Locants functional groups

Multiple anions are named by using the suffixes -diide , -triide , etc., with such locants as may be necessary, and without eliding terminal e . No other suffixes denoting functional groups may be used with -ide endings functional groups must be indicated by prefixes, as in (194)-(200). 

A chemical name typically has four parts in the IUPAC system of nomenclature prefix, locant, parent, and suffix. The prefix specifies the location and identity of various substituent groups in the molecule, the locant gives the location of the primary functional group, the parent selects a main part of the molecule and tells how many carbon atoms are in that part, and the suffix identifies the primary functional group. 

The most senior of other functional groups expressed in the suffix receives the lowest possible locant, i.e. carboxylic acid (derivatives) > (potential) ketonic carbonyl groups. 

With larger molecular structures, neither system reveals immediately that fluorine has taken the place of all hydrogen atoms attached to carbon atoms except those whose substitution would affect the nature of the functional group present. This is exactly what the lUPAC-ap-proved term perfluoro denotes, and its wide usage since 1952 attests to its value. In addition to providing instant recognition of compound type, its use makes names less cumbersome, since fluorine locants are completely unnecessary. 

It is normal British practice to place the numeral referring to the position of a molecular feature (i.e., its locant) immediately before the syllable it qualifies. American usage is more variable (although the same procedure is followed in cases where confusion or ambiguity might result) it is common to find the locant for a multiple bond or for the principal functional group at the beginning of the name (or immediately... 

To name alkenes, we follow the basic IUPAC rules, but add the suffix -ene to indicate the main functional group is an alkene. The location of the double bond is given by a locant number, which identifies the first carbon in the double bond. The main functional group always gets the lowest number. Figure 11.9 illustrates some example alkene structures and names. 

Number the atoms on this chain beginning at the end near the first branch point, so the lowest locant numbers are used. Number functional groups from the attachment point. 

The preferred parent is that which contains the lowest locants for functional groups. 

Many simple common compounds are known by both a trivial and a systematic name. The systematic names are helpful in learning the structures of organic compounds, but the trivial names are often simpler and can reflect the source or dominant reactivity of the compound concerned. The systematic name for a compound has a stem that describes the carbon skeleton, prefixes and suffixes that indicate the functional groups, and numbers (locants) that define their position. Prefixes may also be added to indicate modifications to the carbon skeleton and to define the stereochemistry. A list of the more common prefixes, suffixes and stems is given in Table 1.2. 

The locant for a suffix (whether it is for an alcohol or another functional group) may be placed before the parent name as in the above example or, according to a 1993 lUPAC revision of the rules, immediately before the suffix. Both methods are lUPAC approved. Therefore, the above compound could also be named 4-methylhexan-1-ol. 

Locant (Section 3.4) A number in a chemical name that locates the positions of the functional groups and substituents in the molecule. 

Completing the structural description is a secondary portion of the name that is really in two parts. One part describes the methyl substitution at position 3 of the hve-carbon chain. The other part describes the substitution at position 5. This latter portion is a cyclohexene ring that is itself substituted as indicated by the level of parentheses that offset it from the locant, 5 . Note that the alcohol functional group is termed hydroxy while the ketone functional group is termed oxo . 

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