chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

, 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 Cyclobutadiene is an organic compound with the formula . It is very reactive owing to its tendency to dimerize. Although the parent compound has not been isolated, some substituted derivatives are robust and a single molecule of cyclobutadiene is ...

released upon oxidation of

cyclobutadieneiron tricarbonyl Cyclobutadieneiron tricarbonyl is an organoiron compound with the formula Fe(C4H4)(CO)3. It is a yellow solid that is soluble in organic solvents. It has been used in organic chemistry as a precursor for cyclobutadiene, which is an elusive specie ...

. 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

silylene Silylene is a chemical compound with the formula SiH2. It is the silicon analog of methylene, the simplest carbene. Silylene is a stable molecule as a gas but rapidly reacts in a bimolecular manner when condensed. Unlike carbenes, which can exis ...

s, analogues of carbenes. It was proposed that dechlorination of

dimethyldichlorosilane Dimethyldichlorosilane is a tetrahedral, organosilicon compound with the formula Si(CH3)2Cl2. At room temperature it is a colorless liquid that readily reacts with water to form both linear and cyclic Si-O chains. Dimethyldichlorosilane is made ...

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 Trimethylsilane is the organosilicon compound with the formula (CH3)3SiH. It is a trialkylsilane. The Si-H bond is reactive. It is less commonly used as a reagent than the related triethylsilane, which is a liquid at room temperature. Trimethyls ...

, 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'', an ...

s below its

detection limit The limit of detection (LOD or LoD) is the lowest signal, or the lowest corresponding quantity to be determined (or extracted) from the signal, that can be observed with a sufficient degree of confidence or statistical significance. However, the ...

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