Compounds Containing Bivalent Sulfur

C-5.0. Introduction

502 - A key role has long been played by the syllables "thio", and this practice is retained. In nearly all its applications "thio" denotes replacement of oxygen by sulfur; the distinction from "thia" which denotes replacement of carbon in a ring or chain (see Rules B-1.1 and C-61.1) should be noted. Usually, "thio" (denoting replacement of oxygen) is placed in front of the name of an affix that denotes an oxygen-containing group or an oxygen atom; for example, "ol" denotes OH, so "thiol" denotes SH; "one" denotes (C)=O, so "thione" denotes (C)=S; "oic acid" denotes , so "thioic acid "denotes and "dithoic acid" denotes However, there are some types of name where this procedure is not followed . For instance, (1) by long custom, where an acid has a trivial name, "thio" is placed in front of that name, so that, for example, thioacetic acid is the name for the acid (2) For sulfur derivatives of carboxylic acids, names ending in "-carbothioic acid" () and "-carbodithioic acid" are used. (3) Particular difficulty arises with prefixes for the groups HS- and RS-, largely owing to differing uses of "hydroxy and "oxy'' in various languages; of the various possibilities it has seemed best to retain "mercapto-" as prefix for HS-, and "thio-" for the bivalent atom -S-. Occasionally this last use of "thio" may require parentheses for distinction from its use for replacement of oxygen in a trivially named acid, as in:

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Thiols and related compounds Rule C-511, Rule C-513, Rule C-514, Rule C-515
Sulfenic Acids and Their Derivatives Rule C-521
Thioaldehydes (Monomeric), Tioketones, and Tioacetals Rule C-531, Rule C-532, Rule C-533
Thiocarboxylic Acids and Thiocarbonic Acid Derivatives Rule C-541, Rule C-542, Rule C-543 , Rule C-544, Rule C-545, Rule C-546, Rule C-547 , Rule C-548
Sulfonium Compounds Rule C-551