Editing Thiol (section)

==Preparation==
In industry, methanethiol is prepared by the reaction of [[hydrogen sulfide]] with [[methanol]]. This method is employed for the industrial synthesis of [[methanethiol]]:
:CH<sub>3</sub>OH + H<sub>2</sub>S → CH<sub>3</sub>SH + H<sub>2</sub>O
Such reactions are conducted in the presence of acidic catalysts. The other principal route to thiols involves the addition of hydrogen sulfide to [[Alkene|alkenes]]. Such reactions are usually conducted in the presence of an acid catalyst or UV light. [[Halogen|Halide]] displacement, using the suitable organic halide and sodium hydrogen sulfide has also been used.<ref>John S Roberts, "Thiols", in ''Kirk-Othmer Encyclopedia of Chemical Technology'', 1997, Wiley-VCH, Weinheim.  {{doi|10.1002/0471238961.2008091518150205.a01}}</ref>

Another method entails the alkylation of [[sodium hydrosulfide]].
: RX + NaSH → RSH + NaX{{pad|3em}}(X = Cl, Br, I)
This method is used for the production of [[thioglycolic acid]] from [[chloroacetic acid]].

===Laboratory methods===
In general, on the typical laboratory scale, the direct reaction of a [[halogenoalkane|haloalkane]] with sodium hydrosulfide is ''in''efficient owing to the competing formation of sulfides. Instead, alkyl halides are converted to thiols via an ''S''-alkylation of [[thiourea]]. This multistep, one-pot process proceeds via the intermediacy of the [[isothiouronium salt]], which is hydrolyzed in a separate step:<ref>{{OrgSynth | author = Speziale, A. J. | title = Ethanedithiol | collvol = 4 | collvolpages = 401 | year = 1963 | prep = cv4p0401}}.</ref><ref>{{cite journal|first1=G. G. |last1=Urquhart|first2=J. W. Jr. |last2=Gates|first3=Ralph|last3=Connor|journal=Org. Synth.|year=1941|volume=21|page=36|title=''n''-Dodecyl Mercaptan|doi=10.15227/orgsyn.021.0036}}</ref>

: CH<sub>3</sub>CH<sub>2</sub>Br + SC(NH<sub>2</sub>)<sub>2</sub> → [CH<sub>3</sub>CH<sub>2</sub>SC(NH<sub>2</sub>)<sub>2</sub>]Br
: [CH<sub>3</sub>CH<sub>2</sub>SC(NH<sub>2</sub>)<sub>2</sub>]Br + NaOH → CH<sub>3</sub>CH<sub>2</sub>SH + OC(NH<sub>2</sub>)<sub>2</sub> + NaBr

The thiourea route works well with primary halides, especially activated ones. Secondary and tertiary thiols are less easily prepared. Secondary thiols can be prepared from the ketone via the corresponding [[Thioketal|dithioketals]].<ref>{{OrgSynth | author = S. R. Wilson, G. M. Georgiadis | title = Mecaptans from Thioketals: Cyclododecyl Mercaptan | collvol = 7 | collvolpages = 124 | year = 1990 | prep = cv7p0124}}.</ref> A related two-step process involves alkylation of thiosulfate to give the thiosulfonate ("[[Bunte salt]]"), followed by hydrolysis. The method is illustrated by one synthesis of [[thioglycolic acid]]:
:ClCH<sub>2</sub>CO<sub>2</sub>H + Na<sub>2</sub>S<sub>2</sub>O<sub>3</sub> → Na[O<sub>3</sub>S<sub>2</sub>CH<sub>2</sub>CO<sub>2</sub>H] + NaCl

:Na[O<sub>3</sub>S<sub>2</sub>CH<sub>2</sub>CO<sub>2</sub>H] + H<sub>2</sub>O → HSCH<sub>2</sub>CO<sub>2</sub>H + NaHSO<sub>4</sub>

[[Organolithium compound]]s and [[Grignard reagent]]s react with sulfur to give the thiolates, which are readily hydrolyzed:<ref>{{OrgSynth | author = E. Jones and I. M. Moodie | title = 2-Thiophenethiol | collvol = 6 | collvolpages = 979 | year = 1990 | prep = cv6p0979}}.</ref>
:RLi + S → RSLi
:RSLi + HCl → RSH + LiCl

Phenols can be converted to the thiophenols via rearrangement of their ''O''-aryl dialkylthiocarbamates.<ref>{{OrgSynth | author = Melvin S. Newman and Frederick W. Hetzel | title = Thiophenols from Phenols: 2-Naphthalenethiol | collvol = 6 | collvolpages = 824 | year = 1990 | prep = cv6p0824}}.</ref>

Thiols are prepared by reductive dealkylation of sulfides, especially benzyl derivatives and thioacetals.<ref>{{OrgSynth |first1=Ernest L. |last1=Eliel |first2=Joseph E. |last2=Lynch |first3=Fumitaka |last3=Kume |first4=Stephen V. |last4=Frye | title = Chiral 1,3-oxathiane from (+)-Pulegone: Hexahydro-4,4,7-trimethyl-4''H''-1,3-benzoxathiin | collvol = 8 | collvolpages = 302 | year = 1993 | prep = cv8p0302}}</ref>

Thiophenols are produced by ''S''-arylation or the replacement of diazonium leaving group with sulfhydryl anion (SH<sup>−</sup>):<ref>{{cite journal|title=Novel One-Pot Synthesis of Thiophenols from Related Triazenes under Mild Conditions|journal=Synlett|date=2012|volume=23|issue=13|pages=1893–1896|doi=10.1055/s-0032-1316557|last1=Kazem-Rostami|first1=Masoud|last2=Khazaei|first2=Ardeshir|last3=Moosavi-Zare|first3=Ahmad|last4=Bayat|first4=Mohammad|last5=Saednia|first5=Shahnaz|s2cid=196805424 }}</ref><ref>{{cite journal|last1=Leuckart |first1=Rudolf |title=Eine neue Methode zur Darstellung aromatischer Mercaptane |trans-title=A new method for the preparation of aromatic mercaptans |journal=Journal für Praktische Chemie |date=1890 |series= 2nd series |volume=41 |pages=179–224 |url=https://books.google.com/books?id=KxlLAAAAYAAJ&pg=PA179 |doi=10.1002/prac.18900410114 |language=de }}</ref>
:{{chem|ArN|2|+}} + SH<sup>−</sup> → ArSH + N<sub>2</sub>