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The parent of porphyrins is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins. [ 1 ] With a total of 26 π-electrons, of which 18 π-electrons form a planar, continuous cycle, the porphyrin ring structure is often described as aromatic .
In the biosynthesis of porphyrins, the parent porphyrinogen is dehydrogenated by protoporphyrinogen oxidase. Because of their limited delocalization, porphyrinogens are colorless. Loss of all four central hydrogen atoms in the core yields a tetravalent anion that can act as a ligand to metal cations, creating a coordination compound . [ 3 ]
Porphine or porphin is an organic compound of empirical formula C 20 H 14 N 4. It is heterocyclic and aromatic . The molecule is a flat macrocycle , consisting of four pyrrole -like rings joined by four methine bridges, which makes it the simplest of the tetrapyrroles .
The general term protoporphyrin refers to porphine derivatives that have the outer hydrogen atoms in the four pyrrole rings replaced by other functional groups. The prefix proto often means 'first' in science nomenclature (such as carbon protoxide), hence Hans Fischer is thought to have coined the name protoporphyrin as the first class of porphyrins. [3]
The porphyrin with a core phosphorus (V) ion can be tuned with additional substituents added to either the outside of the polycyclic ring system or axially to the core phosphorus. Meso-substituted porphyrins like meso-tetra-p-tolylporphyrin (TTP) and octaethylporphyrin (OEP) are often used in synthesis of the core phosphorus porphyrin.
Porphyria / p ɔːr ˈ f ɪr i ə / is a group of disorders in which substances called porphyrins build up in the body, adversely affecting the skin or nervous system. [1] The types that affect the nervous system are also known as acute porphyria, as symptoms are rapid in onset and short in duration. [1]
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Here he detailed the synthesis of porphine, the fundamental ring system in all the porphyrins. He performed the porphin synthesis at a temperature of 90-95 °C and high pressure in sealed pyrex glass tubes, by reacting pyrrole, 2 % formaldehyde and pyridine in methanol for 30 hours. [7]