Hydrogen carbonate ions

Hydroxide ion lies below phenol m Table 1 7 hydrogen carbonate ion lies above phe nol The practical consequence of the reactions shown is that NaOH is a strong enough base to convert phenol to phenoxide ion but NaHCOs is not... 

Many important biochemical reactions involve Lewis acid Lewis base chemistry Carbon dioxide is rapidly converted to hydrogen carbonate ion m the presence of the enzyme carbonic anhydrase... 

Verify that the position of equilibrium for the reaction between phenol and hydroxide ion lies to the right by comparing the pK of the acid on the left to the acid on the right. Which acid is stronger Do the same for the reaction of phenol with hydrogen carbonate ion. 

E Carbonic acid H2C03) Hydrogen carbonate ion (HC03-) 4.4 x 10-7 6.36... 

FIGURE 10.2 Stalactites hang from the roof of a cave and stalagmites grow from the floor. Both are made of insoluble calcium carbonate formed from the soluble hydrogen carbonate ions in groundwater. 

The Bronsted definition also includes the possibility that an ion is an acid (an option not allowed by the Arrhenius definition). For instance, a hydrogen carbonate ion, HC03, one of the species present in natural waters, can act as an acid and lose a proton, and the resulting carbonate ion is removed by precipitation if suitable cations are present (Fig. 10.2) ... 

The body maintains blood pH by two primary mechanisms respiration and excretion. Carbonic acid concentration is controlled by respiration as we exhale, we deplete our system of CO, and hence deplete it of H2C03, too. This decrease in acid concentration raises the blood pH. Breathing faster and more deeply increases the amount of C02 exhaled and hence decreases the carbonic acid concentration in the blood, which in turn raises the blood pH. Hydrogen carbonate ion concentration is controlled by its rate of excretion in urine. 

Metabolic acidosis is caused by the release into the bloodstream of excessive amounts of lactic acid and other acidic byproducts of metabolism. These acids enter the bloodstream, react with hydrogen carbonate ion to produce H2CX)5, and shift the ratio HC03 /H2C03 to a lower value. Heavy exercise, diabetes, and fasting can all produce metabolic acidosis. The normal response of the body is to increase the rate of breathing to eliminate some of the CO,. Thus, we pant heavily when running uphill. 

The main buffer in the blood consists primarily of hydrogen carbonate ions (HC03 ) and H30 + ions in equilibrium with water and C02 ... 

Sodium hydrogen carbonate, NaHC03 (sodium bicarbonate), is commonly called bicarbonate of soda or baking soda. The rising action of baking soda in batter depends on the reaction of a weak acid, HA, with the hydrogen carbonate ions ... 

In the human body, carbon dioxide provides the buffer. This is called the carbonic acid-hydrogen carbonate ion buffer system. This buffer system maintains the body s blood pH within acceptable levels. The main threat to the bloods pH is excess hydrogen ions produced by various chemical reactions in the body. When hydrogen ions are produced, hydrogen carbonate ions in the blood pick them up and convert them to carbonic acid ... 

The electrochemical oxidation is often more sensitive to the reaction conditions than to the substituents. Platinum electrodes are recommended for methoxylation and the equivalent acetoxylation procedures.290 In acetonitrile buffered by hydrogen carbonate ion, 3,4-diethylfuran affords the 2,5-dihydroxy-2,5-dihydro derivative (84%) and Jones oxidation readily leads to diethylmaleic anhydride in what is claimed to be the best general method for such conversions.291 In unbuffered methanol and under current density control, the oxidation of 2-methylfuran appears to eliminate the methyl group since the product is the acetal-ester 111 also obtained from methyl 2-furoate.292 If sodium acetate buffer is used, however, the methyl group is retained but oxidized in part to the aldehyde diacetate 112 in a... 

O A sample of blood was taken from a patient and sent to a laboratory for testing. Chemists found that the blood pH was 7.40. They also found that the hydrogen carbonate ion concentration was 2.6 x 10 mol/L. What was the concentration of carbonic acid in the blood ... 

Buffers are extremely important in biological systems. The pH of arterial blood is about 7.4. The pH of the blood in your veins is just slightly less. If the pH of hlood drops to 7.0, or rises above 7.5, life-threatening problems develop. To maintain its pH within a narrow range, blood contains a number of buffer systems. The most important buffer system in the blood depends on an equilibrium between hydrogen carbonate ions and carbonate ions. Dissolved carbon dioxide reacts with water to form hydrogen carbonate ions. 

The principal buffer system in blood serum is based on the equilibrium between carbonic acid, H2C03(aq), and the hydrogen carbonate ion, HCO3 . Carbonic acid is unstable, however. It is also in equilibrium with carbon dioxide. Therefore, a second equilibrium reaction is involved in the hydrogen carbonate buffer system in the blood the reaction between carbon dioxide and water to produce carbonic acid, and its reverse. The two equilibrium reactions are summarized below. 

Assume that carbonic acid and hydrogen carbonate ions are the only contributors to blood pH. 

It is conceivable that iron could be stored in the form of a complex such as transferrin or even hemoglobin, and in lower organisms ferrichrome apparently serves this purpose. Such storage is wasteful, however, and higher animals have evolved a simpler method of storing iron as ferritin. If iron(lll) nitrate is allowed to hydrolyze in a solution made slightly basic by the hydrogen carbonate ion (HCOJ-), it spontaneously forms spheres of FeOOH" of about 7000 pm in diameter. The core of a ferritin particle is similar and contains up to 4500 iron atoms and apparently some... 

---