Thiophenol
IUPAC name	Thiophenol
Other names	Benzenethiol
Identifiers
CAS number	108-98-5 Y
RTECS number	DC0525000
SMILES	c1ccccc1S
Properties
Molecular formula	C6H6S
Molar mass	110.19 g/mol
Appearance	colorless liquid
Density	1.0766 g/mL
Melting point	-15 °C
Boiling point	169 °C
Hazards
R-phrases	R10 R24/25 R26 R41
S-phrases	S23 S26 S28 S36/37/39 S45
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Thiophenol is an organosulfur compound with the formula C₆H₅SH, and sometimes abbreviated as PhSH. This foul-smelling colourless liquid is the simplest aromatic thiol. The chemical structures of thiophenols are analogous to phenols except the oxygen atom in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a sulfur atom. The prefix thio- implies a sulfur-containing compound and when used before a root word name for a compound which would normally contain an oxygen atom, thio- commonly means that the oxygen atom is replaced by a sulfur atom.

Thiophenols also describes a class of compounds formally derived from thiophenol itself. All have a sulfhydryl group (-SH) covalently bonded to an aromatic ring. The organosulfur ligand in the medicine merthiolate is a thiophenol.

Contents 1 Synthesis 2 Properties 2.1 Acidity 2.2 Alkylation 2.3 Oxidation 2.4 Chlorination 2.5 Coordination to metals 3 Safety 4 References

[edit] Synthesis

Many ways exist to generate thiophenol and related compounds, although thiophenol is usually purchased for laboratory operations.

• Reduction of benzenesulfonyl chloride with zinc.^[1]
• Action of elemental sulfur on phenyl magnesium halide or phenyllithium followed by acificiation.

Phenols can be converted to the thiophenols via rearrangement of their O-aryl dialkylthiocarbamates.^[2]

[edit] Properties

[edit] Acidity

Thiophenol has appreciably greater acidity than does phenol. Thiophenol has a pK_a's of 6 vs 10 for phenol. A similar pattern is seen for H₂S vs. H₂O and all thiols vs. the corresponding alcohols. Treatment of PhSH with strong base such as sodium hydroxide (NaOH) or sodium metal affords the salt sodium thiophenolate (PhSNa).

[edit] Alkylation

The thiophenolate is highly nucleophilic, which translates to an high rate of alkylation.^[3] Thus, treatment of C₆H₅SH with methyl iodide in the presence of a base gives methyl phenyl sulfide, C₆H₅SCH₃, a thioether. Such reactions are fairly irreversible. C₆H₅SH also adds to α,β-unsaturated carbonyls via Michael addition.

[edit] Oxidation

Thiophenols, expecially in the presence of base is easily oxidized to diphenyl disulfide:

2 C₆H₅SH + 1/2 O₂ → C₆H₅S-SC₆H₅ + H₂O

The disulfide can be reduced back the thiol using sodium borohydride followed by acidification. This redox reaction is also exploited in the use of C₆H₅SH as a source of H atoms.

[edit] Chlorination

Phenylsulfenyl chloride, a blood-red liquid (b.p. 41–42 °C), can be prepared by the reaction of thiophenol with chlorine (Cl₂).^[4]

[edit] Coordination to metals

Metal cations form thiophenolates, some of which are polymeric. One example is "C₆H₅SCu," obtained by treating copper(I) chloride with thiophenol.^[5]

[edit] Safety

Thiophenol is highly toxic.

[edit] References

1. ^ Adams, R.; C. S. Marvel, C. S., "Thiophenol", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1p0504 ; Coll. Vol. 1: 504 
2. ^ Melvin S. Newman and Frederick W. Hetzel (1990), "Thiophenols from Phenols: 2-Naphthalenethiol", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0824 ; Coll. Vol. 6: 824 
3. ^ Campopiano, O. "Thiophenol" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
4. ^ Barrett, A. G. M.; Dhanak, D.; Graboski, G. G.; Taylor, S. J. (1993), "(Phenylthio)nitromethane", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv8p0550 ; Coll. Vol. 8: 550 
5. ^ Posner, G. H.; Whitten, C. E., "Secondary and Tertiary Alkyl Ketones from Carboxylic Acid Chlorides and Lithium Phenylthio(alkyl)cuprate Reagents: tert-Butyl Phenyl Ketone", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0248 ; Coll. Vol. 6: 248