Organo-phosphorus compounds

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: 1837