Utente:Grasso Luigi/sanbox1/ossicloruro di rame
| Grasso Luigi/sanbox1/ossicloruro di rame | |
|---|---|
 | |
| Nome IUPAC | |
| triidrossocloruro di dirame | |
| Nomi alternativi | |
| cloruro di rame basico | |
| Caratteristiche generali | |
| Peso formula (u) | 213,56 |
| Aspetto | solido verde-azzurro[1] |
| Numero CAS | |
| Proprietà chimico-fisiche | |
| Densità (g/cm3, in c.s.) | 3,64[1] |
| Solubilità in acqua | praticamente insolubile[1] |
| Temperatura di fusione | >220 °C (493 K) dec[1] |
| Proprietà tossicologiche | |
| DL50 (mg/kg) | 700 oral rat[1] |
| Indicazioni di sicurezza | |
| Simboli di rischio chimico | |
 
| |
| pericolo | |
| Frasi H | 301 - 332 - 410 [1] |
Dicopper chloride trihydroxide is the chemical compound with the formula Cu2(OH)3Cl. It is often referred to as tribasic copper chloride (TBCC), copper trihydroxyl chloride or copper hydroxychloride. It is a greenish crystalline solid encountered in mineral deposits, metal corrosion products, industrial products, art and archeological objects, and some living systems. It was originally manufactured on an industrial scale as a precipitated material used as either a chemical intermediate or a fungicide. Since 1994, a purified, crystallized product has been produced at the scale of thousands of
tons per year, and used extensively as a nutritional supplement for animals.
Natural occurrence
modificaCu2(OH)3Cl occurs as natural minerals in four polymorphic crystal forms: atacamite, paratacamite, clinoatacamite, and botallackite. Atacamite is orthorhombic, paratacamite is rhombohedral, and the other two polymorphs are monoclinic. Atacamite and paratacamite are common secondary minerals in areas of copper mineralization and frequently form as corrosion products of Cu-bearing metals.[2] [3]</ref>[4][5][6][7][8]
The most common Cu2(OH)3Cl polymorph is atacamite. It is an oxidation product of other copper minerals, especially under arid, saline conditions. It was found in fumarolic deposits, and a weathering product of sulfides in subsea black smoker deposits. It was named for the Atacama Desert in Chile. Its color varies from blackish to emerald green. It is the sugar-like coating of dark green glistening crystals found on many bronze objects from Egypt and Mesopotamia. It has also been found in living systems such as the jaws of the marine bloodworm Glycera dibranchiate. The stability of atacamite is evidenced by its ability to endure dynamic regimes in its natural geologic environment.[3][4][5] [9]
Paratacamite is another Cu2(OH)3Cl polymorph that was named for the Atacama Desert in Chile. It has been identified in the powdery light-green corrosion product that forms on a copper or bronze surface – at times in corrosion pustules. It can be distinguished from atacamite by the rhombohedral shape of its crystals.[3][4][7]
Botallackite is the least stable of the four Cu2(OH)3Cl polymorphs. It is pale bluish-green in color. This rare mineral was first found, and later identified, in the Botallack Mine in Cornwall, England. It is also a rare corrosion product on archaeological finds. For instance, it was identified on an Egyptian statue of Bastet.[3][4][6]
The fourth polymorph of Cu2(OH)3Cl family is clinoatacamite. It was found and identified around in Chuquicamata, Chile in 1996. It was named in allusion to its monoclinic morphology and relationship to atacamite. It too is pale green but has monoclinic crystals. Clinoatacamite can be easily confused with the closely related paratacamite. It is believed that clinoatacamite should replace most previously reported occurrences of paratacamite in the conservation literature.[3][4][8]
Struttura
modifica
Nella figura accanto si notano cristalli alpha puri dell'ossicloruro di rame.
L'atacamite è ortorombica, gruppo spaziale Pnma, con due unità asimmetriche cristallograficamente indipendenti contenenti Cu e atomi ossigeno del gruppo idrossile. Entrambi i due atomi Cu mostrano una geometria di coordinazione caratteristica Jahn-Teller ottaedrale distorta (4+2): ogni Cu è legato ai quattro gruppi OH vicini con distanze Cu-OH di 2.01Å; inoltre, un degli atomi Cu è legato ai due atomi Cl (a 2.76Å) formando l'ottaedro [Cu(OH)4Cl2], e l'altro Cu e' legato ad un atomo Cl (a 2.75Å) e un gruppo OH (a 2.36Å) formando l'ottaedro [Cu(OH)5Cl]. I due tipi di ottaedro sono collegati agli spigoli per formare una struttura tridimensionale con l'ottaedro [Cu(OH)5Cl] che incrocia l'altro ottaedro [Cu(OH)4Cl2] in strati paralleli a (110) (Fig 1). [3] [4][5]
Botallackite crystallizes in monoclinic with space group P21/m. Like in atacamite, there are two different types of Cu coordination geometries: Jahn-Teller distorted octahedral [Cu(OH)4Cl2] and [Cu(OH)5Cl]. But these octahedra assemble in different ways. Each octahedron shares six edges with surrounding octahedra, forming a two-dimensional sheet-type structure parallel to (100). The adjacent sheets are held together by hydrogen bonding between the hydroxyl oxygen atoms of one sheet and the opposing chlorine atoms in the other sheets. The resulting weak bonding between the sheets accounts for the perfect (100) cleavage and the typical platy habit of botallackite (Figure 2).[3][4][6]
Paratacamite is rhombohedral, space group R3. It has a well-developed substructure with a’=a/2, c’=c, apparent space group R3m. There are four crystallographically independent Cu atoms in the asymmetric unit. The Cu atoms display three different types of octahedral coordination geometries. Three quarters of the Cu atoms are coordinated to four near OH groups and two distant Cl atoms, giving the expected (4+2) configuration [Cu(OH)4Cl2]. Three sixteenths of the Cu atoms are bonded to two near OH groups at 1.93Å and four stretched OH groups at 2.20Å to form an axially compressed (2+4) octahedral [Cu(OH)6], and the remaining one sixteenth of the Cu atoms are bonded to six equivalent OH groups at 2.12Å to form a regular octahedral [Cu(OH)6]. The Jahn-Teller distorted [Cu(OH)4Cl2] octahedra share the edges and form partially occupied layers parallel to (001), and the compressed and regular [Cu(OH)6] octahedra cross-link the adjacent [Cu(OH)4Cl2] octahedral layers to form a three-dimensional framework. The existence of the regular octahedral [Cu(OH)6] is unusual, and it has been shown that partial substitution of Zn or Ni for Cu at this special site (3b) is necessary to stabilize paratacamite structure at ambient temperature. Due to the high symmetry of the special position, only about 2 wt% Zn is necessary to stabilize the rhombohedral structure. In fact, most of paratacamite crystals studied contain significant amounts of Zn or Ni (>2 wt%) (Figure 3).[3][4][7]
Clinoatacamite is monoclinic, space group P21/m. The structure is very close to that of paratacamite. But the [Cu(OH)6] octahedron is Jahn-Teller distorted. The Jahn-Teller distorted [Cu(OH)4Cl2] octahedra share the edges to form partially occupied layers parallel to (101). This layer is topologically the same as that in mica. Adjacent layers of octahedra are offset, such that vacant sites in one sheet align with occupied sites in the neighboring sheet. The [Cu(OH)6] octahedra link the layers to form a 3-dimensional network (Figure 4).[3][4] [8]
Thermodynamic data based on the free energy of formation indicates that the order of stability of these polymorphs is clinoatacamite>atacamite> botallackite. Spectroscopic studies show that the strength of hydrogen bonding in these polymorphs is in the order paratacamite >atacamite> botallackite. Studies on the formation of basic copper chloride indicate botallackite is a key intermediate and crystallizes first under most conditions; subsequent recrystallization of botallackite to atacamite or paratacamite depends on the nature of reaction medium.[10] [11][12]
Note
modifica- ^ a b c d e f GESTIS 2018
- ^ Richardson, H. W. Ed., Handbook of Copper Compounds and Applications. Marcel Dekker, Inc., New York, NY, U.S.A., 1997, 71.
- ^ a b c d e f g h i handbookofmineralogy
- ^ a b c d e f g h i Webmineral sito web: (a) Atacamite(b) Botallackite c) Paratacamite (d) Clinoatacamite
- ^ a b c (a) Wells, A. F. The crystal structure of atacamite and the crystal chemistry of cupric compounds. Acta Crystallogr. 1949, 2, pp.175-80. (b) Paris, J. B; Hyde, B. G. The structure of atacamite and its relationship to spinel. Crystal. Struc. Comm. 1986, C42(10), pp.1277-80.
- ^ a b c Hawthorne, F. C. Refinement of the crystal structure of botallackite. Mineral Mag. 1985, 49, 87- 89.
- ^ a b c FLeet, M.E. The crystal structure of paratacamite, Cu2(OH)3Cl. Acta Crystallorg. 1975, 831, 183-187.
- ^ a b c (a) Jambor, J. L.; Dutrizac, J. E.; Roberts, A. C.; Grice, J. D.; Szyma´nski, J. T. Clinoatacamite, a new polymorph of Cu2(OH)3Cl, and its relationship to paratacamite and “anarakite”. Can. Mineral. 1996, 34, 61–72; (b) Grice, J.D.; Szyma´nski, J. T.; Jambor, J. L. The crystal structure of clinoatacamite, a new polymorph of Cu2(OH)3Cl. Can. Mineral. 1996, 34, 73–78.
- ^ (a) Lichtenegger, H. C.; Schöberl, T.; Bartl, M. H.; Waite, H.; Stucky, G. D. High Abrasion Resistance with Sparse Mineralization: Copper Biomineral in Worm Jaws. Science 2002, 298 (5592), 389 – 392; (b) Lichtenegger, H. C.; Birkedal, H.; Casa, D. M.; Cross, J. O.; Heald, S. M.; Waite, H.; Stucky, G. D. Distribution and Role of Trace Transition Metals in Glycera Worm Jaws Studied with Synchrotron Microbeam Techniques. Chem. Mater. 2005, 17, 2927-2931
- ^ Frost, R. Raman spectroscopy of selected copper minerals of significance in corrosion. Spectrochimica acta. Part A: molecular and biomolecular spectroscopy 2002, 59(6), 1195-1204.
- ^ Sharkey, J. B.; Lewin, S. Z. Thermochemical properties of the copper (II) hydroxychlorides. Thermochimica Acta 1972, 3(3), 189.
- ^ Pollard, A. M.; Thomas, R. G.; Williams, P. A. Synthesis and stabilities of the basic copper (II) chlorides atacamite, paratacamite, and botallackite. Mineral Mag. 1989, 53, 557-563.
Bibliografia
modifica- [a) Atacamite (b) Botallackite (c) Paratacamite(d) Clinoatacamite Web], su handbookofmineralogy.org.
