Carbon monoxide affinities with oxygen

AFFINITY. The tendency of an atom or compound to react or combine with atoms or compounds of different chemical constitution. For example, paraffin hydrocarbons were so named because they are quite unreactive, the word paraffin meaning very little affinity." The hemoglobin molecule has a much greater affinity for carbon monoxide Ilian for oxygen. The free energy decrease is a quantitative measure of chemical affinity. 

Neutron diffraction studies have shown that the outermost oxygen atom of the boxmd O2 is hydrogen bonded to the H atom on the atom of the distal imidazole ring of His E7 (Fig. 16-10). Carbon monoxide binds with the C=0 axis perpendicular to the heme plane and unable to form a corresponding hydrogen bond. This decreases the affinity for CO and helps to protect us from carbon monoxide poisoning. 

Carbon monoxide is neutral and only sparingly soluble in water. It forms metal carbonyls with transition metals. Its toxicity derives from the fact that hemoglobin (in the blood) has a far stronger affinity for carbon monoxide than for oxygen, which is essential for cell metabolism. 

Carbon monoxide, CO, has almost 200 times the affinity to bind with the hemoglobin, Hb, in the blood as oxygen. This means that hemoglobin will bind to carbon monoxide rather than oxygen in the body, if enough carbon monoxide is present in the blood, it can be fatai. 

The purpose of sodium nitrite (or amyl nitrite in the absence of IV access) is to produce methemoglobin, which binds cyanide with greater affinity than mitochondrial cytochromes. In the presence of decreased oxygen carrying capacity, as in combined exposures to cyanide and carbon monoxide (e.g., some fires), sodium nitrite can be detrimental and should be avoided. 

Carbon monoxide (CO) is generated in incomplete combustion processes. In households the main sources are all kinds of fuel burners (fuel oil, wood, natural gas, coal etc.) and automotive exhaust gas. Carbon monoxide is an odorless and invisible gas, and, due to its affinity to hemoglobin, which is higher than that of oxygen, it reduces the blood s capacity to carry oxygen. Hence it is toxic, especially for unborn and small children as well as for the elderly or people with heart problems or anemia. Even small amounts of CO can be harmful. Tab. 5.6 gives an overview of the relation between CO concentration and the corresponding symptoms of intoxication. 

The electron affinity of the metal surface is low in comparison with the tendency of the foreign molecule to receive electrons. This tendency is particularly high if the electron shell of the adsorbed molecule is incomplete (e.g. as in an oxygen atom) or if the bond of the atoms in the molecule is affected by an asymmetric electron shift (e.g, as in the molecules of nitrous oxide or carbon monoxide). In such cases the metal electrons become part of the electron shell of the foreign molecule. 

Carbon monoxide (CO), a colorless, odorless gas, is responsible for more than half of yearly deaths due to poisoning worldwide. CO has an approximately 250-fold greater affinity for hemoglobin than does oxygen. Consequently, relatively low levels of CO can have substantial and tragic effects. When CO combines with hemoglobin, the complex is referred to as carboxyhe-moglobin, or COHb. 

PREFERENTIAL. Descriptive of the selectivity of action, either chemical or physiochemical. exhibited by a substance when in contact with two other substances it may be due either to chemical affinity or to surface phenomena. An example of a preferential chemical combination is that of hemoglobin with carbon monoxide, with which it unites 200 times as readily as it does with oxygen when expose to a mixture of the two. Such phenomena as adsorption, corrosion, and the wetting of dry powders by liquids are other examples,... 

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