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Iodine is a
nonmetallic halogen element in Group 17 of periodic table; atomic number 53;
atomic mass 126.9; melting point ca 114 C; boiling point ca 184 C; specific
gravity 4.93 g/cm3; oxidation states: 7,5,1,-1; [Kr] 4d10 5s2 5p5.
Iodine is a nearly black poisonous, corrosive solid at room temperature and
readily sublimes to a deep violet vapour, the colour of which is responsible for
its name from Greek. It is insoluble in water, soluble in common solvents.
Iodine is required in small amounts in human body for the function of the
thyroid gland. Iodine forms many important compounds of iodine such as
iodine(V)oxide, potassium iodide, iodine trichloride and iodoform of an Iodine
containing organic compound.
The related
name, iodate indicates any salt of iodic acid containing the
IO3- radical;
KIO3 (potassium iodate)
and NaIO3 (sodium iodate) are
the most important salts. Whereas, iodide indicates any compound of iodine with
a more electropositive element or group such as such as
CH3CH2I or any binary
compound of iodine which may contain the I- radical and which may
be considered to be derived from hydriodic acid (HI); KI and NaI are examples.
Organic
iodines are very useful reagents as they have lower heat of formation than
chlorine or bromine analogues. Aliphatic Iodides are used as alkylating agents
in synthetic organic chemistry. Iodoform is a simple structural compound;
greenish yellow hexagonal solid with a strong, penetrating odor; containing
about 96 per cent of iodine; melting point 119 C; soluble in chloroform and
ether and somewhat in alcohol and water: used as a topical anti-infective,
applied to the skin. Iodoacetic acid is used in biochemical research; it
alkylates free thiol groups but not disulfide bridges. methyl iodide, also
called iodomethane, is a colorless liquid that turns brown on exposure to light;
used in microscopy and in testing for pyridine. It is irritating to skin and
mucous membranes and is a suspected carcinogen. Ethylene diamine dihydroiodide
is used in animal feeds to prevent deficiency of iodine. Iodine organic
compounds are useful in dye industry for the high bright colors as well as
pharmaceutical industry. They are important for the production of X-ray contrast
media and for the formulating antiseptics. n-Butyl iodide, clear
liquid; boiling at 130 C, is used as an alkylating agent in organic synthesis
for many application, for example, as solvents, intermediates for numerous
chemicals, dyes, fumigants, sterilants, X-ray contrast media, antiseptics, insecticides, quaternary ammonium compounds, flavours and fragrances and
pharmaceuticals. |
