Locants capitalization

When side chains of two or more different kinds are attached to a cyclic component, only the senior side chain is named by the conjunctive method. The remaining side chains are named as prefixes. Likewise, when there is a choice of cyclic component, the senior is chosen. Benzene derivatives may be named by the conjunctive method only when two or more identical side chains are present. Trivial names for oxo carboxylic acids may be used for the acyclic component. If the cyclic and acyclic components are joined by a double bond, the locants of this bond are placed as superscripts to a Greek capital delta that is inserted between the two names. The locant for the cyclic component precedes that for the acyclic component, e.g., indene-A - -acetic acid. 

Radicals from partially hydrogenated heterocycles may be named in two ways in the usual manner, using the appropriate hydro prefix for the parent compound, or by use of the indicated hydrogen convention (italic capital H and locant, enclosed in parentheses). The symbol for the indicated hydrogen must be written immediately following the locant for the radical site, e.g. (163). 

When a name applies equally to two or more isomeric condensed parent ring systems with the maximum number of non-cumulative double bonds and when the name can be made specific by indicating the position of one or more hydrogen atoms in the structure, this is accomplished by modifying the name with a locant, followed by italic capital H for each of these hydrogen atoms. Such symbols ordinarily precede the name. The said atom or atoms are called indicated hydrogen . The same principle is applied to radicals and compounds derived from these systems. 

As exceptions, Greek capital delta (A), followed by superscript locant(s), is used to denote a double bond in a compound named according to Rule B-l.2 if its name is preceded by locants for hetero atoms and also to denote a double bond uniting components in an assembly of rings (cf. Examples to Rules A-52.1 and C-71.1) or in conjunctive names (cf. Rule C-55.1). 

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. 

In some cases, heterocyclic systems occur as one or more structural isomers which differ only in the position of an H-atom. These isomers are designated by indicating the number corresponding to the position of the hydrogen atom in front of the name, followed by an italic capital H. Such a prominent H-atom is called an indicated hydrogen and must be assigned the lowest possible locant. 

In long sequences, as in transfer RNA s, where it is preferable to have not more than one capital letter per nucleoside residue, the standard symbols for nucleosides [i.e.. A, U, G, C, etc. (see N-3.2.1)] may be modified by a symbol of lower case letter(s) placed immediately before the single capital letter. Those symbols recommended for more common modifications are listM below (for locants and multipliers, see N-4.4 for unusual sugar residues, see N-3.2.2 and N-3.2.3 ... 

In presenting several homologous sequences, it is often desired to keep the capital letters representing nucleotides one below another. The presence of modif3dng symbols may interfere with such a presentation. One way of meeting this situation is to place the prefixes (includ g locants and multipliers) directly over the capital letter they modify, and to place the suffix (usually m for 2 -0-methyl) as a right-hand... 

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