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R-0.1.7 Elision and addition of vowels

R- Vowels are systematically elided as follows:

(a) the terminal "e" in names of parent hydrides when followed by a suffix beginning with "a", "i", "o", "u", or "y";

Examples to R-

Ethanal (R-5.6.1)

Ethanamine (R-5.4.1)

Heptan-2-one (R-

Pent-4-en-2-ol (R-4.2.3)

Sulfanyl (R-

Methanium (R-5.8.2)

Propan-2-ide (R-5.8.3)

(b) in the Hantzsch-Widman system, the final "a" of an element prefix when followed by a vowel;

Examples to R-

1,3-Oxazole (R-2.3.3)

(not 1,3-Oxaazole nor 1,3-Oxaazaole)

1,4-Thiazepine (R-2.3.3)

(not 1,4-Thiaazepine nor 1,4-Thiaazaepine)

(c) the terminal "a" in the names of numerical multiplicative affixes when followed by a suffix beginning with "a" or "o", or a Hantzsch-Widman prefix or stem beginning with a vowel;

Examples to R-

Benzenehexol (R-

(not Benzenehexaol)

[1,1'-Binaphthalene]-3,3',4,4'-tetramine (R-5.4.1)

(not [1,1'-Binaphthalene]-3,3',4,4'-tetraamine)

1,3,5,7-Tetraoxocane (R-2.3.3)

(not 1,3,5,7-Tetraoxaocane)

(d) the terminal "a" of an element prefix in "ababa" repeating unit names (see R- and the terminal "o" of a replacement infix when followed by a vowel;

Examples to R-

Tetrasiloxane (R-

(not Tetrasilaoxane) P-Phenylphosphonamidimidic acid (R-3.4)

(not P-Phenylphosphonamidoimidic acid)

R- There is no elision of vowels in the following cases:

(a) in conjunctive names;

Examples to R-

Cyclohexaneethanol (R-

Cyclopentaneacetic acid (R-

(b) from replacement or numerical prefixes in replacement nomenclature;

Example to R-

2,4,8,10-Tetraoxaundecane (R-

(c) from numerical prefixes in multiplying parent compounds;

Example to R-

Ethylenediaminetetraacetic acid (R-9.1, Table 28(b))

(d) from numerical prefixes before substituent prefix names;

Example to R-


acid (R-

(e) in composite prefixes;

Examples to R-

4-(Thioacetyl)benzoic acid (R-5.6.1)

[Oxybis(ethyleneoxy)]diacetic acid (R-4.2.6)

(f) from prefixes designating attached components in fusion nomenclature; for example the terminal "o" of acenaphtho-, benzo-, naphtho-, perylo-, phenanthro- and the terminal "a" of anthra-, cyclopropa-, cyclobuta-, etc., are not elided before a vowel as in the 1979 edition of the IUPAC Nomenclature of Organic Chemistry.

Examples to R-

Dibenzo[b,e]oxepine (R-

(previously, Dibenz[b,e]oxepin)

5H-Cyclobuta[f]indene (R-

(previously, 5H-Cyclobut[f]indene)


R- Addition of the vowel "o". For euphonic reasons, the vowel "o" is sometimes inserted between consonants.

Examples to R-

Naphthalene-2-sulfonodiimidic acid (R- Ethanesulfonohydroximic acid (R- Diethylphosphinothioic chloride (R-5.7.6)

R-0.1.8 Order of prefixes

This HTML reproduction is as close as possible to the published version [see IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC]. If you need to cite these rules please quote this reference as their source.

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