Overview
Copper(II) hydroxide, also called cupric hydroxide, is an inorganic compound with the formula Cu(OH)2. It typically appears as a pale blue to blue-green solid that can be produced as a precipitate when a soluble copper(II) salt is treated with a base. The compound contains copper in the +2 oxidation state coordinated to hydroxide anions. For a general reference see copper(II) hydroxide information.
Structure and properties
In its common forms, Cu(OH)2 is a polymeric material in which each copper ion is surrounded by oxygen atoms from hydroxide ligands; the local geometry is often distorted octahedral because of electronic effects. It is sparingly soluble in water, decomposes on heating to copper(II) oxide (CuO) and water, and reacts with acids to give soluble copper(II) salts. Important chemical behaviors include complexation by ammonia to yield deep blue ammine complexes and gradual conversion to oxide on drying or prolonged standing. See chemical and physical properties at reference.
Preparation and reactions
Laboratory preparation is commonly achieved by adding a solution of a hydroxide (for example, sodium hydroxide) to a solution of a soluble copper(II) salt such as copper sulfate, producing a characteristic blue precipitate. Cu(OH)2 undergoes thermal decomposition to CuO and reacts with ligands and acids; for example, treatment with concentrated ammonia forms the tetraamminecopper(II) complex. More details on synthetic methods are available at preparation notes.
Uses and applications
Copper(II) hydroxide finds use as a fungicide and bactericide in agriculture, as a precursor for other copper compounds, and occasionally as a pigment or laboratory reagent. In crop protection it is used where copper-based control of fungal disease is desired and appears in some formulations and mixtures. Industrial and research uses exploit its reactivity toward acids, ligands and thermal conversion; see applications summary at applications.
Distinctions and safety
Cu(OH)2 is chemically distinct from copper(I) oxide, copper(II) oxide (CuO) and basic copper salts; it should not be confused with complex copper hydroxide minerals. Handling precautions are typical for metal hydroxides and copper compounds: avoid inhalation and ingestion, and minimize skin contact. For safety data and handling guidance consult safety information.