Priorities prefixes

Functional Group Suffix if higher priority Prefix if lower priority Example when the functional group has lower priority ... 

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. 

Acyl Halides. Acyl halides, in which the hydroxyl portion of a carboxyl group is replaced by a halogen, are named by placing the name of the corresponding halide after that of the acyl radical. When another group is present that has priority for citation as principal group or when the acyl halide is attached to a side chain, the prefix haloformyl- is used as, for example, in fiuoro-formyl-. 

An aldehyde group is denoted by the prefix formyl- when it is attached to a nitrogen atom in a ring system or when a group having priority for citation as principal group is present and part of a cyclic system. 

Hydroxylamines and Oximes. For RNH—OH compounds, prefix the name of the radical R to hydroxylamine. If another substituent has priority as principal group, attach the prefix... 

Compounds of the type R NH—OR are named (1) as alkoxyamino derivatives of compound R H, (2) as A, 0-substituted hydroxylamines, (3) as alkoxyamines (even if R is hydrogen), or (4) by the prefix aminooxy- when another substituent has priority for parent name. Examples of each type are... 

When another group having higher priority for citation as principal group is also present, the ketonic oxygen may be expressed by the prefix 0x0-, or one can use the name of the carbonyl-containing radical, as, for example, acyl radicals and oxo-substituted radicals. Examples are... 

Trivial acid names are formed by changing the endings -oic acid or -ic acid to -onitrile. For example, CH3CN is acetonitrile. When the —CN group is not the highest priority group, the —CN group is denoted by the prefix cyano-. 

In order of decreasing priority for citation of a functional class name, and the prefix for substitutive nomenclature, are the following related compounds ... 

Peroxides. Compounds of the type R—O—OH are named (1) by placing the name of the radical R before the word hydroperoxide or (2) by use of the prefix hydroperoxy- when another parent name has higher priority. For example, C2H5OOH is ethyl hydroperoxide. 

Ester groups in R —CO—OR compounds are named (1) by the prefix alkoxycarbonyl- or aryloxycarbonyl- for —CO—OR when the radical R contains a substituent with priority for citation as principal group or (2) by the prefix acyloxy- for R —CO—O— when the radical R contains a substituent with priority for citation as principal group. Examples are... 

For nomenclature purposes, substituents can be divided into those that are always cited as prefixes (e.g. chloro-, alkoxy-) and those which can be cited as either prefixes or suffixes e.g. oxo-/-one, carbamoyl-/-carboxamide). If any of the latter are present, the name will normally contain a suffix. However, only one kind of group can be cited as suffix, and this is chosen according to a strict order of priorities. The group thus selected is known as the principal characteristic group . 

Table 7 lists some of the commonest substituent groups and the corresponding prefixes and/or suffixes, in order of priority for selection as principal group. Some examples of their use are given in (148)-(152). 

The numbering of monocyclic hydrocarbons is not fixed, as any carbon atom may receive the locant 1 . Non-detachable prefixes have priority for lowest locants, and if this is indicated hydrogen it must receive the locant 1 . The importance of the presence of an indicated hydrogen is evident in substituted rings. 

In molecules with functional groups, such as —COOH, that have a higher naming priority, the carbonyl group is indicated by the prefix keto-. Thus, CHj—CO—CHj—CHj—COOH is 4-ketopentanoic acid. Groups like... 

In certain polyfunctional compounds, an aldehyde or ketone group can also be named as a substituent on a molecule with another functional group as its root. The aldehyde carbonyl is given the prefix formyl-, and the ketone group is named 0x0- with a number to show its position in the molecule. Compounds with both an aldehyde and ketone are named as aldehydes, because aldehydes have functional group priority over ketones. A ketone containing a benzene ring is named as a -phenone. 

Examples of Replacement Prefixes (in Descending Order of Priority)"... 

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