Dicarbonate
Introduction The general structure of dicarbonate estersMolecular structure of bis(trifluoromethyl) dicarbonateA '''dicarbonate''', also known as a '''pyrocarbonate''', is a chemical containing the divalent  or  functional group, which consists of two carbonate groups sharing an oxygen atom. These compounds can be viewed as derivatives of the hypothetical compound '''dicarbonic acid''',  or . Two important organic compounds containing this group are dimethyl dicarbonate  and di-''tert''-butyl dicarbonate .It is one of the oxocarbon anions, consisting solely of oxygen and carbon. The anion has the formula  or . Dicarbonate salts are apparently unstable at ambient conditions, but can be made under pressure and may have a fleeting existence in carbonate solutions.The term ''dicarbonate'' is sometimes used erroneously to refer to bicarbonate, the common name of the hydrogencarbonate anion  or esters of the hydrogencarbonate functional group . It is also sometimes used for chemicals that contain two carbonate units in their covalent structure or stoichiometric formula.
Inorganic salts  (lead(II) dicarbonate) can be formed at 30 GPa and 2000K from PbCO3 and CO2.It forms white monoclinic crystals, with space group ''P''21/''c'' and four formula units per unit cell. At 30 GPa the unit cell has a=4.771 b=8.079 c=7.070 Å and β=91.32°. The unit cell volume is 272.4 Å3 and density 7.59. (strontium dicarbonate) is very similar to the lead compound, and also has monoclinic structure with space group ''P''21/''c'' and four formula units per unit cell. At 30 GPa the unit cell has a=4.736 b=8.175 c=7.140 Å and β=91.34°. The unit cell volume is 276.3 Å3 and density 4.61.The double Sr=O bonds have lengths of 1.22, 1.24, and 1.25 Å. The single Sr-O bonds have lengths of 1.36 and 1.41 Å. The angles subtended at the carbon atoms are slightly less than 120°, and the angle at the C-O-C is larger.
See also *Boc anhydride*Tricarbonate*Peroxodicarbonate*Oxalate*Pyrosulfate*Peroxydisulfate*Dithionate*Trithionate*Tetrathionate*Pyrophosphate*Polyphosphate
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