Copper benzoate


Copper benzoate is the chemical compound with the formula. These coordination complexes are derived from the cupric ion and the conjugate base of benzoic acid. Many derivatives are known with diverse ancillary ligands. It has found some niche use as a combination fuel and source of copper ion for blue light production in fireworks.

Preparation

In laboratory, copper benzoate can be made by combining aqueous solutions of potassium benzoate with copper sulfate. Hydrated copper benzoate precipitates as a pale blue solid:

Uses

It is sometimes used by hobbyists as a fuel and blue flame colorant in pyrotechnics, but it is not on the list of chemicals approved in consumer fireworks in the US.
It is also used in two-part dental adhesives, in polyester resin compositions to increase thermal resistance and decrease gelation, and as a metal-based hydrogen sulfide scavenger in asphalt.

Structure

Copper benzoate exists in at least two structural forms, depending on the degree of hydration. As in copper(II) acetate, one form of copper benzoate adopts a "Chinese lantern" structure, wherein a pair of copper centers are linked by four bridging carboxylate ligands. Typically, one site on each copper center is occupied by water, which can be replaced by other ligands. A hydrated form is also known, wherein each Cu centre is bound to four water ligands and a bidentate O, O-benzoate.

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