Oxalic Acid
(also called Ethanedioic Acid) is a colourless, crystalline, toxic organic
compound belonging to the family of dicarboxylic acids; melting at 187 C;
soluble in water, alcohol, and ether. It occurs in the form of its metal salts
(usually calcium or potassium) in many plants. It is commercially manufactured
by heating sodium formate in the presence of an alkali catalyst to form sodium
oxalate, which should be converted to free oxalic acid when treated with
sulfuric acid. It is also prepared by oxidizing carbohydrates with nitric acid,
by heating saw dust with caustic alkalies or by fermentation of sugar solutions
in the presence of certain molds. Oxalic acid is the only possible compound in
which two carboxyl groups are joined directly; for this reason oxalic acid is
one of the strongest acids in organic compounds. Unlike other carboxylic acids,
oxalic acid (and formic acid) is readily oxidized and combine with calcium,
iron, sodium, magnesium, or potassium to form less soluble salts called
oxalates. Oxalic acid and oxalates are useful as reducing agents for
photography, bleaching, and rust removal. They are widely used as an purifying
agent in pharmaceutical industry, precipitating agent in rare-earth metal
processing, bleaching agent in textile and wood industry, rust-remover for metal
treatment, grinding agent, waste water treatment. acid rinse in laundries and
removing scale from automobile radiators.
Hydrazine (anhydrous) is a clear, fuming, corrosive liquid with an ammonia-like
odor; melting at 1.4 C, boiling at 113.5 C, specific gravity 1.011. It is very
soluble in water and soluble in alcohol. It decomposes on heating or exposure to
UV to form ammonia, hydrogen, and nitrogen, which may be explosive with a blue
flame when catalysed by metal oxides and some metals such as platinum or Raney
nickel. It is prepared from ammonia with chloramine in the presence of glue or
gelatin (to inhibit decomposition of the hydrazine by unreacted oxidants) as the
hydrate form usually (100% monohydrate contains 64% by weight hydrazine).
Hydrazine is also prepared from sodium hypochlorite with urea in the presence of
glue or gelatin. Botht ammonia and amines are nitrogen nucleophiles which
donate electrons (they are Lewis bases). But hydrazine (diamine) has much
stronger nucleophilicity which makes it more reactive than ammonia. Hydrazine
has dibasic and very reactive properties. Hydrazine is used as a component in
jet fuels because it produce a large amount of heat when burned. Hydrazine is
used as rocket fuel. Hydrazine is used as an oxygen scavenger for water boiler
feed and heating systems to prevent corrosion damage. Hydrazine is used as a
reducing agent for the recovery of precious metals. It is used as a
polymerization catalyst and a chain extender in urethane coatings. It and its
derivatives are versatile intermediates. They have active applications in
organic synthesis for agrochemicals, pharmaceuticals, photographic, heat
stabilizers, polymerization catalysts, flame-retardants, blowing agents for
plastics, explosives, and dyes. Recently, hydrazine is applied to LCD (liquid
crystal displays) as the fuel to make faster thin-film transistors. Hydrazide is an acyl hydrazine. Acyl (-CO) is an organic radical formed by
removal of a hydroxyl group from an organic acid (carboxyl group).
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