Formazan
class of chemical compounds
The formazans are compounds of the general formula [R−N=N−C(R')=N−NH−R"], formally derivatives of formazan [H2NN−CHN=NH], unknown in free form.
Formazan dyes are artificial chromogenic products obtained by reduction of tetrazolium salts by dehydrogenases and reductases. They have a variety of colors from dark blue to deep red to orange, depending on the original tetrazolium salt used as the substrate for the reaction.
Structure and reactivity
Formazans are intensely colorful compounds characterized by the following structure: [−N=N−C(R)=N−NH−], and are closely related to azo (−N=N−) dyes. Their structure was first defined in 1892, by von Pechmann and by Bamberger and Wheelwright independently. Their deep colour and redox chemistry derive from their nitrogen-rich backbone.
Formazans have a high tautomeric and conformational flexibility. Due to the two alternating double bonds in the backbone, formazans can exist in four possible isomeric forms: syn, s-cis (closed form); syn, s-trans (open form); anti, s-cis; and anti, s-trans (linear form).
1,5-disubstituted formazans can exist as two tautomers (1 and 2 in the image below). Upon deprotonation, the formed anion (3) is stabilized by resonance.
This brief starts where responsible research should: with the source description of “Formazan” as class of chemical compounds. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the science & nature register because the source frames it as class of chemical compounds. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The date and method of observation matter as much as the stated conclusion, especially where classification or consensus has changed. The source revision retrieved here is dated Apr 20, 2026. The linked authority identifier is Q2324668. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1892.
Scientific names, classifications and consensus can change while older terminology persists in catalogues and historical literature. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Check terminology, classification and the date of the cited evidence. Scientific names and technical consensus can change while older records retain historical value.
- Current terminology
- Classification context
- Finding cited technical literature
Primary datasets, specimen catalogues, standards bodies and the most recent peer-reviewed literature.
Three-step research path
- Establish the record: confirm the title “Formazan”, its source revision and the description used here.
- Expand the search: follow Formazan primary sources, Formazan archive and Formazan research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Formazan”?
- Is the terminology current, historical or disputed?
- Which observation, specimen, dataset or publication supports the account?
Search terms from this dossier
This entry incorporates text from “Formazan” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.