6.0 Nomenclature of compounds with functional groups named as suffixes

  General Organic Chemistry

    6.0 Nomenclature of compounds with functional groups named as suffixes

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6.0 Nomenclature of compounds with functional groups named as suffixes

General naming scheme

The name of every organic molecule containing a functional group whose name appears as a suffix may be thought of as made up of four parts.

The principal functional group (PFG) whose suffix name is arranged in the order of decreasing priority.

Class	Formula	Prefix	Suffix
Cation	$ - NR_3^ + $	ammonio-	-ammonium
Carboxylic acid	$-COOH$	carboxy-	-oic acid
Sulfonic acid	$-SO_2OH$	sulfo-	-sulfonic acid
Salt of carboxylic acid	$-COO^-\ M^+$	carboxylato-	cation name .. - oate
Ester	$-COOR$	R-oxycarbonyl-	R-...-oate
Acid halide		haloformyl-	-oyl halide
Amide		carbamoyl-	-amide
Nitrile		cyano-	-nitrile
Aldehyde		formyl-	-al
Ketone		oxo-	-one
Alcohol	$-OH$	hydroxy-	-ol
Thiol	$-SH$	mercapto	-thiol
Amine	$-NH_2$	amino-	-amine
Imine	$=NH$	imino-	-imine
Ether	$-OR$	R-oxy-	-
Thioether	$-SR$	R-thio-	-

Wherever $"R"$ appears in the prefix or suffix table, then the group name (i.e. alkyl, alkenyl etc) for the $R$ group is used.

A. Choosing the principal chain

The principal chain is chosen according to the following rules, applied in order:

(a). The chain must contain the (maximum number of) principal functional group(s)l then

(b). It must contain the maximum number of double and triple bonds, then

(c). It must be the longest possible carbon chain (the carbons of the $-CO_2H$. $ - C \equiv N$, $ - C\left( { = O} \right)H$ etc groups are counted when they form part of the principal chain).

(B). Naming the principal chain

The principal chain is named after the alkane having the same number of carbon atoms and is modified when unsaturated by the replacement of "ane" by "en(e)", "enyn(e)", "adiene", etc. The final "e" of the name is omitted before "y" or a vowel (e.g. methaneol becomes methanol).

(C). Numbering the principal chain

The principal chain is numbered according to the following rules, taken in order:

(a). The PFG's must be given the lowest possible numbers; then,

(b). The double and triple bonds must be given the lowest possible numbers; then,

(c). The remaining functional groups and substituents must be given the lowest possible numbers.

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The following example illustrates the basic approach to naming:

Principal group		-one
Principal chain		hexane
Principal chain + principal group		2-hexanone
Modified name ("ane" becomes "en")		3-hexen-2-one
Prefixes (alphabetical with location number)	$-Cl$ $-OH$ $-CH_3$	3-chloro 6-hydroxy 5-methyl

So, the complete name is 3-chloro-6-hydroxy-5-methyl-3-hexen-2-one.