formula. The generation of benzenoid isomers (aufbau) is treated and some fundamental principles are formulated in this connection. Several propositions are proved for special classes of benzenoids defined in relation to the place of their formulas in the Dias periodic table (for benzenoid hydrocarbons). Constant-isomer series for benzenoids are treated in particular. They are represented by certain C HS formulas for which n s = In Sjl = n2 52 =. .., where (nk sk) pertains to the k times circumscribed C HS isomers. General formulations for the constant-isomer series are reported in two schemes referred to as the Harary-Harborth picture and the Balaban picture. It is demonstrated how the cardinality n s for a constant-isomer series can be split into two parts, and explicit mathematical formulas are given for one of these parts. Computational results are reported for many benzenoid isomers, especially for the constant-isomer series, both collected from literature and original supplements. Most of the new results account for the classifications according to the symmetry groups of the benzenoids and their A values (color excess). 

Their data [17], which correspond to the area to the left of the staircase-line in Fig. 2, cover all benzenoids with ne < 46. All these data, linked explicitly to the appropriate C HS formulas, are quoted in a previous review [20]. Most of them, for which the classification into Kekuleans and non-Kekuleans are known, are found in our main reference [8]. A supplement of unclassified numbers is given in Table 1. Out of these numbers those for odd-carbon atom formulas give, nevertheless, the numbers of non-Kekulean benzenoid isomers (equal to the totals) hence the corresponding positions are marked with asterisks in Fig. 2 this is not the case for the even-carbon atom formulas. 

Solubility. According to our classification system, all intra-molecular bonded materials should be Class AB. Consequently, they should be soluble in solvents from Classes AB, B, and A, provided the solvent can successfully compete with the internal H bonding. Because of the internal satisfaction of the H bonding tendency. Class N solvents should be better solvents for internally H bonded materials than for nonchelated compounds. This is the behavior observed, as shown in Table 5-V for dihydroxybenzenes in CCh. In the stronger acid and base solvents, the loss of chelation is suggested. Further, for this case, the table shows a similarity in the solubilities of ortho and meta isomers. 

For purposes of classification, 4-hydroxy-, 4-mercapto- and 4-amino-3-pyrazo in-5-ones, except 4-amino having no hydrogen on the nitrogen, have been considered to be 3,4-pyrazolidinediones or derivatives thereof. These compounds could theoretically exist as the 4-oxo, 4-thiono or 4-imino forms but do exist largely, if not exclusively, as the hydroxy, mercapto and amino isomers. The amino compounds will be named as 4-amino-3-pyrazolin-5-ones. They are listed in Table XLIV. 

The chemical composition of fuel oil is extremely complex, and an extremely high number of compounds can be present through the hydrocarbon types, the range of isomeric hydrocarbons (Table 9.2), and the various types and isomers of heteroatom constituents. Therefore, it is not practical to perform individual compound analyses but it is often helpful to define the compounds present under broad classifications, such as aromatics, paraffins, naphthenes, and olefins. 

Jerry Dias, a chemist at the University of Missouri—Kansas City, has devised a periodic classification of a class of organic molecules called benzenoid aromatic hydrocarbons, of which naphthalene, Cj Hg, is the simplest example (figure 1.10). By analogy with Johann Dobereiner s triads of elements, described in chapter 2, these molecules can be sorted into groups of three in which the central molecule has a total number of carbon and hydrogen atoms that is the mean of the flanking entries, both downward and across the table. This periodic scheme has been apphed to making a systematic study of the properties of benzenoid aromatic hydrocarbons, which has led to the predictions of the stabihty and reactivity of many of their isomers. 

Table 2 shows the numbers of single coronoid isomers according to the neo classification (n normal e essentially disconnected o non—Kekulean). Furthermore, the non—Kekulean systems, o, are classified according to their color excess (A). The table is arranged in a way which was found suitable for benzenoid isomers (Brunvoll, Cyvin BN and Cyvin 1992b). All the numbers in this table, although they have not been given before explicitly, can be deduced firom the data of Volume I, Tables 1-9.1 to 1-9.8. 

The actual forms of a number of single coronoid isomers are shown in Fig. 2. All these forms for < 14 are found to be consistent with the relevant numbers and classifications of Table 2 and of Table 4. The depictions go somewhat beyond h = 14. All the depicted forms for h> IS are extremal coronoids. 

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