Thio- prefix

Bivalent Sulfur. The prefix thio, placed before an affix that denotes the oxygen-containing group or an oxygen atom, implies the replacement of that oxygen by sulfur. Thus the suffix -thiol denotes — SH, -thione denotes —(C)=S and implies the presence of an =S at a nonterminal carbon atom, -thioic acid denotes [(C)=S]OH [(C)=0]SH (that is, the O-substituted acid and the 5-substi-... 

Organosulfur Halides. When sulfur is directly linked only to an organic radical and to a halogen atom, the radical name is attached to the word sulfur and the name(s) and number of the halide(s) are stated as a separate word. Alternatively, the name can be formed from R—SOH, a sulfenic acid whose radical prefix is sulfenyl-. For example, CH3CH2—S — Br would be named either ethylsulfur monobromide or ethanesulfenyl bromide. When another principal group is present, a composite prefix is formed from the number and substitutive name(s) of the halogen atoms in front of the syllable thio. For example, BrS—COOH is (bromothio)formic acid. 

Radicals analogous to the above containing other chalcogens in place of oxygen are named by adding the prefixes thio-, seleno-, and so on for example, PS, thiophosphoryl CS, thiocarbonyl. 

By long tradition, a group of cationic pyran derivatives have trivial names, i.e. (186)-(189), which are retained by lUPAC. These names may be modified by the prefixes thio-, seleno-and telluro- for their chalcogen analogs. 

Thioesters are named like the corresponding esters. If the related ester has a common name, the prefix thio- is added to the name of the carboxylate acetate becomes thioacetate, for instance. If the related ester has a systematic name, the -oate or -carboxylate ending is replaced by -thioate or -carbothioate butanoate becomes butanelhioate and cyclohexanecarboxylate becomes cyclohexane-carbothioate, for instance. 

Replacement of a hydroxy oxygen atom of an aldose or ketose, or of the oxygen atom of the carbonyl group of the acyclic form of an aldose or ketose, by sulfur is indicated by placing the prefix thio , preceded by the appropriate locant, before the systematic or trivial name of the aldose or ketose. 

Note. The appropriate prefix is thio, not thia the latter is used in systematic organic chemical nomenclature to indicate replacement of CH2 by S. 

Note. It is common practice in carbohydrate names to regard thio as detachable, and therefore alphabetized with any other prefixes. 

Spiro systems can be named by normal procedures [13]. For clarity, any anhydro or deoxy prefixes or chalcogen replacement prefixes (e.g. thio) referring to the spiro... 

The prefix thio- indicates that sulfur is present, usually as a replacement for one or more oxygen atoms in a compound whose name is familiar. For example, in thiosulfuric acid, one 0 atom of sulfuric acid has been replaced by an S atom in thiocyanic acid, the only 0 atom of cyanic acid has been replaced in thioar-senic acid, all of the O atoms of arsenic acid have been replaced by S. The rules of naming do not normally show how many 0 atoms are replaced. HSCN is placed in Table 8-3 because of the many similarities between oxygen and sulfur. 

Sulphur, in accord with its similarity to oxygen, can be substituted for it in many of its compounds without essentially altering their chemical nature, and the compounds thus obtained have the same nomenclature as the corresponding oxygen compounds, except that the prefix thio or sulpho is used. Thus sulpho-salts are produced in the same manner as the oxy-salts above ... 

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 . 

The prefix "thio" in the name of a polyatomic ion means that an oxygen atom in the root "ate" ion has been replaced by a sulfur atom. For example, the sulfate ion is SCfi2-, while the thiosulfate ion is S2032-. Notice that the valence does not change. 

Thioesters are named like esters, using the prefix thio- before the name of the carboxylic acid. 

Normally (11) and (12) are indistinguishable either form can be isolated by salt or ester formation. Compound (11) is termed the O-acid (thiono) and (12) the S-acid (thiolo). For simple acids, the prefix thio is used for example, MeCH2CH2COSH is thiobutyric acid. For more complex structures, the suffix thioic acid is used for example,... 

Thioaldehydes are generally very unstable. Thioketones may sometimes be named by putting the prefix thio in front of the name of a simple ketone, e.g. thiobenzophenone, but generally by replacing the terminal one of ketones by thione thus,... 

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