Locants letters

If the same alkyl group occurs more than once as a side chain, this is indicated by the prefixes di-, tri-, tetra-, etc. Side chains are cited in alphabetical order (before insertion of any multiplying prefix). The name of a complex radical (side chain) is considered to begin with the first letter of its complete name. Where names of complex radicals are composed of identical words, priority for citation is given to that radical which contains the lowest-numbered locant at the first cited point of difference in the radical. If two or more side chains are in equivalent positions, the one to be assigned the lowest-numbered locant is that cited first in the name. The complete expression for the side chain may be enclosed in parentheses for clarity or the carbon atoms in side chains may be indicated by primed locants. 

Rule 3 Number the substituents according to their position on the chain, and write the name listing the substituents in alphabetical order and identifying the position to which the -OH is bonded. Note that in naming ns-l,4-cyclohexanediol, the final -e of cyclohexane is not deleted because the next letter, d. is not a vowel, that is, cyclohexanediol rather than cyclohexandiol. Also, as with alkenes (Section 6.3), newer IUPAC naming recommendations place the locant immediately before the suffix rather than before the parent. 

The variants are distinguished by the locants of those ring atoms that lie outside a reference plane (defined below) and are listed for some examples in Table 1. The locants of ring atoms that lie on the side of the reference plane from which numbering appears clockwise (i.e. the upper side in the normal Haworth representation of furanoses and pyranoses) are written as superscripts and precede the letter those that lie on the other side are written as subscripts and follow the letter. Heteroatoms (e.g. O, S) are indicated by their subscript or superscript atomic symbols. Table 1 gives the notations and Chart III some examples. 

Oligosaccharide and polysaccharide structures occur not only in free form but often as parts of glycopeptides or glycoproteins [11] or of glycolipids [21]. It can be cumbersome to designate their structures by using the recommendations of 2-Carb-37. The use of three-letter symbols for monosaccharide residues is therefore recommended. With appropriate locants and anomeric descriptors, long sequences can thus be adequately described in abbreviated form. 

In the condensed form, the configurational symbol and the letter denoting ring size are omitted. It is understood that the configuration is D (with the exception of fucose and iduronic acid which are usually L) and that the rings are in pyranose form unless otherwise specified. The anomeric descriptor is written in the parentheses with the locants. 

Locants, which may be letters or numerals, and may be prefixes, infixes or suffixes. 

When a system does not have a retained name or a name that can be composed systematically as above, and when ortho- and ortho-peri- x% on are possible, it is named using fusion nomenclature, i.e. by combining the names of the two or more systems that are fused. One system is adjudged to be the senior according to criteria described elsewhere and is taken as a parent hydride, and the other is denoted in the name by a non-detachable prefix. The junction of the two systems is indicated in a specific manner. Instead of numerical locants, italic letters a , 6 , c , etc. are used to identify bonds in the parent hydride. The final letter o and normal locants are characteristic of the prefix. The examples below illustrate the fusion operation and the resulting fusion name. 

A component fused to the base component (referred to as a primary component) is cited as a prefix terminating usually in o, with the locants of the bond engaged in fusion specified in square brackets in the order corresponding to the direction of lettering of the base component, as in example 13. A (secondary) component fused to a primary component is cited as a further prefix, with the use of primes to indicate the... 

Orf/io-fused and ortho- and pen-fused ring compounds containing hetero atoms are named according to the fusion principle described in Rule A-21 for hydrocarbons. The components are named according to Rules A-21, B-l and B-2. When the name of a component in a fusion name contains locants (numerals or letters) that do not apply also to the numbering of the fused system, these locants are placed in square brackets (as are also the locants for fusion positions required by Rule A-21.5). The base component should be a heterocyclic system. If there is a choice, the base component should be, by order of preference ... 

Do not capitalize chemical names or nonproprietary drug names unless they are at the beginning of a sentence or are in a title or heading. In such cases, capitalize the first letter of the English word, not the locant, stereoisomer descriptor, or positional prefix. (See Chapter 12, Names and Numbers for Chemical Compounds .)... 

The names of chemical compounds may consist of one or more words, and they may include locants, descriptors, and syllabic portions. Locants and descriptors can be numerals, element symbols, small capital letters, Greek letters, Latin letters, italic words and letters, and combinations of these. Treat the word or syllabic portions of chemical names just like other common nouns use roman type, keep them lowercase in text, capitalize them at the beginnings of sentences and in titles, and hyphenate them only when they do not fit completely on one line. 

Use commas between numeral locants, chemical element symbol locants, and Greek locants, with no space after the comma. When a single locant consists of a numeral and a Greek letter together with no space or punctuation, the numeral precedes the Greek letter. When the Greek letter precedes the numeral, they indicate two different locants and should be separated by a comma. For example, a,2 denotes two locants la is viewed as one locant. 

The prefixes /ac- and mer- (facial and meridianal) are accepted. Letters are to be used as locant designators around a center of coordination. Their use has been extended to (1) multidentate ligands (even branched ones), (2) all known configurations around a central atom, and (3) multinuclear entities (provided they are not branched). 

Since the benzene rings are located by letters in the name, only the locant numbers of the N (in square brackets since they do not refer to the total ring) are needed for the name. 

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