Acids carbonic

Through an accident of history, the simplest dicarboxylic acid, carbonic acid, HOCOH, is not even classihed as an organic compound. Because many minerals are carbonate salts, nineteenth-century chemists placed carbonates, bicarbonates, and carbon dioxide in the inorganic realm. Nevertheless, the essential features of carbonic acid and its salts are easily understood on the basis of our knowledge of carboxylic acids. 

Carbonic acid is formed when carbon dioxide reacts with water. Hydration of carbon dioxide is far from complete, however. Almost all the carbon dioxide that is dissolved in water exists as carbon dioxide only 0.3% of it is converted to carbonic acid. Carbonic acid is a weak acid and ionizes to a small extent to bicarbonate ion. 

The systematic name for bicarbonate ion is hydrogen carbonate. Thus, the systematic name for sodium bicarbonate (NatiCOj) is sodium hydrogen carbonate. 

The equilibrium constant for the overall reaction is related to an apparent equilibrium constant Ki for carbonic acid ionization by the expression 

These equations tell us that the reverse process, proton transfer from acids to bicarbonate to form carbon dioxide, will be favorable when of the acid exceeds 4.3 X 10 (pA a 6.4). Among compounds containing carbon, hydrogen, and oxygen, only carboxylic acids are acidic enough to meet this requirement. They dissolve in aqueous sodium bicarbonate with the evolution of carbon dioxide. This behavior is the basis of a qualitative test for carboxylic acids. 

The value cited for Ki of carbonic acid, 4.3 x 1(T, is determined by measuring the pH of water to which a known amount of carbon dioxide has been added. When we recall that only 0.3% of carbon dioxide is converted to carbonic acid in water, what is the true Ki of carbonic acid  

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Carbon dioxide (CO2) is a very common contaminant in hydrocarbon fluids, especially in gases and gas condensate, and is a source of corrosion problems. CO2 in the gas phase dissolves in any water present to form carbonic acid (H2CO3) which is highly corrosive. Its reaction with iron creates iron carbonate (FeCOg) ... 

The corrosion rate of steel in carbonic acid is faster than in hydrochloric acid Correlations are available to predict the rate of steel corrosion for different partial pressures of CO2 and different temperatures. At high temperatures the iron carbonate forms a film of protective scale on the steel s surface, but this is easily washed away at lower temperatures (again a corrosion nomogram is available to predict the impact of the scale on the corrosion rate at various CO2 partial pressures and temperatures). 

The amount of carbonic acid present, undissociated or dissociated, is only about 1 of the total concentration of dissolved carbon dioxide. Carbonic acid, in l especi of its dissociation into hydrogen and hydrogencarbonate ions, is actually a stronger acid than acetic acid the dissociation constant is ... 

Since carbonic acid is a weak acid, its salts are hydrolysed in aqueous solution ... 

Urea (the diamide of carbonic acid) can be prepared by the historic method of Wohler. When an aqueous solution of ammonium cyanate is allowed to stand, the cyanate undergoes molecular rearrangement to urea, and an equilibrium mixture containing about 93% of urea is thus formed. Urea is... 

Carbonic anhydrase red blood corpuscles carbonic acid CO, and H,0 6-8... 

The exchange resins 6nd application in (i) the purification of water (cation-exchange resin to remove salts, followed by anion-exchange resin to remove free mineral acids and carbonic acid), (ii) removal of inorganic impurities from organic substances, (iii) in the partial separation of amino acids, and (iv) as catalysts in organic reactions (e.g., esterification. Section 111,102, and cyanoethylation. Section VI,22). 

Supplement (combined with Volume IV) III, 2nd 1929 195-449 Hydroxy-carboxylic acids Carbonic acid, 3. GlycoUic acid, 228. Lactic acid, 261. Tartaric acid, 481. Citric acid, 556. Urea, 42. Cyanamide, 74. Thiocyemic acid, 140. 

Protonated and diprotonated carbonic acid and carbon dioxide may also have implications in biological carboxylation processes. Although behavior in highly acidic solvent systems cannot be extrapolated to in vivo conditions, related multidentate interactions at enzymatic sites are possible. 

Bromomethyl-l-adamantyl ketones were condensed with thioamides of carboxylic or carbonic acids to give the corresponding thiazoles (613). 

The carbon m methane has the lowest oxidation number (—4) of any of the com pounds m Table 2 4 Methane contains carbon m its most reduced form Carbon dioxide and carbonic acid have the highest oxidation numbers (+4) for carbon corresponding to Its most oxidized state When methane or any alkane undergoes combustion to form carbon dioxide carbon is oxidized and oxygen is reduced A useful generalization from Table 2 4 is the following... 

Recall that when carbonic acid IS formed as a reaction product It dissociates to car bon dioxide and water... 

Through an accident of history the simplest dicarboxylic acid carbonic acid HOCOH IS not even classified as an organic compound Because many minerals are carbonate... 

As with other dicarboxyhc acids the second ionization constant of carbonic acid IS far smaller than the first... 

Section 19 9 Carbon dioxide and carbonic acid are m equilibrium m water Carbon dioxide IS the major component... 

Phenol IS a weaker acid than carbonic acid The equilibrium shown lies to the left... 

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