Thiophenol is an organosulfur compound with the formula C
6H
5SH, and sometimes abbreviated as PhSH. This foul-smelling colourless liquid is the simplest aromatic
thiolIn organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur-hydrogen bond . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group...
. The
chemical structureA chemical structure includes molecular geometry, electronic structure and crystal structure of a chemical compound. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together...
s of thiophenols are analogous to
phenolsIn organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group...
except the
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
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.
Thiophenol is an organosulfur compound with the formula C
6H
5SH, and sometimes abbreviated as PhSH. This foul-smelling colourless liquid is the simplest aromatic
thiolIn organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur-hydrogen bond . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group...
. The
chemical structureA chemical structure includes molecular geometry, electronic structure and crystal structure of a chemical compound. Molecular geometry refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together...
s of thiophenols are analogous to
phenolsIn organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group...
except the
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
in the hydroxyl group (-OH) bonded to the aromatic ring is replaced by a
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
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 bondedA covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds...
to an aromatic ring. The organosulfur ligand in the medicine merthiolate is a thiophenol.
Synthesis
Many ways exist to generate thiophenol and related compounds, although thiophenol is usually purchased for laboratory operations.
- Reduction of benzenesulfonyl chloride with zinc
Zinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
.
- 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.
Acidity
Thiophenol has appreciably greater
acidAn acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0...
ity than does phenol. Thiophenol has a
pKaPKA or pKa may be:* Protein kinase A, a cAMP activated protein kinase* pKa, the symbol for Acid dissociation constant* Pi Kappa Alpha, the North-American social fraternity* Public Key Authentication...
's of 6 vs 10 for phenol. A similar pattern is seen for
H2SHydrogen sulfide is the chemical compound with the formula H
2S. This colorless, toxic and flammable gas is partially responsible for the foul odor of rotten eggs and flatulence....
vs. H
2O and all
thiolIn organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur-hydrogen bond . Being the sulfur analogue of an alcohol group , this functional group is referred to either as a thiol group or a sulfhydryl group...
s vs. the corresponding
alcoholIn chemistry, an alcohol is any organic compound in which a hydroxyl group is bound to a carbon atom of an alkyl or substituted alkyl group. An important group of acohols is formed by the simple acyclic alcohols, the general formula for which is C
nH
2n+1OH...
s. Treatment of PhSH with strong base such as
sodium hydroxideSodium hydroxide , also known as lye and caustic soda, is a caustic metallic base. It is used in many industries, mostly as a strong chemical base in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents and as a drain cleaner. Worldwide production in 1998 was around...
(NaOH) or
sodiumSodium is a metallic element with a symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1"...
metal affords the salt sodium thiophenolate (PhSNa).
Alkylation
The thiophenolate is highly nucleophilic, which translates to an high rate of alkylation. Thus, treatment of C
6H
5SH with methyl iodide in the presence of a base gives methyl phenyl sulfide, C
6H
5SCH
3, a
thioetherA thioether is a functional group in organic chemistry that has the structure R1-S-R2 as shown on right. Like many other sulfur-containing compounds, volatile thioethers characteristically have foul odors....
. Such reactions are fairly irreversible. C
6H
5SH also adds to α,β-unsaturated carbonyls via Michael addition.
Oxidation
Thiophenols, expecially in the presence of base is easily oxidized to
diphenyl disulfideDiphenyl disulfide is the chemical compound with the formula [C6H5S]2. This colorless crystalline material is often abbreviated Ph2S2. It is one of the most popular organic disulfides used in organic synthesis...
:
- 2 C6H5SH + 1/2 O2 → C6H5S-SC6H5 + H2O
The disulfide can be reduced back the thiol using
sodium borohydrideSodium borohydride, also known as sodium tetrahydroborate, has the chemical formula NaBH
4. This white solid, usually encountered as a powder, is a specialty reducing agent used in the manufacture of pharmaceuticals and other organic and inorganic compounds...
followed by acidification. This redox reaction is also exploited in the use of C
6H
5SH as a source of H atoms.
Chlorination
Phenylsulfenyl chloride, a blood-red liquid (b.p. 41–42 °C), can be prepared by the reaction of thiophenol with
chlorineChlorine Chlorine Chlorine ( , from the Greek word 'χλωρóς' (khlôros, meaning 'pale green'), is the chemical element with atomic number 17 and symbol Cl. It is a halogen, found in the periodic table in group 17 (formerly VII, VIIa, or VIIb). As the chloride ion, which is part of common salt and...
(Cl
2).
Coordination to metals
Metal cations form thiophenolates, some of which are polymeric. One example is "C
6H
5SCu," obtained by treating
copper(I) chlorideCopper chloride, commonly called cuprous chloride, is the lower chloride of copper, with the formula CuCl.This colorless solid is a versatile precursor to other copper compounds, including some of commercial significance. It occurs naturally as the rare mineral nantokite. Unlike other first-row...
with thiophenol.