Mercaptan:
any of a class of organosulfur compounds is similar to the
alcohol and phenol but containing a sulfur atom in place of the oxygen atom.
Compounds containing -SH as the principal group directly attached to carbon are
named 'thiols'. In substitutive nomenclature their names are formed by adding
'-thiol' as a suffix to the name of the parent compound. When -SH is not the
principal group, the prefix 'mercapto-' is placed before the name of the parent
compound to denote an unsubstituted -SH group. 'thio' is a chemical prefix
indicates the replacement of an oxygen in an acid radical by sulfur with a
negative valence of 2. Sulfur analog of alcohol is called thiol (or mercaptan), and ether analog
is called sulfide.
Sulfate
(also spelled sulphates in Euorpe) is any chemical compound related to sulfuric acid, formed
by replacing one or both of the hydrogens with a metal or a radical. Sulfite is any salt of sulfurous
acid, chemical species H2SO3, which is formed in aqueous solutions of sulfur
dioxide. Sulfurous acid is a clear liquid with a strong sulfur aroma. Sulfide is
a compound having one or more sulfur atoms in which the sulfur is connected
directly to a carbon, metal, or other nonoxygen atom; for example, sodium
sulfide, Na2S. Sulfur compounds are used in the synthesis of medicine and
chemicals, manufacture of wood, pulp and paper. They are used in winemaking,
brewing, food preservation, metallurgy, engraving process, ore flotation,
additive in making steel, bleaching, metal treatment and as an analytic reagent.
The first chemical contrast of thiols and sulfides with
alcohols and ethers is acidity which is important in organic reactions. Thiols
are stronger acids than relevant alcohols and phenols. Thiolate conjugate bases
are easily formed, and are excellent nucleophiles in SN2 reactions of alkyl
halides and tosylates. The nucleophilicity of sulfur is much greater than that
of oxygen, resulting in a number of useful electrophilic substitution reaction
that are rare by oxygen. For example, sulfides form (with alkyl halides) ternary
sulfonium salts, in the same alkylattion of tert-amines quaternary ammonium
salts, whereas ternary oxonium salts are prepared only under extream conditions.
Without exception, sulfoxides, sulfinate salts and sulfite anion also alkylate
on sulfur, despite of the partial negative formal charge on oxygen and partial
positive charge on sulfur. The second character is the oxidation states of
sulfur. Oxygen has only two oxidation states, whereas sulfur covers from –2 to
+6 as follows:
- -2: Hydrogen Sulfide (H2S), sulfides, sulfonium ions
- -1:
disulfides
- 0: S elemental, sulfoxides, sulfenic acids
- +2: sulfones,
sulfinic acids
- +4: sulfonic acids, sulfite esters
- +6: sulfate
esters
One more sulfur compound's contrast with oxygen analog is in oxidation
chemistry. Oxidation of sulfur compounds changes the oxidation state of sulfur
rather than carbon, whereas, oxidation of alcohols to aldehydes and ketones
changes the oxidation state of carbon not oxygen. Thiols is oxidized to S-S
single bond (disufide) which is stronger than O–O bond in peroxide. Disufide
forms sulfenyl chlorides (with chlorine in mild condition) or sulfonic acids
under harder condition. Oxidation of sulfides with hydrogen peroxide (or
peracids) yields sulfoxides and then to sulfones. A certain sulfoxide compound
such as dimethyl sulfoxide can be used as an effective oxygen source in the
oxidation reaction of primary and secondary alcohols to aldehydes and ketones.
DMSO easily is reduced to dimethyl sulfide and water is taken up by the
electrophile. oxidation procedure is very mild and tolerates a variety of other
functional groups, including those having oxidizable nitrogen and sulfur
atoms.
Organosulfur compounds are widely used in refineries, steamcrackers,
aromatic extraction and petrochemical manufacturing as they acts as
hydrotreating catalysts, initial catalyst improvers, sulfur source and catalyst
presulfiding. Sulfoxide (R2SO) is any of various organic sulfur compounds having
the group -SO (sulfinyl group) whereas sulfone (RSOOR) with the group -SO2
(sulfonyl group). They are derived from oxidation of sulfides. They are widely
used as solvent of both extraction and reaction as well as intermediates for the
synthesis of textile chemicals and pharmaceuticals and agrochemicals. Dimethyl
Sulfoxide is used as an effective extraction solvent and solvent improver for
the separation of aromatic compounds (benzene, toluene and xylenes) from
aliphatic hydrocarbons, and for fractionation of unsaturated components (olefins
and alkynes) from saturated feedstock. It is used as a thermally stable medium
for carrying out chemical reactions to make pharmaceuticals, agrochemicals
(especially pyrethroid insecticides) paint and coating materials and biocides.
Its pharmaceutical grade can be used as a as a local analgesic and
anti-inflammatory agent. Sulfolane is used as a extraction as well as a reaction
solvent. It is used to separate aromatic hydrocarbons (benzene, toluene and
xylenes), It is used to separate n-propyl alcohol and sec-butyl alcohol. It is
used to purify natural gas streams and for fractionation of fatty acids into
saturated and unsaturated components. It is used as a reaction solvent for the
preparation of aromatic sulfonic acids, pyridines, isocyanates and
pharmaceuticals. It can also be involved in the halogen exchange process and
polymerization process. It is used as a plasticizer and curing agent.
Organosulfur compounds have diverse applications in the organic synthesis as
organosulfur sources into target organic molecules in the manufacture of
pharmaceuticals, adhesives, biocides, agrochemical products, lubricant and fuel
additives for high pressure, surfactants, water treatment chemicals, dyes,
flavors & fragrances, and photographic chemicals.
Sulfonamide is an
organic sulfur compounds containing the radical -SO2NH2 (the amides of sulfonic
acids). Its molecular structure is similar to p-Aminobenzoic acid (PABA) which
is needed in bacteria organisms as a substrate of the enzyme dihydropteroate
synthetase for the synthesis of tetrahydrofolic acid (THF). Sulfonamides,
derived from chiefly sulfanilamide, are capable of interfering with the
metabolic processes in bacteria that require PABA. They act as antimicrobial
agents by inhibiting bacterial growth and activity and called sulfa drugs. They
are used in the prevention and treatment of bacterial infections, diabetes
mellitus, edema, hypertension, and gout.
Diethyl Sulfide is used as a solvent for a wide range of organic and
inorganic materials. It is one of the simplest organic substance containing
sulfur, used as a presulfiding agent for catalysts in the refinery and
petrochemical manufacturing process especially in the ethylene manufacturing to
control the formation of coke and carbon monoxide. It is also used in steel mill
furnaces to control dusting. It is a chemical intermediate for wide range of
organic synthesis.
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