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In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate [2]) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula H C O − 3. Bicarbonate serves a crucial biochemical role in the physiological pH buffering system. [3]
The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of carbonic acid (H 2 CO 3), bicarbonate ion (HCO − 3 ), and carbon dioxide (CO 2 ) in order to maintain pH in the blood and duodenum , among other tissues, to support proper metabolic function. [ 1 ]
For the carbonic acid-bicarbonate buffer, a molar ratio of weak acid to weak base of 1:20 produces a pH of 7.4; and vice versa—when the pH of the extracellular fluids is 7.4 then the ratio of carbonic acid to bicarbonate ions in that fluid is 1:20. [14]
Carbonic acid monomers exhibit three conformational isomers: cis–cis, cis–trans, and trans–trans. [10] At low temperatures and atmospheric pressure, solid carbonic acid is amorphous and lacks Bragg peaks in X-ray diffraction. [11] But at high pressure, carbonic acid crystallizes, and modern analytical spectroscopy can measure its geometry.
Water is a very minor source of hydrogen ions in comparison to carbonic acid. Carbonic acid is formed from carbon dioxide and water by carbonic anhydrase. The bicarbonate ion (HCO 3 −) is exchanged for a chloride ion (Cl −) on the basal side of the cell and the bicarbonate diffuses into the venous blood, leading to an alkaline tide phenomenon.
Gastric acid is then secreted along with other gland secretions into the gastric pit for release into the stomach lumen. [2] The enzyme carbonic anhydrase catalyses the reaction between carbon dioxide and water to form carbonic acid. This acid immediately dissociates into hydrogen and bicarbonate ions.
Sodium bicarbonate can sometimes be used as a mild neutralization agent and a safer alternative to strong bases like sodium hydroxide. [79] Reaction of sodium bicarbonate and an acid produces a salt and carbonic acid, which readily decomposes to carbon dioxide and water: [79] NaHCO 3 + HCl → NaCl + H 2 O+CO 2 H 2 CO 3 → H 2 O + CO 2 (g)
Carbonation is the chemical reaction of carbon dioxide to give carbonates, bicarbonates, and carbonic acid. [1] In chemistry, the term is sometimes used in place of carboxylation, which refers to the formation of carboxylic acids. In inorganic chemistry and geology, carbonation is common.