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Thiourea
(also called Thiocarbamide or Sulfourea) is the diamide of thiocarbonic
acid that resembles urea but contains sulfur instead of oxygen. 'Thio'
is a chemical prefix indicates the replacement of an oxygen in an
acid radical by sulfur with a negative valence of 2; meaning 'Sulfur'
derived from the Greek theion. In fact, 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.
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