# Why H2S2 is hydrogen disulfide and not hydrogen persulfide?

Context: I was checking this question and in the answer, the compound $$\ce{FeS2}$$ was named "iron disulphide" (it was previously named "iron persulfide" but later changed after responding to the comments).

The structure of "hydrogen disulfide" is quite analogous to hydrogen peroxide i.e. containing the sulfur-sulfur linkage bond ($$\ce{-S-S -}$$) similar to peroxide bond. The bond angles of both compounds are also similar. So, why name it "disulfide" instead of "persulfide"?

In a group, compound are named in a similar manner in order to follow a certain fashion/trend. For e.g. methane, silane, germane (group 14). So, why $$\ce{H2O2}$$ is hydrogen peroxide and $$\ce{H2S2}$$ is hydrogen disulfide? Why isn't it named hydrogen persulfide as per analogy?

• – DHMO
Oct 29 '16 at 14:58
• Hydrogen peroxide can be alternatively called dihydrogen dioxide (note the prefix -di). As such, $\ce{FeS_2}$ could be called either iron(II) persulfde or iron(II) disulfide. Structurally speaking, though, in both cases the per-option is more appropriate. Oct 29 '16 at 18:12

"Hydrogen persulfide" is technically a very crude mixture of various hydrogen polysulfides ($$\ce{H2S_n ; n\geq2}$$). It has long sulfur chains and is formulated as $$\ce{H-(S)_{n}-H}$$. To avoid confusion, each members of the mixture is named according to number of sulfur atoms. So, $$\ce{H2S2}$$ is hydrogen disulfide.