Nomenclature of Inorganic Chemistry: Inorganic Acids and Derivatives

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(b) to list the ‘acid’ names that are still acceptable due to common usage and/or because they are needed in organic nomenclature (see Tables IR-8.1 and IR-8.2).

Referencing norms: ListedNameStaysAcceptable

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Based on these considerations, the use of the word ‘acid’ in any new name in inorganic nomenclature is discouraged. However, a number of the existing ‘acid’ names are so commonly used (sulfuric acid, perchloric acid, etc.) that it would be unrealistic to suggest replacing them altogether by systematic alternatives. Another reason to include them in the present recommendations is that the acids in question are used as parent structures in the nomenclature of certain organic (i.e. carbon-containing) derivatives so that the derivative names are directly or indirectly based on the names containing the word ‘acid’. See examples below and Section IR-8.6.

Referencing norms: NewAcidWordNameIsDiscouraged/R1, NewAcidWordNameIsDiscouraged/R2, NewAcidWordNameIsDiscouraged/priority

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Finally, names which do not denote compounds of a definite composition, such as hydrochloric acid, stannic acid, tungstic acid, etc., are outside the scope of the systematic nomenclature presented here. However, the chemical systems involved can always be discussed using systematic names such as hydrogen chloride, tin(IV) oxide, tungsten(VI) oxide, etc.

Referencing norms: IndefiniteCompositionIsOutsideTheScope

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Thus, this Chapter provides several acceptable names for many inorganic acids; it is left to practitioners to choose the name most suitable for a particular application. In the future, IUPAC aims to select preferred names for inorganic species, including the acids dealt with here, just as Ref. 1 does for organic species.

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Note that there is one general case where the word ‘acid’ may appear in a fully systematic name of an inorganic compound, namely when substitutive nomenclature is used and prescribes a suffix for the highest ranking substituent group which ends with the word ‘acid’.

Referencing norms: SubstitutiveSuffixKeepsTheWord

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All such acids may also be given structure-based systematic names using principles already described in preceding chapters on substitutive and additive nomenclature, so in that respect the ‘acid’-containing names are superfluous. Furthermore, many species which would be classified as acids based on their chemical properties are never named as such, e.g. aqua ions such as hexaaquaaluminium(3þ), and hydrides and derivatives such as ammonium, hydrogen sulfide (sulfane), etc. The term ‘acid’ is thus not used consistently.

Referencing norms: AdditiveNameIsAlwaysAvailable

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The method called ‘acid nomenclature’ in Section I-9.6 of Ref. 2 is little used and not needed. Its use is therefore no longer recommended.

Referencing norms: AcidNomenclatureIsNoLongerRecommended

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Molecular compounds and ions commonly regarded as inorganic acids are treated no differently than other molecular species when constructing systematic names. The most easily applied general principle for systematic naming is that of additive nomenclature, exemplified in Section IR-8.3. As mentioned in Section IR-8.1, substitutive nomenclature could also be generally applied. However, this is not further elaborated here. Sections IR-8.4 and IR-8.5 describe hydrogen names, which are related to additive names and only needed in special cases.