Locants substitution

No locants are needed m the absence of substituents it is understood that the double bond connects C 1 and C 2 Substituted cycloalkenes are numbered beginning with the double bond proceeding through it and continuing m sequence around the ring The direction is chosen so as to give the lower of two possible numbers to the substituent... 

Diols are almost always given substitutive lUPAC names As the name of the prod uct m the example indicates the substitutive nomenclature of diols is similar to that of alcohols The suffix dwl replaces ol and two locants one for each hydroxyl group are required Note that the final e of the parent alkane name is retained when the suffix begins with a consonant ( diol) but dropped when the suffix begins with a vowel ( ol)... 

Section 17 1 The substitutive lUPAC names of aldehydes and ketones are developed by identifying the longest continuous chain that contains the carbonyl group and replacing the final e of the corresponding alkane by al for aldehydes and one for ketones The chain is numbered m the direction that gives the lowest locant to the carbon of the carbonyl group... 

Secondary and tertiary amines are named as N substituted derivatives of primary amines The parent primary amine is taken to be the one with the longest carbon chain The prefix N is added as a locant to identify substituents on the ammo nitrogen as needed... 

When the parent molecules connected by the azo group are different, azo is placed between the complete names of the parent molecules, substituted or unsubstituted. Locants are placed between the affix azo and the names of the molecules to which each refers. Preference is given to the more complex parent molecule for citation as the first component, e.g., 2-aminonaphthalene-l-azo-(4 -chloro-2 -methy Ibenzene). 

For oximes, the word oxime is placed after the name of the aldehyde or ketone. If the carbonyl group is not the principal group, use the prefix hydroxyimino-. Compounds with the group Z = N—OR are named by a prefix alkyloxyimino- as oxime O-ethers or as O-substituted oximes. Compounds with the group r C=N(0)R are named by adding A-oxide after the name of the alkylideneaminc compound. For amine oxides, add the word oxide after the name of the base, with locants. For example, C5H5N—O is named pyridine A-oxide or pyridine 1-oxide. 

Lactones, l xictides, iMciams, and Lactims. When the hydroxy acid from which water may be considered to have been eliminated has a trivial name, the lactone is designated by substituting -olactone for -ic acid. Locants for a carbonyl group are numbered as low as possible, even before that of a hydroxyl group. 

Alkylamines are nfflned in two ways. One method adds the ending -amine to the nfflne of the alkyl group. The other applies the principles of substitutive nomenclature by replacing the -e ending of an alkane name by -amine and uses appropr iate locants to identify the position of the fflnino group. Arylfflnines are nfflned as derivatives of aniline. 

Rules for designating isotopic substitution and labelling are given in [13] (Section H). Parentheses indicate substitution square brackets indicate labelling. The locant U indicates uniform labelling. 

Note. C-Locants are essential only where there is potential ambiguity, to make clear whether substitution is at carbon or at a heteroatom (cf. 2-Carb-16) however, they may also be used for emphasis. 

Substituents replacing the hydrogen atom of an alcoholic hydroxy group of a saccharide or saccharide derivative are denoted as O-substituents. The 0- locant is not repeated for multiple replacements by the same atom or group. Number locants are used as necessary to specify the positions of substituents they are not required for compounds fully substituted by identical groups. Alternative periphrase names for esters, ethers, etc. may be useful for indexing purposes. For cyclic acetals see 2-Carb-28. 

Note. In carbohydrate nomenclature, substitution at a heteroatom is normally indicated by citing the locant of the attached carbon atom, followed by a hyphen, and then the italicized heteroatom element symbol, e.g. 2-0-methyl, 5-N-acetyl. Substituents on the same kind of heteroatom are grouped (e.g. 2,3,4-tri-0-methy 1), and substituents of the same kind are cited in alphabetical order of heteroatoms (e.g. 5-N-acetyl-4,8,9-tri-0-acetyl). The alternative format with superscript numerical locants (e.g, N5,(/,(), ( -tetraacetyl), used in some other areas of natural product chemistry, is unusual in carbohydrate names. 

IUPAC substitutive nomenclature locants, prefixes, parent compound, and one suffix. 

Further choice in this case is based on the lowest locant for substitution, so that the preferred CRU is... 

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. 

For example, substitution can be made on an oxygen atom in the case of esters and ethers. It is characterised by the symbol O, which is placed after the locant. The compound prefix deoxy- is composed of the prefixes de-, meaning without in subtractive nomenclature, and oxy-, to indicate the subtraction of an oxy group from an -OH group C-O-H C-H. Such an operation is needed when an -OH group is replaced by another group, such as an amino group. 

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. 

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