Order of prefixes

As follows from the preceding chapters, prefixes of the most diverse meaning play an often decisive role in the systematization of compound names. It is therefore necessary to regulate more or less strictly the ordering of these prefixes in constructing a systematic name. 

All prefixes encoding explicit statements about the structure of a pertinent acyclic or cyclic parent system are incorporated into the stem terms, i. e. treated as non-detachable parts of a name. 

In contrast, all substitutive prefixes (Tables 6,8) are treated as detachable and ordered alphabetically. 

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Order of prefixes. When the substituents have been identified, the main chain has been numbered, and the proper multipliers such as di- and tri- have been assigned, the name is written with the substituents listed in alphabetical,... 

Rule 4. Name the side chains by approved radical names and precede these with the correct position numbers. For the acyclics, the complexity order and the alphabetical order of prefixes will be identical, since only methyl and methylene side chains are involved — for example, 2,6-dimethyl in geraniolene (Nos. 1A and IB, Chart 3) and 7-methyl-3-methylene in myrcene (No. 2, Chart 3). 

Numbers within the Rings Indicate the Systematic Numbering Based on Chemical Abstracts Order of Prefixes Numbers outside the Rings Indicate the Usual Terpene Numbering. These Numberings Are Those in Current Usage and Are Not Necessarily the Recommended Numberings. 

No. Common Terpene Name Systematic Name — Chemical Abstracts Order of Prefixes Low Numbers to Double Bonds and Substituents Recommended Name Fixed Numbering... 

See Chart 6 for the structures and recommended names. In these names, the Chemical Abstracts order of prefixes has been followed. Compounds Nos. 30-32 and 34-38 are those which up to now have usually been included in treatises on terpenes. Many of the other structures, however, surely warrant inclusion in the future. 

IUPAC Rule 64 (41) states "The expression lowest numbers signifies those that include the lowest individual number or numbers . Thus, 1,3 is lower than 2,4 1,1,3 lower than 1,3,3 1,5,5 lower than 2,2,6 1,2,3,5 lower than 1,3,4,5. At one time Chemical Abstracts interpreted "lowest numbers to mean those which yielded the lowest sum — for example, 2,2,6 (which adds up to 10) was considered lower numbering than 1,5,5 (which adds up to 11). Now, however, this practice has been abandoned, and the lowest individual numbers are the determining factor (10, 44). If two sets of lowest numbers for double bonds and substituents are equally possible according to IUPAC Rule 64, then the chosen order of prefixes — that is, alphabetical or complexity — becomes the determining factor. Examples of this numbering rule from formulas and names shown in Chart 6 are The substituents in No. 30 are at 1,5,5 and not at... 

Recommended Systematic Names Are Based on IUPAC Rules and Chemical Abstracts Order of Prefixes. Formulas Are Oriented So That No. 1 Carbon Is at Top, and the Numbering Runs Clockwise... 

British and American cooperation has reduced to some extent differences in practice in these two English-speaking countries. The British have adopted many of the CA practices, including alphabetic order of prefixes. One of the differences has been in the use of italicized prefixes. The British have italicized many more prefixes than have the Americans. This means a different placement of such names in indexes, since italicized prefixes are not considered in alphabetizing. American and British cooperation has been extended and some of these differences have been eliminated. Thus the British no longer italicize bicyclo-, cyclo-, epi-, iso-, seco-, and spiro- (17). 

The British have adopted, from American practice, the alphabetical order of prefixes have reconsidered part of the organophosphorus nomenclature in order to open the way to agreement in that field and will make the many changes demanded by the 1949 IUPAC organic rules when these reach final form. 

The type of heteroatom is indicated by a prefix according to Table 1. The sequence in this table also indicates the preferred order of prefixes (principle of decreasing priority). 

It is important to note that multiplying prefixes have no influence on the alphabetical order of prefixes. The names of substituted substituents are alphabetized as a whole otherwise such substituent groups are subject to the same rules as are applied to parent structures, with two exceptions a) even high-ranked characteristic groups are expressed as suffixes here and b) the linking position (free valence) has the lowest possible locant within the limitations put forth in Section 6.4. For chain substituents this is traditionally always locant 1. 

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