有机化合物的英文命名

NOMENCLATURE OF ORGANIC COMPOUNDS

A complete discussion of definitive rules of organic nomenclature would require more space than can be allotted in this text. We will survey some of the more common nomenclature rules, both IUPAC and trivial.

Alkanes

The names for the first twenty continuous-chain alkanes are listed in Table 1.

Table 1 Names of continuous-chain alkanes

Alkenes and Alkynes

Unbranched hydrocarbons having one double bond are named in the IUPAC system by replacing the ending -ane of the alkane name with -ene. If there are two or more double bonds, the ending is -adiene, -atriene, etc.

Unbranched hydrocarbons having one triple bond are named by replacing the ending -ane of the alkane name with -yne. If there are two or more triple bonds, the ending is -adiyne, -atriyne etc. Table 2 shows names for some alkyl groups, alkanes, alkenes and alkynes.

Table 2 Some Alkanes, Alkyl, Alkenes, Alkynes

The Prefixes

In the IUPAC system, alkyl and aryl substituents and many functional groups are named as prefixes on the parent (for example, iodomethane). Some common functional groups named as prefixes are listed in Table 3.

Table 3 Some Functional Groups Named as Prefixes

In simple compounds, the prefixes di-, tri-, tetra-, penta-, hexa-, etc. are used to indicate the number of times a substituent is found in the structure: e.g., dimethylamine for (CH3)2NH or dichloromethane for CH2Cl2.

In complex structures, the prefixes bis-, tris-, and tetrakis- are used: bis- means two of a kind; tris-, three of a kind; and tetrakis-, four of a kind. [(CH3)2N]2 is bis(dimethylamino) and not di(dimethylamino).

Nomenclature Priority of Functional Groups

In naming a compound, the longest chain containing principal functional group is considered the parent. The parent is numbered from the principal functional group to the other end, the direction being chosen to give the lowest numbers to the substituents. The entire name of the structure is then composed of (1) the numbers of the positions of the substituts (and of the principal functional group, if necessary); (2) the names of the substituts; (3) the name of the parent.

The various functional groups are ranked in priority as to which receives the suffix name and the lowest position number1. A list of these priorities is given in Table 4.

Ketones

In the systematic names for ketones, the -e of the parent alkane name is dropped and -one is added. A prefix number is used if necessary.

In a complex structure, a ketone group my be named in IUPAC system with the prefix oxo-. (The prefix keto- is also sometimes encountered.)

Table 4 Nomenclature Priority*

Alcohols

The names of alcohols may be: (1) IUPAC; (2) trivial; or, occasionally, (3) conjunctive. IUPAC names are taken from the name of the alkane with the final -e changed to -ol. In the case of polyols, the prefix di-, tri- etc. is placed just before -ol, with the position numbers placed at the start of the name, if possible, such as, 1,4-cyclohexandiol. Names for some alkyl halides, ketones and alcohols are listed in Table 5.

Table 5 Some Alkyl halides, Ketones and Alcohols