الكيمياء العضوية العملي

Elemental Analysis
Elemental Analysis is consider as an important step in the identification of
organic compounds. The chief elements making up organic compounds are carbon,
hydrogen and oxygen for which we do not employ chemical tests. Next to them in
order of importance are nitrogen , halogen (chlorine, bromine, and iodine ), and sulfur
that can be detected by reaction with sodium metal.
Sodium Fusion method
This method is used for detection of nitrogen, sulfur ,and halogen (N, S, and X).
The nonpolar nature of organic compounds makes the detection of N, S, and X
difficult because organic compounds do not ionize in solution to give ions of these
elements. For this reason it is necessary to convert these elements into inorganic ions
before doing the tests. The conversion is accomplished by heating a small quantity of
the organic compound with an equal quantity of metallic sodium. The organic
compound will decompose and soluble sodium salts of the elements will be formed.
C,H,O,N,X,S + Na NaCN,NaS,NaOH,NaX,NaSCN
Fusion
Sodium thiocyanide, NaSCN, is produced when both sulfur and nitrogen are
present in the same organic compound only when the quantity of sodium element is
small.
Sodium element is dangerous and extreme care should be exercised when handling
it since sodium element can react vigorously with water resulting in explosion.
Na + H2O NaOH
Therefore sodium element is kept dipped in liquid paraffin to prevent exposure to
moisture. The paraffin should be wiped off before using the sodium. It is also advised
not to touch it directly by hands since are usually moist resulting in burning
sensation. Note that sodium is a shiny element and when it is exposed to air and
moisture it is oxidized and become non shiny.