Chemical Trap
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In
chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, a chemical trap is a
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
that is used to detect unstable compounds. The method relies on efficiency of bimolecular reactions with reagents to produce a more easily characterize trapped product. In some cases, the trapping agent is used in large excess.


Case studies


Cyclobutadiene

A famous example is the detection of cyclobutadiene released upon oxidation of
cyclobutadieneiron tricarbonyl Cyclobutadieneiron tricarbonyl is an organoiron compound with the formula Fe(C4H4)(CO)3. It is a yellow oil that is soluble in organic solvents. It has been used in organic chemistry as a precursor for cyclobutadiene, which is an elusive species i ...
. When this degradation is conducted in the presence of an alkyne, the cyclobutadiene is trapped as a bicyclohexadiene. The requirement for this trapping experiment is that the oxidant (ceric ammonium nitrate) and the trapping agent be mutually compatible. :


Diphosphorus

Diphosphorus Diphosphorus is an inorganic chemical with the chemical formula . Unlike nitrogen, its lighter pnictogen neighbor which forms a stable N2 molecule with a nitrogen to nitrogen triple bond, phosphorus prefers a tetrahedral form P4 because P-P pi-bo ...
is an old target of chemists since it is the heavy analogue of N2. Its fleeting existence is inferred by the controlled degradation of certain niobium complexes in the presence of trapping agents. Again, a Diels-Alder strategy is employed in the trapping: :


Silylene

Another classic but elusive family of targets are silylenes, analogues of carbenes. It was proposed that dechlorination of dimethyldichlorosilane generates dimethylsilylene: :SiCl2(CH3)2 + 2 K → Si(CH3)2 + 2 KCl This inference is supported by conducting the dechlorination in the presence of trimethylsilane, the trapped product being pentamethyldisilane: :Si(CH3)2 + HSi(CH3)3 → (CH3)2Si(H)-Si(CH3)3 Not that the trapping agent does not react with dimethyldichlorosilane or potassium metal.


Related meanings

In some cases, chemical trap is used to detect or infer a compound when present at
concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...
s below its detection limit or is present in a mixture, where other components interfere with its detection. The trapping agent, for example a dye, reacts with the chemical to be detected, giving a product that is more easily detected.


References

{{Reflist Analytical chemistry