Nomenclature indicated hydrogen

Hsynthesis from, 3, 767 Indenobenzazepines pharmacological properties, 7, 546 Indenone oxide, 2,3-diphenyl-photochromic compound, 1, 385 In deno[ 1,2-c][ 1,2,4]triazines synthesis, 3, 434 Indicated hydrogen nomenclature, 1, 33 Indigo, I, 317, 318-319, 4, 370 Baeyer synthesis, 1, 319 colour and constitution, 1, 344-345 molecular structure, 4, 162 photochromic compound, 1, 386 synthesis, 4, 247 Indigoid dyes... 

Indicated hydrogen in aromatic systems is assigned to angular or non-angular positions when needed to accommodate structural features in systematic nomenclature. The lowest locants are used. 

The resonance structures of the 2-substituted pyrazole 1-oxides 74 are discussed in Section 1.1.1. According to IUPAC nomenclature, structure 86 is a 1-substituted lH-pyrazole 2-oxide since the rules dictate that when R=H the indicated hydrogen position takes numbering precedence. Other names found in the literature are 1-substituted pyrazole 2-oxides or 1-substituted 2-oxo-1 H-pyrazoles. Frequently the numbering is switched to give the names 2-substituted 2H-pyrazole 1-oxide, 2-substituted pyrazole... 

The nomenclature of compounds listed in this index follows the usage of the authors of the chapters and not necessarily the strict lUPAC or Chemical Abstracts style. However, when a chemical name as used by the authors is widely divergent from accepted usage, the more appropriate name has been marked with an asterisk to alert the user that the index entry may not appear in the text on the page indicated. To keep entries brief, "obvious" details, such as indicated hydrogen in its usual or only possible place, have been omitted. 

This method of locating bridging hydrogen atoms is adapted from the indicated hydrogen method in organic nomenclature (see Section P-14.6 of Ref. 1). The indicated hydrogen method would yield the name (2,3-p7U,(2,5-p//),(3,4-p77),(4,5-p/T)-M °-pentaborane(9). 

The nomenclature used in this chapter follows lUPAC rules as laid down in the lUPAC Nomenclature of Organic Compounds, 1979 edition. Thus the parent compounds and the dihydro-1,3-oxazines have the names indicated in Figure 1, where the locant for H (the indicated hydrogen) is always given the lowest number. 

In substitutive nomenclature the use of the prefix oxo- or the suffix -one means the insertion of =0 in place of two hydrogen atoms. This is straightforward when the parent carries a CHz group at the appropriate position (example 206), but often the insertion of =0 requires prior reduction of a double bond. When the prefix oxo- is employed, this is achieved by using the appropriate hydro- prefix terms (example 207). However, the suffix -one can be used without hydro , the required reduction being implied rather than overtly stated (example 208) if desired the position of the hydrogen atom introduced to accommodate the carbonyl can be indicated in parentheses (see also examples 123 and 124). 

In Figure 4.2 we have drawn how we can distinguish the two faces of an alkene, or rather the side of attack of a specific atom of the alkene. The arrow on the left approaches the lower carbon of the alkene and when looking from this viewpoint we count the weight of the three substituents the same way as in the CIP rules. We then see the order 1, 2, and 3 counter-clockwise, and we say that the arrow approaches the carbon atom from the si face. For simplicity we call this the si face of the alkene and in most cases this will do. If all four substituents at the alkene are different we can determine the re/si properties of both carbon atoms and these may be different This results in the nomenclature that an alkene may have a re,re and si,si face or re,si and si,re face. Thus, in the latter case one has to indicate to which atom the label is referring. For any enantiospecific, catalytic reaction (hydrogenation, hydroformylation, polymerisation) it is very convenient to use the re and si indicators in the discussion. 

Hydrogenation products of complex aromatic ring systems that are not treated as alicyclic hydrocarbons are named by prefixing dihydro, tetrahydro, etc., to the parent name. The lowest locants are used. Perhydro" is used in trivial nomenclature to indicate a fully hydrogenated compound. 

Organic adsorbates pose a particular problem because quite particular structures of some complexity are regularly discussed. A nomenclature is recommended in which the surface is treated as a substituent which replaces one or more hydrogen atoms. The degree of substitution is indicated by monoadsorbed, diadsorbed, etc. This terminology does not specify the nature of the chemical bonding to the surface nor does it restrict, a priori, the valency of the surface site. Thus, both of the following species... 

The hypothesis was discussed by K. Auwers and V. Meyer, H. Goldschmidt, E. Muller, A. Hantzsch, E. Beckmann, etc. In order to distinguish between these isomeric forms of, say, the benzaldoxim.es, A. Hantzsch employs the term syn as a prefix to indicate that the hydroxyl group lies on the same side of the mol. as the hydrogen atom of the aldehyde, and anti when the hydrogen and hydroxyl lie on opposite sides of the mol. The same nomenclature is applied to other compounds, e.g. the potassium benzoylphenyldiazotates, etc. Thus ... 

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