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. Thiol 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.
Thiophene,
also known as Thiofuran, is a cyclic compound containing four carbon atoms and
one sulphur atom in a ring. It is a toxic, flammable, highly reactive, colorless
liquid insoluble in water (soluble in alcohol and ether) and melts at 38 C,
boils at 84 C. It is used as a solvent and chemical intermediate. Its
derivatives are widely used in manufacturing dyes, aroma compounds and
pharmaceuticals. They are used as monomers to make condensation copolymers.
Thiosulfate
is a salt containing the negative ion S2O32-, a analog of the
sulfate ion (SO42-) where one of the
oxygen (O) atoms has been replaced by a sulfur atom. The sulfur atoms of the
thiosulfate ion are not equivalent. Thiosulfate is tetrahedral, and the central
sulfur is in the formal oxidation state 6+; and the terminal sulfur is in the
formal oxidation state 2-. This species is an important reducing agent. Ammonium
Thiosulphate is used as the most common component of photographic fixing agent
especially for rapid development. It is used as a nitrogen and sulphur
fertilizer. It is used to enhance N utilization efficiency of fertilizers such
as urea ammonium nitrate. Sodium Thiosulfate is a white translucent crystals or
powder that is common as the pentahydrate form; melting at 48 C; readily soluble
in water and oil of turpentine; aqueous solution is slightly alkaline which
decompose to sulfate and sulfide in the air. It is a moderate reducing agent.
Its major use is as a fixing agent in photography for developing film and the
extracting silver from ore. It is used in chrome-tanning leather and in chemical
manufacture as a source of sulfide ion. It is also used in paper, textile, water
treatment industry and gas purification.
Thiocyanate
is a salt or ester of thiocyanic acid (HSCN). Aqueous solutions of thiocyanic
acid , also called sulfocyanic acid, are very strong acids of the equilibrium
mixture of thiocyanic and isothiocyanic. Thiocyanates are bonded through the
sulfur(s) with the structure R-S-C≡N or the isomeric R-N=C=S (isothiocyanates).
Thiocyanates are bonded through the sulfur(s) which replace for the oxygen (O)
atom. Thiocyanates are the sulfur analog of isocyanates. Organic as well as
metallic thiocyanates [CuSCN, Ca(SCN)2, NaSCN, KSCN] are
very versatile compounds. They have wide range of applications including
manufacturing industrial chemicals, pharmaceuticals and pesticides. It is used
in freezing solutions, fabric dyeing, electroplating, steel pickling, printing,
and corrosion inhibitor against acid gases. It is used in photography industry
as a stabilizer or accelerator.
Thiourea
(also called Thiocarbamide or Sulfourea) is the diamide of thiocarbonic acid
that resembles urea but contains sulfur instead of oxygen. In fct, thiourea
occurs as the mixture of two tautomers: S=C(NH2)2 ( Thiourea) +
HS=CNHNH2 (Isothiourea),
accordingly, provides three functional groups (mino, imino, and thiol). Thiourea
is a lustrous white crystalline compound; estimated melting point is 170-180 C;
soluble in water and in polar organic solvents; insoluble in non-polar solvents.
The exact melting point and boiling point are not available since rearrangement
to ammonium thiocyanate (NH4SCN) occurs at about
135 C and decomposition occurs. It can be prepared by heating ammonium
thiocyanate, or by the addition of hydrogen sulfide to cyanamide. The latter is
the more common method. Thiourea is used directly in ore filtering, metal
refinery and cleaning, isomerization catalyst (conversion of maleic to fumaric
acid) and as an additive in fertilizers (to inhibit the nitrification process),
drilling auxiliaries, light-sensitive photocopy paper and explosives. It is
used as a fixing agent in photography, as a liquefying agent in animal hide
glue, as an insecticide, as a textile-treating agent, and as an intermediate to
produce other compounds. Thiourea and its derivatives are versatile
intermediates for the synthesis of modified thermosetting resins, thiourea
dioxide, dyes, flame retardants, vulcanization accelerators, plant protection
agents, pesticides, amino resins, peptizing agents, fungicides, hair
preparations, dry cleaning chemicals, corrosion inhibitors and thiazole drugs
(e.g., antiseptic, thyrotherapeutic, narcotic, and tuberculostatic agents).
Dithiobiurea possesses a wide dipole moment and thus is involved in the forming
wide metal chelated complexes as the radioactiv-compound which used in
radiopharmaceutical imaging, inhibiting enzyme function, kidney function study
and to treat toxic metal poisoning. It is used in co-crystals development used
in the field of nonlinear optics to generate new coherent wavelengths.
Thioglycolic
acid, a simple sulfur group- chained carboxylic acid, is a clear liquid; melts
at -16. c, boils at 96 C; soluble in water. It is an useful chemical
intermediate in the chemical reactions such as addition, elimination and
cyclization. Sulfur group will react with bases, acids, ketones and organic
halogen compounds, whereas the carboxylic group will preferentially react In the
presence of alcohols or amines. The applications of thioglycolic acid and its
derivatives are wide in the fields of of PVC stabilizers, down-hole acidizing,
corrosion inhibition in the oil field industry, manufacturing of
pharmaceuticals, agrochemicals and dyes, hair care products (waving, hair
removal and hair straightening), shrink-resistant treatment of wool, fabric
dying, leather processing.
Isethionic
acid, short chain alkan sulfonate containing hydroxy group, is a water soluble
liquid used in the manufacture of mild, biodegradable and high foaming anionic
surfactants which provides gentle cleansing and soft skin
feel. |