Hantzsch-Widman nomenclature

The Hantzsch-Widman nomenclature is recommended for 3- to 10-membered heterocycles. For larger ring heterocycles, replacement nomenclature should be used. 

It should be noted that in some cases, for example, for pyridine, the trivial name has become a permitted trivial name and should be used as the systematic name instead of the Hantzsch-Widman indication (see below). 

The type of heteroatom is indicated by a prefix according to Table 2.1. The sequence in this table also indicates the preferred order of prefixes principle of decreasing priority). 

The ring size is indicated by a suffix according to Table 2.2. Some of the syllables are derived from Latin numerals, namely ir from tri, et from tetra, ep from hepta, oc from octa, on from nona, and ec from deca. 

The compound with the maximum number of noncumulative double bonds is regarded as the parent compound of the monocyclic systems of a given ring size. The naming is carried out by combining one or more prefixes from Table 2.1 with a suffix from Table 2.2. If two vowels succeed one another, the letter a is omitted from the prefix, for example, azirine (notazairine). 

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Handylab, 26 976 Hanford N reactor, 17 572-573 Hanford production reactors, 17 570 Hanksite, 5 785t Hansa yellows, 14 317 Hansch equation, 10 329 Hansenula polymorpha, 12 479 Hantaviruses, 3 137 Hantzsch pyridine synthesis, 16 550 Hantzsch-Widman nomenclature system, 17 399... 

Table 4 The a prefixes used in Hantzsch-Widman nomenclature.

We summarize here the rules of the so-called Hantzsch-Widman nomenclature system for heterocycles, which currently is the fashionable procedure, although relegated to second-class status by a recent, very practical approach to organic nomenclature.1... 

Owing to the numerous possibilities in which a 1,4-diene can be assembled, especially when heteroatoms are included, a nomenclature issue arises that needs to be addressed from the outset. According to the Hantzsch-Widman nomenclature system in combination with the lUPAC rules, hetera-di-ir-meth-ane reactions are those transformations in which a particular heteroatom replaces the caiixin atom of the 1,4-diene moiety the position is specified by means of a numerical prefix. We will use this suggested nomenclature for the di-Tr-methane photorearrangement as indicated for the substrates shown in Scheme 1. 

IR-6.2.4.1 Heteronuclear acyclic parent hydrides in general IR-6.2.4.2 Hydrides consisting of chains of alternating skeletal atoms IR-6.2.4.3 Heteronuclear monocyclic parent hydrides Hantzsch-Widman nomenclature IR-6.2.4.4 Skeletal replacement in boron hydrides IR-6.2.4.5 Heteronuclear polycyclic parent hydrides IR-6.3 Substitutive names of derivatives of parent hydrides IR-6.3.1 Use of suffixes and prefixes IR-6.3.2 Hydrogen substitution in boron hydrides IR-6.4 Names of ions and radicals derived from parent hydrides... 

Heteronuclear monocyclic parent hydrides Hantzsch-Widman nomenclature... 

Last part of endings of a number of parent names of saturated heteromonocycles in Hantzsch-Widman nomenclature, i.e. of irane , etane , olane , ane , inane , epane , ocane , onane and ecane (see Section IR-6.2.4.3). 

Ending of parent names of ten-membered saturated heteromonocycles in Hantzsch-Widman nomenclature, cf. Section IR-6.2.4.3. 

General ending of parent names of three-membered heteromonocycles with the maximum number of non-cumulative double bonds (i.e. one double bond) in Hantzsch-Widman nomenclature, cf. Section IR-6.2.4.3. See also irine . 

Abstracts, only the Hantzsch-Widman nomenclature has been used. Occasionally, one encounters names not strictly in accordance with prescribed terminology, e.g., azocane or azacyclooctane to denote the saturated, eight-membered heterocycle containing one nitrogen. In this article, we are more concerned with clarity, than with the consistent use of IUPAC nomenclature. 

Every heterocyclic compound can be referred back to a parent ring system. These systems have only H-atoms attached to the ring atoms. The lUPAC rules allow two nomenclatures. The Hantzsch-Widman nomenclature is recommended for three- to ten-membered heterocycles. For larger ring heterocycles, replacement nomenclature should be used. 

The Hantzsch-Widman nomenclature can only be applied to the first example and this then results in different numbering. 

It should be pointed out that currently both trivial and systematic names are commonly used for naming the heterocyclic compounds. For example, an organic chemist will recognize without any difficulty the structures connected to names such as furane, pyrrole, pyrrolidine, pyrazole, imidazole, pyridine, or piperidine, despite the fact that all these names are trivial. On the other hand, the complex heterocycles require more sophisticated approaches in order to avoid ambiguity and correctly translate the chemical strucmre into the name. For these, compound names are often made using either trivial name (e.g., indazole for benzopyrazole, benzimidazole, indole, and isoindole) or the Hantzsch-Widman nomenclature, for example, 1,2,3- or 1,2,5-oxadiazoles, 1,3-dioxolane, 1,2- or 1,3-dithiolane, and 1,3- or 1,4-dioxane. It should be noted that the Hantzsch-Widman nomenclature treats the unsaturated heterocycle with maximum number of conjugated double bonds as parent compound. This adds another layer of complexity, giving rise to names such as... 

Hantzsch-Widman nomenclature 6 Hellebriginin 311 Hematin 555 Hemin 555 Hemoglobin 555 Hetarenes 4 Heterocycloalkanes 2 Heterocycloalkenes 2 Heteronins 549 Hexachlorophene 439 Hexetidine 472 Hexobarbital 473 Histamine 227 Histidine 227 Histrionicotoxin 433 Hydantoin 235 Hydrogen, indicated 10 1-Hydroxybenzotriazol 267 4-Hydroxyproline 161 8-Hydroxyquinoline 405... 

Finally there is the Hantzsch-Widman nomenclature for 5- and 6-membered rings, extended in the Ring Index and adopted in the lUPAC 1957 rules, by which any monocyclic heterocompound with 3-10 members in the ring can be named in a systematic way. Syllables oxa, thia, aza (as above), etc., denote the heteroatoms and are combined with syllables representing ring size, the positions of the heteroatoms being denoted by numerals. The full rules (see... 

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