Hydroxyl reaction with metal ions

Reaction with metal ions is related to the antioxidant activity of phenols. For example, flavonoids with two hydroxyl groups in... 

Reactions. Because it contains both a carboxyl and a primary hydroxyl group, glycolic- acid can react as an acid or an alcohol or both. Thus some of the important reactions it can undergo are esterification, umidation. salt formation, and complexation with metal ions, which lead to many of its uses. As a fairly strong acid it can liberate gases (often toxici when il reacts wilh Ihe corresponding salts. 

Two metal ions (typically, participate in the DNA polymerase reaction. One metal ion coordinates the 3 -hydroxyl group of the primer, whereas the other metal ion interacts only with the dNTP. The phosphate group of the nucleoside triphosphate bridges between the two metal ions. The hydroxyl group of the primer attacks the phosphate group to form a new O—P bond. 

Cuprous ions (Cu+) also react with hydrogen peroxide to make hydroxyl radicals (Halliwell and Gutteridge, 1985). The presence of iron salts and cuprous ions in the formulation can lead to an accelerated photochemical degradation of the drug by these reaction mechanisms. Metal ions can also participate in redox reactions with the drug or excipients in the preparation, depending on the redox properties of the species involved. Such reactions may further influence photochemical stability of the product, e.g., by the formation of photosensitizers. 

Finally, the substitution of Pt by BDD leads to a dramatic enhancement of the oxidation ability of the Fenton-based EAOPs, as observed for the pesticide 2,4-dichlorophenoxyacetic acid in Fig. 2. At present, BDD is the best anode material to oxidize organic pollutants, since it yields a high concentration of physisorbed hydroxyl radicals (BDD( OH)) at a very positive anode potential from reaction (7). Therefore, in the EF with BDD, the refractory organic molecules and their complexes with metal ions can be oxidized by the combined action of BDD( OH) formed at the anode and OH produced in the bulk. 

Phospholipids can form salts, for example with metal ions, due to the presence of one free hydroxyl group of the bound phosphoric acid in phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol and two free hydroxyl groups in phosphatidic acid. Mostly, calcium and magnesium ions are involved in these reactions, but the resulting complexes have hydrophobic character, as in metal soaps. Cations of heavy metals (copper, manganese and iron) bound in phospholipids catalyse autoxidation significantly less than free metal ions, phospholipids can thus become synergists of antioxidants. 

Proper electron delocalization is thus important. Furthermore, the presence of a hydroxyl group for chelation with metal ions appears essential. Surprisingly, with a-phenyl-a-aminomalonic acid in the presence of Cu(II) and appropriate model compounds (see below), an oxidation reaction takes place which has no biological precedent (303). 

The homogeneous type macromolecule-metal complex is synthesized by the reaction of synthetic or natural polymers containing donating groups, such as hydroxyl, carboxylic acid, ketone, phosphoric acid, amine, heterocyclic nitrogen, or thiol, with metal ions. The typical polymeric ligands are... 

Reactions of the Hydroxyl Group. The hydroxyl proton of hydroxybenzaldehydes is acidic and reacts with alkahes to form salts. The lithium, sodium, potassium, and copper salts of sahcylaldehyde exist as chelates. The cobalt salt is the most simple oxygen-carrying synthetic chelate compound (33). The stabiUty constants of numerous sahcylaldehyde—metal ion coordination compounds have been measured (34). Both sahcylaldehyde and 4-hydroxybenzaldehyde are readily converted to the corresponding anisaldehyde by reaction with a methyl hahde, methyl sulfate (35—37), or methyl carbonate (38). The reaction shown produces -anisaldehyde [123-11-5] in 93.3% yield. Other ethers can also be made by the use of the appropriate reagent. 

---