Comparison is made between organo-phosphorus and organo-nitrogen compounds, because both phosphorus and nitrogen are in Group 5A of the periodic table. Thus, they are similar in character. But unlike nitrogen, phosphorus is not able to form multiple bonds with carbon. However, it can form very strong double bonds with oxygen. Oxygen, in turn, forms strong bonds with carbon, enabling phosphorus to make strong, indirect bonds with carbon. Further important properties of organo-phosphorus compounds include their ability to react with acids. Phosphorus is useful and
Organic chemistry: Organo-sulfur, -phosphorus, and -metal compounds 93
important in a variety of other organic (carbon-based) compounds.
Organo-phosphorus compounds play an important part in the transfer of energy within biological organisms. Adenosine is a substance found in tissue (especially muscle tissue) and inside cells. It is important in muscle contraction and the metabolism (conversion into energy) of sugar. Adenosine triphosphate (ATP) is a compound of adenosine and three phosphate groups (organo-phosphorus compounds). ATP is the most important carrier of energy in living cells. The transfer of a phosphate group to another molecule releases large amounts of energy. During this chemical process, the ATP becomes ADP (adenosine diphosphate). ADP is a compound of adenosine and two phosphorus groups. If this chemical reaction takes place in muscle tissue, the energy released is used for the contraction of muscles. This happens, for example, during walking or the clapping of hands. If the chemical reaction with ATP occurs inside a cell, the energy released is used to fuel a metabolic process that sustains life. This is a process that turns food into energy and living tissue.
Essential though phosphorus is in living systems, it can also threaten them. The nerve gases Sarin and Tabun are phosphorus compounds. Nerve gases cause extreme weakness, even death. They do so by restraining an enzyme that is essential in triggering nerve impulses. With this enzyme neutralized, the muscles and metabolic activities inside cells can no longer be "turned on." Eventually, even breathing is affected, and the affected organism dies. Some phosphorus-based insecticides act essentially in the same way. The principal ones are malathion and the parathions. A special feature of these insecticides is the speed with which they decay in the environment. Thus, they present little threat to people and animals.
Date: 2015-12-11; view: 1220