Thiathiophthenes

Other names can be found in the literature for structure 10, namely, thiothiophthene and thiathiophthene. Thiothiophthene is questionable because, in systematic replacement nomenclature, the affix thio must indicate the replacement of oxygen by sulfur and not of carbon by sulfur. 

Thiathiophthene is a better choice, provided a locant be given to thia (6aIUPAC nomenclature to derive a replacement name from the trivial name of a heterocyclic system (thiophthene). 

Finally some compounds related to the thiathiophthene no-bond resonance system may be regarded as containing contributions from isothiazolium forms (8 <-> 9).146... 

In replacement nomenclature, the name of a heterocyclic compound is formed by prefixing a terms, such as oxa , thia , aza , etc. to the name of the corresponding cyclic hydrocarbon. As IUPAC Rule B-4 states that the replacement method should be applied to a homocyclic hydrocarbon, we use pentalene for this purpose. The replacement procedure forbids the use of heterocyclic parent structures and for this reason the name thiathiophthene , which is found in the literature, is not in compliance with IUPAC recommendations. Another name which is sometimes found is thiothiophthene , which is even worse because of an incorrect use of the prefix thio . 

Gerson and co-workers" " " some years ago reported an analysis of the ESR spectrum of the anion-radical 233 of 2,5-diphenyl[l,2,4]dithiazolo-[l,5-fe][l,2,4]dithiazole. Some of the work reported at the same time concerning anion-radicals of analogous 6a-thiathiophthenes was subsequently reinterpreted." " However, the inference from footnote 7 in Gerson et al. is that the results for 233 are not superseded. (Hyperfine splittings indicated for 233 are in gauss.)... 

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