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Copper benzoate describes chemical compound with the formulaCu(C 6H 5CO 2) 2(H 2O) n. They consist of coordination complexes derived from the cupric ion and the conjugate base of benzoic acid. Many derivatives are known with diverse ancillary ligands.[3]
Copper(II) benzoate exists in at least two structural forms, depending on the degree of hydration. Resembling copper(II) acetate, one form of copper benzoate adopts a "Chinese lantern" structure,[4] 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.[5] A hydrated form is also known, wherein each Cu(II) centre is bound to four water ligands and a bidentate O, O-benzoate.[6]
Preparation
Trihydrate
Copper benzoate trihydrate can be made by combining aqueous solutions of sodium benzoate and copper sulfate, forming a pale blue precipitate:[7]
4 K(C 6H 5CO 2) + 2 CuSO 4· 5H2O → Cu 2(C 6H 5CO 2) 4(H 2O) 2 + 2 K 2SO 4 + 8 H 2O
Anhydrous forms
The "α form" of the anhydrous compound is prepared by vacuum desiccation of the trihydrate at 95 °C with phosphorus pentoxide.[7] The "β form" is obtained by heating the monoethanol derivative in air at 90 °C.[7] The "γ form" is obtained by heating the monoethanol derivative in boiling carbon tetrachloride for a few hours.[7] All are described as "blue-green crystalline powders."
Uses
It has found some niche use as a combination fuel and source of copper ion for blue light production in fireworks.[8] It is not on the list of chemicals approved in consumer fireworks in the US.[9]
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.[1]
Related compounds
Tetrakis[copper(I) benzoate]
A tetrakis[copper(I) benzoate] has been characterized.[10][11]
Addition compounds
Copper(II) benzoate forms many addition compounds. Examples include copper(II) benzoate mono(benzoic acid) and the adducts with ethanol and urea.[7]
↑Wells, A. F. (1984). Structural inorganic chemistry (5th ed.). Oxford [Oxfordshire] : New York: Clarendon Press; Oxford University Press. pp. 1131. ISBN0-19-855370-6.
↑Kawata, T.; Uekusa, H.; Ohba, S.; Furukawa, T.; Tokii, T.; Muto, Y.; Kato, M. (1 June 1992). "Magneto-structural correlation in dimeric copper(II) benzoates". Acta Crystallographica Section B Structural Science48 (3): 253–261. doi:10.1107/S0108768191012697.
↑Koizumi, Hideo; Osaki, Kenji; Watanabé, Tokunosuké (1963). "Crystal Structure of Cupric Benzoate Trihydrate Cu(C6H5COO)23H2O". Journal of the Physical Society of Japan18 (1): 117–124. doi:10.1143/JPSJ.18.117. Bibcode: 1963JPSJ...18..117K.